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Volume 19, 1886

III.—Geology.

Art. XLI.Narrative of an Ascent of Ruapehu.

[Read before the Wellington Philosophical Society, 24th February, 1886.]

During the progress of a recent geological survey of this district, I had occasion to ascend Mount Ruapehu, and, by permission of the Director, I am now enabled to place before you an account of my trip.

Ruapehu is the highest mountain in this island, attaining a height of almost 9,000 feet above the sea. It is situated at the southern extremity of the great volcanic chain that extends north to Lake Taupo, and occupies a most prominent and central position, being almost equidistant from the sea on three sides. It reaches far above the snow-line of this latitude, and maintains immense snow-fields throughout the year, this being perhaps as much due to its huge massive character as to its height.

It is the source of many large and important rivers, the principal of which are the Waikato, which drains its eastern slopes and falls into the sea some distance south of the Manukau Harbour; the Wangaehu, with its large tributary the Mangawhero, which drains its southern slopes and discharges into Cook Strait; and the Manganui-a-te-ao, which rises on the west side of Parataetaitonga, and joins the Wanganui about 8 miles above Pipiriki.

The first ascent of Ruapehu appears to have been made by Sir George Grey,* but I am unable to ascertain the precise date; however, it must have been previous to 1867.

The present ascent was made on the 8th January of this year, or about two and a half months earlier than any previous ascent, as far as I can learn. I was accompanied by Mr. Dunnage, Mr. A. D. Wilson's cadet, who was sent with me to erect a signal on the summit for triangulation purposes, and also by Dalin, a survey hand.

We left Karioi on the 7th January, and the same evening pitched our camp at the foot of Ruapehu, at about 4,000 feet above the sea. Our intention was to have pushed on to the top

[Footnote] * “Hochstetter's N.Z.,” 1867, p. 378.

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edge of the bush; but, as this was the highest point at which we could find water and grass for the horses, we were unable to proceed further, and made up our minds to make up the lost distance by an earlier start next day.

On the morning of the 8th we were astir at daylight, and before the sun had risen were far up the mountain's side. A sharp walk of two hours brought us to the first patch of snow, at a height of 5,500 feet. The distance travelled was about 3 miles, over low ascending rocky ridges.

The ascent so far was not steep, and only rendered difficult by the numerous deep rocky water-courses that had to be crossed. These were generally dry, but in early spring they must be roaring torrents, judging from the great size of the rock masses strewn in their channels and piled high on their sides.

At 6,500 feet we encountered permanent snow-fields. The ascent now became steeper and more difficult, and but for the sun's rays softening the surface snow we could not have proceeded. Each member of the party was equipped with a properly-shod alpenstock and heavy nailed boots, and by means of these we were able to ascend places that otherwise were impossible to us.

Our intention was to have worked our way round the south side of the mountain to the great snow-field lying between the south-east peak, facing Karioi, and the south peak, the highest part of Ruapehu, known by the native name, Parataetaitonga, and then followed up this to the summit. However, we were unable to do this, for on reaching this field we found the snow frozen so hard that we were unable to dig our alpenstocks into it, or to make steps that could be considered safe, taking into account the steepness of the ascent. In order not to lose time we proceeded straight up the south-east peak. The ascent was exceedingly steep, and very slow, as great care had to be exercised in making steps and securing a firm hold with our alpenstocks. Several narrow rocky ridges cropped out on our route, but they had to be carefully avoided, as the slightest touch was often sufficient to send a shower of loose rocks flying across the snow, to the imminent danger of the whole party.

After a slow and trying ascent of three hours, the summit of the peak was reached, and it was not without some anxiety that we hastily examined the saddle between us and the highest peak, for it was quite evident to all that it would be next to impossible to return by the way we had come, on account of the steepness of the snow.

The saddle, or more properly “côl,” lay about 450 feet below us, and how to reach it was difficult to determine. The northern side of the peak we were on presented a perfectly perpendicular wall of bare rock, being too steep to carry snow, while on its southern side the snow was frozen too hard to

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obtain a foothold, and, choosing the least of two dangers, we spent an hour vainly trying to descend the rocky wall on the northern side, by zigzaging from ledge to ledge. In this fashion we succeeded in reaching within 50 feet of the foot of the precipice, but here our further progress was barred by a mass of smooth, polished pitchstone porphyry that had withstood frost and snow, and offered no ledges or projections by which to descend. Again ascending to the summit of the peak, we sat down to deliberate, and soon afterwards we found that the sun had softened the snow on the south side, so that with extra caution we were able to descend to the saddle. Once on the saddle, we made rapid progress, but a sharp lookout had to be kept for the numerous crevasses and fissures which, in places, cut the ice into an intricate network, more especially where the snow-fields were moderately flat. The saddle, being narrow, was corniced on the north side, which was the steepest, and care had to be taken not to walk too close to the edge. Having passed the saddle, we began the ascent of the main peak.

Being now able to ascend from the south side, from the great snow-field previously mentioned, we made up for lost time; but it was not all “plain sailing.” When not more than 250 feet from the summit we encountered a wall of ice about 20 feet high, which we failed to surmount, although repeated attempts were made.

Without wasting much time here we turned to the northeast aspect of the mountain, and continued the ascent from that direction. The sun had left that side some time, and the snow, that an hour before was dripping under the sun's strong rays, had now commenced to freeze—not into a solid cohesive mass, but into loose icy particles. In crossing this snow-field the greatest care had to be taken not to start this layer of dry snow, which continually showed signs of sliding on the smooth surface of the hard ice below.

Proceeding rapidly, but as lightly as possible, so as not to start a snow-slip, we made for a high boss of volcanic agglomerate, near which we knew the snow would still be moist enough to adhere to the ice.

All went well till within a few yards of the rocks, when, in some way or other, Dunnage lost his footing and began to slide down the snow-field at a terrific rate. His destruction seemed inevitable, for he was rapidly approaching an immense crevasse that traversed the whole field, and had particularly attracted our attention a short time before. It was the dangerous description of crevasse well known to alpine tourists, which has one side higher than the other. In this case the drop was on the low side, and was about 20 feet. The width of the crevasse at the top was about 15 feet, and both sides were corniced, and from its concave

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roof and sides hung innumerable long blue icicles and sharp projections of ice. Its depth appeared to be many hundreds of feet, extending probably to the bottom of the valley. To this crevasse Dunnage was rapidly sliding, and there seemed but small chance of his recovering himself. He was sliding with his back to the snow, and his weight started the dry snow, which accelerated his speed; but he had fortunately stuck to his alpenstock, which, getting in front of him, ploughed into the ice, so that eventually he was able to swing himself clear of the sliding snow; but none too soon, for with a few feet more he would have dashed into the icy chasm below. The distance he slid was about 200 feet.

After a brief rest, the ascent was continued, but with greater care; and without further mishap we reached the summit of Parataetaitonga, which was covered with snow to a great depth, giving a fine rounded outline to the peak.

The outlook from Ruapehu on a clear day must be very extended; but, unfortunately, the whole country round was filled with black smoke from the numerous large bush fires which were then raging on the south side of the forest belt. The smoke did not rise higher than 6,500 feet, and, above this, all was sunshine and brightness, the only object standing out of the dark sea being the white shining peak of Mount Egmont, 80 miles to the westward.

Immediately below us lay the great crater of Ruapehu, encircled by high peaks from 500 to 800 feet high. The crater proper, or what was probably the former vent, is situated not in the centre of the basin, but appears to be nearer to Parataetaitonga than the northern or western peaks. The vent, as far as could be judged from our high position, is probably ten chains across. At this time it was occupied by a great sheet of ice, of a bluish colour, and there was no appearance of steam or water.

On its south-east side the great crater-basin, which is perhaps a mile across, is partially broken down, and connects with an immense snow-field, at the foot of which, at 6,000 feet, the Wangaehu as a considerable stream is first seen. The waters of this river, when they emerge from their ice-bound source, have a yellowish milky colour, and emit a strong sulphurous smell.

As there was little to be gained by a prolonged stay on the top, we hastily erected a trig, signal, which consisted of a stout birch sapling, driven into the snow several feet, and a ball of black calico. Our names, with the date of ascent, were placed in a sealed bottle, and left in a cairn of stones, on a rock-ledge about a chain to the north of the summit, and about 15 feet lower.

We now began the descent. By this time the sun's rays had left the south-east slopes, and a hard crust of frozen snow

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had formed; but by stamping with our heels this was easily broken through. After reaching the saddle, or “côl,” we descended by the great snow-field between the south-east peak facing Karioi and the main peak, which we were unable to ascend in the morning on account of its frozen surface. This field reaches down to 6,000 feet, and is traversed by numerous crevasses; but these were successively avoided, and in little more than half an hour we reached the lowest limits of the snow. In descending the field “glissading” was resorted to, as on account of the steepness this rapid mode of progression was found to be the easiest and safest.

A rough, difficult walk of two hours, over a tumbled and confused mass of rocks brought us back to our camp.

For several days afterwards Mr. Dunnage and Dalin suffered severely from snow-blindness, the fierce glare of the sun on the glistening snow having induced acute inflammation of the eyes.

Art. XLII.Notes in reference to the Prime Causes of the Phenomena of Earthquakes and Volcanoes.

[Read before the Wellington Philosophical Society, 25th August, 1886.]

The recent outburst of volcanic activity in the Lake District naturally excites our curiosity in relation to the prime cause of earthquakes and volcanic phenomena; and I propose, in this paper, to call attention to some points which appear to me materially to affect the solution of this question, but which are not referred to, so far as I have been able to ascertain, in any geological works. In order, however, that the bearing of the matters to which I am about to call attention may be understood, it is necessary that I should refer, in the first place, to the speculations of astronomers and physicists respecting the original condition of our globe as a concrete mass, because, if those speculations be well founded, it is clear that the phenomena of earthquakes and volcanoes must be associated with the continued existence of fused matter at no great depth below its surface.

Herschel long ago pointed out how, under the action of gravitation, cosmical matter “so diffused as to be scarcely discernible” might be condensed into a comparatively small mass. Kant, in his “Naturgeschichte des Himmels,” (published in 1755), assumed that all the materials composing the spheres that

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belong to our solar world were, in the beginning of all things, resolved into their elementary substance, and filled the whole space of the system in which these spheres now move. Laplace, who is said to have been ignorant of Kant's hypothesis, published his “Exposition du Système du Monde” in 1796, in which he referred the formation of our planetary system to a gradual cooling and contraction of the atmosphere of the sun, contending that this atmosphere previously extended, under the influence of excessive heat, beyond the orbits of the farthest planets. Mayer, in his “Celestial Dynamics,” (published in 1848), tells us that the Newtonian theory of gravitation, whilst it enables us to determine, from its present form, the earth's state of aggregation in the past, at the same time points to a source of heat powerful enough to produce such a state of aggregation, and teaches us to consider the molten state of a planet as the result of the condensation of cosmical matter, and to derive the radiant heat of the sun and the heat of the bowels of the earth from the same sources. Those who are curious as to these speculations will find a criticism of the various phases which the Nebular Hypothesis, as a cosmogenetic theory, has assumed, in Stallo's “Concepts and Theories of Modern Physics,” published as vol. xlii. of the International Scientific Series, in which the objections to each of the views propounded in relation to this hypothesis are pointed out and discussed. But the general idea that our planetary system originated from the condensation of cosmical matter has been confirmed by, or at all events receives strong support from, our recently acquired knowledge of the present condition of two of the largest of its members,—namely, Jupiter and Saturn, and of that of our own satellite. As to the latter, it is abundantly proved, that it is composed of the cooled relics of a once intensely heated mass, its whole surface giving evidence of extinct eruptive action. The absence of any appreciable atmosphere around it leaves that surface permanently unchanged, the ruggedness of the ejected material in no degree effaced, or even moderated, by the distribution of light volcanic ash, if any such substance happens to exist upon it, of which I have considerable doubt. We also now know that each of the two great outer planets, Jupiter and Saturn, is still in a condition of intense heat throughout its whole mass. “We recognize,” says Mr. Proctor, “in the appearance of Jupiter the signs of as near an approach to the condition of the earth, when as yet the greater part of her mass was vaporous, as is consistent with the vast difference between two orbs containing such unequal quantities of matter;” and the same author, speaking of the “great red spot” which has, for some years past, excited the attention and curiosity of astronomers, says: “It may well be that the movements by which a disturbed cloud-belt on Jupiter returns to its normal condition

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are sluggish, compared with the fierce action by which disturbances are brought about at, or it may be below, the fiery surface of the planet itself.”

I think, indeed, that it may almost be received as a postulate, that, in whatever manner the cosmical matter of which our globe was formed became aggregated, it must, for a very long period after that aggregation had been completed, have remained in a condition of intense heat at its surface.

I have already dealt with this subject in papers on the “Cause of warmer climates which existed in high northern latitudes during former geological epochs,” published in the 10th volume of the “Transactions of the New Zealand Institute,” to which I may refer any person desirous of going more fully into it, and I do this without hesitation, because the views contained in those papers were received with approval by several scientific inquirers of high position and authority in Europe. In the first of those papers I remarked that geologists, including so eminent an authority as the late Sir Charles Lyell, have hitherto treated such speculations as those I have referred to as having only a remote bearing on geology; but I cannot help thinking, that so long as we continue to recognize the extent to which the surface conditions of the earth have been, and are still being modified by the action of forces operating at great depths below that surface, and especially by such exhibitions of those forces as earthquakes and volcanoes, we are bound to be guided in our inquiries by a regard to those speculations, before we can hope to arrive at any sound understanding of the phenomena in question.

I must not, however, in justice to Dr. Page, one of the most delightful writers on geology, omit to refer to some remarks which he makes in his “Advanced Text-book,” in relation to these speculations. In dealing with the question of the density of our globe, he points out that it cannot, if the law of gravitation be acting uniformly towards the centre, be composed throughout of materials in the same condition as those which constitute its crust, because, in that case, a depth would soon be arrived at where the density of ordinary rocks would become so great as to give a mean density much higher than that which its astronomical relations seem to warrant. He also points out that, whilst the ponderable crust, calculating from precession and nutation, cannot be of less thickness than a fourth or fifth of the radius, (being about that assigned to it by Hopkins, as I mention further on), the interior layers of that crust may consist of molten rock-matter, or even rock-matter in a state of vaporiferous incandescence. He then says that, whatever be the exact proportions and conditions of the crust and interior of the earth, we know enough of its temperature to warrant certain general conclusions—namely, that the surface temperature is

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mainly derived from the sun, and may, though variable and irregular, be laid down with some degree of certainty; that the heat thus derived extends to a depth of from 60 to 90 feet, and that below this stratum the temperature increases at such a rate, that a temperature must soon be reached sufficient to keep in fusion the most refractory rock-substances; that this high internal temperature is apparently the cause of hot springs, volcanoes, earthquakes, and other igneous phenomena which make themselves known at the surface. In another passage he says: “Looking at the comparative thinness of the solid crust, one can readily conceive how much it would be affected by any commotion in the interior zones, or by any contraction or expansion of the entire mass. Hence the tremors, the undulations, the upheavals and subsidences occasioned by earthquakes and volcanic convulsions; and hence, also, the fissures and fractures which everywhere traverse the rocky crust, whether they may have arisen from the efforts of local forces, or from the operations of some unknown but general law of secular contraction.”

I do not propose to enter into a discussion of the causes which may have brought about the present figure of the Earth, because, except in so far as that figure adds strength to the view of its original fluidity from heat, it does not materially affect the question under consideration; but I propose to make some observations on this subject in the sequel, in order to show its connection with the special matter dealt with in this paper. It is curious, however, that amongst physicists who have accepted the nebular hypothesis as a sound cosmological theory, considerable differences of opinion have been expressed as to the mode in which the cooling of our globe commenced. As mentioned by Sir Charles Lyell in his “Elements of Geology,” Poisson controverted the doctrine of the present high temperature of the central nucleus, and declared his opinion that, if the globe had ever passed from a fluid to a solid condition in consequence of the loss of heat by radiation, the cooling and consolidation of the surface would have begun at the earth's centre, or, in other words, that the aggregation was so slow as to admit of the dynamical heat generated in the act being radiated into space as fast as it was generated. Other physicists treat the cooling as having commenced at and extended downward from the surface of the completely aggregated mass, and, whilst admitting that the nucleus may still be in a fluid state, have assigned a very great thickness to the solidified crust. Hopkins has fixed this at from 800 to 1,000 miles at the least, whilst others have treated the fact, that the mean density of the earth exceeds that of the rocks which compose the known portions of the crust by 2 ½ to 3, as justifying the assumption that the nucleus consists chiefly of solidified metallic substances. Dr. Page has, however, given the most conclusive reasons against

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the validity of such an assumption, if we are to admit that the increase in temperature found to obtain as we penetrate the crust below the stratum of invariable temperature continues beyond the depths to which our observations have extended, for it is clear that, in such case, the temperature reached at the depth of 25 miles would be sufficient to fuse nearly all the rockmaterial with which we are acquainted, whilst at the depth of 150 miles all such material would be reduced to a state of vaporiform incandescence.

Now it is very singular that, notwithstanding the admitted connection of this internal heat with the phenomena of earthquakes, volcanic disturbances, upheavals and subsidences which affect the outer crust of the earth, some very important investigations made by Messrs. Nasmyth and Carpenter, in connection with their long-continued and exhaustive examination of the surface conditions of the moon, appear to have been entirely overlooked by geological writers, although Nasmyth and Carpenter distinctly pointed out that the results of their investigations would most probably be found to have an important bearing on the origin of the phenomena referred to, and tend to show that the thickness of the solidified, and especially of the rigid, portion of the crust, must be very much less than that which has been generally assigned to it.

I will now proceed to give some idea of the nature of those investigations, and of their suggested bearing upon the matters referred to.

Messrs. Nasmyth and Carpenter were induced, as one of the results of their long and careful observations of the surface of the moon, to inquire into the relative densities of fusible matters in the fluid and solid conditions. They found that, with few exceptions,—exceptions having no influence upon the questions at issue,—all fusible substances solid at ordinary temperatures are densest when molten. They found that solid gold, silver, iron, copper, and other metals floated upon the same substances in the molten state; that solid slag floated on melted slag, and so forth; thus accounting, in part at all events, for the greater density of the deeper portions of the globe's mass, assuming those portions to be still in a fluid condition from heat. They pointed out, what is indeed a corollary to the first proposition, that molten material, solid at ordinary temperatures, expands to and attains its minimum density in the act of solidifying, and that this expansion is followed by contraction as the solidified matter afterwards parts with its heat by radiation. Thus, if the tire of a wheel has to be formed as a casting, the fused metal must in the first place be poured into a suitable mould, in which provision has been made for the expansion of the solidifying matter. After it has cooled sufficiently to become rigid, and to

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bear removal from the mould without warping, but whilst still retaining a great degree of expansion from heat, it must be taken from the mould and placed in position round the wheel to which it is to form the tire. At first it is loose, but rapidly tightens by contraction, as it gradually parts with its heat by radiation, or, as is more usual, as it is cooled by the application of douches of cold water. I am not aware to what extent the density of fusible substances can be increased when in the solid condition by the mere lowering of their temperatures, but I doubt whether the density of any such substance, whatever pressure it may be subjected to, (the heat generated by such pressure being withdrawn), can be thus increased so as to bring it up to that which it possesses in the molten state.

It will be seen, therefore, that in proportion to the heat to which they are exposed, within the limits, in the descending scale, of the lowest degree of temperature known to us on the one hand, and the state of complete fusion on the other, metallic and earthy fusible substances undergo three well-marked changes in density—namely, they have a maximum when fused, a minimum when first solidified, and an intermediate density when their heat in the solid condition is reduced by radiation.

Now, assuming that the Earth was at one time in a molten state, it is clear that so soon as it had parted with sufficient heat to admit of the solidification of its outer surface, the material so solidified would at once expand, and in course of time would pass from the plastic to a rigid state. As radiation proceeded further, the exposed surface would cool to such a degree as to cause contraction of its substance, which would then press with great force upon the less rigid solid material between it and the still molten mass below. But that molten mass would still continue to part with its heat by conduction and radiation, and its surface would solidify; and, indeed, this process would necessarily be continuous, until the rigid crust had reached such a thickness as to oppose further solidification. Until this point had been reached, however, the consequences of the processes to which I have referred would be to create constant strains upon the contracted and still contracting outer portions of the crust, and, as a result of such strains, the production of fissures, or bulgings, or foldings, according to the degree of rigidity to which it had attained. A further effect would be to create cavernous spaces at various depths, and of greater or less extent, into which masses of molten matter would be injected by the pressure created upon the nucleus by the plastic material interposed between it and the contracted outer crust. Matter so injected would solidify with greater rapidity than that which remained in general contact with the fluid mass, and its expansion would certainly produce more violent action on the surface of the globe than would result from the more

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gradual solidification of films on the surface of the diminishing nucleus.

The effect of the operations referred to upon the ultimate form of a spherical mass of fused matter, occupying the position and having the motions of the Earth, would, I think, be to produce, or, at all events, materially to assist in producing, the form which the Earth now presents. Radiation from such a mass would, in the absence of any local compensating action, be equal from every part of the surface; but from the moment that a fixed axis of rotation had been established under the paramount influence of the Sun's attraction, that radiation would proceed most rapidly at the poles, diminishing gradually towards the equator.

The result of the more rapid radiation in circumpolar regions would be to reduce the sphere to a spheroid, by the pressure of the contracting outer crust within those areas upon the molten internal mass, which, in its turn, would necessarily press outwards upon the more plastic materials in equatorial regions, until equilibrium had been established. This view is supported by the distribution of volcanoes on the surface of the Earth: for, with the exception of Hecla, in Iceland, in latitude 65° North, and Mount Erebus, on the Antarctic Land, in about the same latitude South, active volcanic action is most intense within tropical regions, and extends but little into the limits of the temperate zone. This fact appears to indicate that the loss of heat which the earth originally sustained, and is still suffering, is largely compensated within the tropics, and for some distance on each side of them, by that which it receives from the sun's radiation, and, consequently, that the molten material in the interior of the earth is exposed, within that area, to pressure less effective to prevent earthquakes and resulting volcanic phenomena, than it is subject to within the circumpolar and immediately adjacent regions.

It is, no doubt, difficult to apply the mind to the consideration of operations such as these in connection with a mass of such enormous dimensions as our globe; but it is very clear that, with the exception of the cooling of its surface to such a degree as to cause any great amount of contraction, operations of this very nature must now be going on in the great planet Jupiter. I cannot say to what extent the dynamical heat, generated by the condensation of the cosmical matter of which that planet is composed, and which is being lost by radiation into space, is compensated from outer sources. Those who are curious on this subject may consult the views propounded by Mr. Mattieu Williams, in his work on “The Fuel of the Sun,” and the very similar views as to the maintenance of the sun's heat propounded by the late Sir W. Siemens in the columns of “Nature.” It is clear, however, that in the case of our globe,

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whatever retarding effect its atmosphere may have exercised upon the cooling of the outer crust, that cooling was comparatively rapid, although the straining effects which I assume to have resulted from the causes referred to were still powerful enough, in Tertiary times, to result in the elevation of nearly if not all the great mountain chains now existing upon it. Whether the forces in question are still equal to bringing about changes in the surface similar to those which are revealed to us by the investigations of geologists as having occurred since the commencement of the Eocene period, can only be determined in the far distant future, although I am inclined to doubt it.

The straining referred to has, however, certainly not ceased, and will not cease until the thickness of the earth's rigid crust has become sufficiently great to prevent further solidification of the molten interior matter. The diminution which has apparently taken place in the intensity of volcanic action since the close of the Miocene period, seems to indicate the approach of such a condition of things, and that time, when it does arrive, will certainly be the commencement of the period in which the earth will attain its ultimate surface conditions.

Art. XLIII.On the Cause of Volcanic Action.

[Read before the Hawke's Bay Philosophical Society, 13th September, 1886.]

Abstract.

The first section of this paper reviews at length the arguments in favour of the dynamical theory for the origin of volcanic force, and the opinions accepted by the author may be summarized as follows:—

The conversion into heat of the work expended on the crushing and other internal rearrangement of rocks, (generally as subordinate phenomena in mountain elevation), by horizontal pressures produced in the crust of the earth by its sinking upon a retreating nucleus, under the action of gravity, is the efficient source of volcanic heat of all degrees of intensity. The pressures, and the effect of their conversion into heat, may be roughly calculated. A specimen calculation shows the pressures required to elevate a mountain range 120 miles wide, 3 ½ miles high above its supporting base, and from a crust 56 miles thick, must be 340 tons per square inch, the work of which, converted into heat, would raise the temperature of any mass of silica within which it acted by about 4,200° Fah., and other rocks in

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proportion to their specific heat. The pressures needed to lift a mountain 20 miles wide and 1 mile in average height above its base, from a crust 20 miles thick, would be about 270 tons per inch, giving a temperature, if converted into heat, within silica, of 3,348°. In neither case is the initial temperature of the rock taken into account. The fusion of rock and extrusion of lava are the more important geologically, but it is not necessary that rock should be fused to give rise to volcanic phenomena. Temperatures of 550° and 1,000°, which would not affect a rock, give steam pressures of 1,000lbs. and 4 tons per inch, respectively, either of which, but especially the latter, would have great disruptive or explosive power, provided a vent was opened for them. The writer contends that volcanic steam, or fused rock, cannot open their own way to the surface; this must be provided for them by the movements which produce the heat fissuring the rocks above. He contends, also, that volcanic steam results from the heating of a wet rock; that violent eruptive phenomena cannot be caused by the access of water to heated rocks. It is suggested that in steam eruptions, (such as that at Tarawera), the steam in escaping tears and crumbles up the free surface of the heated rock as frost acts on a clay bank: hence the fineness of the bulk of the ejecta. A rule is found to hold good in so many cases as to be worth further study—that volcanoes only appear where upheaving forces have acted about more than one axis, the volcanoes being found, not where the lines intersect, but in one or more of the angles formed by them.

The paper then proceeds to offer a history of the recent outbreak at Tarawera, on the lines thus laid down:—

Crust pressures, acting (as shown by the great fissure-lines) upon an axis lying north-east and south-west, accumulated in the elastic compression of certain beds until they were able to bring about movements of some kind in the rocks within which they acted, and which were at no great depth beneath the surface, but whose extent and thickness I make no attempt to estimate. During a fortnight or more before the outbreak these movements were going on, as was shown by the earthquakes experienced in the locality. (That the focus of action was situated at no great depth is indicated by the fact that the shocks were merely local.) The movements affected a considerable mass of wet rock, and were only effected by the exertion of considerable force. Judging from the resulting great amount of the ejections, it is probable that the action involved such a deformation of some part of the area of rock compressed as would have amounted to crushing at the surface, and the heat developed in such a case would be proportional to the force employed in the crushing. While this was going on below, the upper rocks were being cracked and fissured by the movements. The line of crushing appears to have passed under the Tarawera, or very

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near it, and the first fissure made available for the escape of steam from the heated beds passed through one side of the mountain. (It is not unlikely that the mountain was plentifully fissured and creviced beforehand.) On a way being opened for the escape of the steam, it was promptly taken advantage of. For some time the force of the steam would be largely employed in tearing away the sides of and enlarging the vent, the product of this action being the larger stones described as underlying the sand and dust on and near the mountain. All this time, as afterwards during the continuance of the eruption, the steam in escaping from the heated rock (which was possibly crushed, certainly weakened in its cohesion), would tear off and crumble off its “face,” and carry the fragments out through the fissure, to scatter them to the winds.

There is no evidence, I understand, that any portion of the ejecta had been fused, but the fineness of the great mass indicates that the rock from which it was derived was very thoroughly crushed by the movement which heated it, by the escaping steam tearing it to pieces, or by both actions together.

The subterranean rock movements continued, as indicated by continued earthquakes; the fissure through the upper beds was extended, and a second set of eruptions set up further south, the subterranean action being similar to the first. In connection with this second eruption, I should like to offer a suggestion as to the cause of certain noises that have been described as “horrible roarings,” that ceased after a time, by those who were unfortunate enough to be in Wairoa on that memorable night. These may have been common volcanic sounds, but they may not. One of the chief centres of the second eruption was Lake Rotomahana, from the bed of which very copious ejections took place. Now one of the most horrible noises I ever heard is that caused by the condensation of steam within a body of water, as when a locomotive-driver turns a steam jet into his water-tank—a measure of economy when his steam is blowing off. Exchange the locomotive-tank for a lake, or quarter-inch pipe for an aperture possibly some yards in area, and 150lbs. pressure for, say, 1,000lbs., and one can imagine a cause for the “horrible roarings” heard at Wairoa. This noise would cease as soon as the escaping steam had carried up material enough to construct a cone, or cones, to the surface of the lake. A great deal of the water which went to make the mud that overwhelmed Wairoa may have been carried into the air as spray by the powerful steam jets that played through the lake. At any rate, a considerable quantity of water must have been carried up in this way.

An interesting question is: What is the nett result of the eruption in the nether regions? Has a cavernous space been formed by the removal of so much solid material? I think not.

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I think that by the expansion of unremoved rock by heat, and still more by its expansion by escape from the elastic compression it was previously subjected to, the place of the rock removed has been occupied. Were it not so, the extensive fissurings that have occurred in the bed of Rotomahana must have allowed the whole of its waters to sink into the cavity on the subsidence of the grand eruption. Possibly there has been some slight sinking of the ground immediately above the locality whence the rock was removed, (I have read something about the southern end of Lake Tarawera having subsided 18 inches), but the other means of filling the gap may have been sufficient for the purpose at present. As the heated rock cools and contracts further sinkage must occur, of which the deepening the existing lakes would be one indication. The second set of eruptions has been spoken of as hydrothermal, as distinguished from volcanic. I confess I do not understand the distinction—that is, if by the second eruption so much solid matter was ejected as I understand there was. It would seem to be a proper distinction to call that action hydrothermal which seemed to arise from access of water to heated beds; but, (as contended above), no considerable eruption could be originated in this way. There could be no solid ejections worth speaking of. For true volcanic action the water must be in the rock when heated, or, must have time to permeate a heated rock before a fissure of escape is provided, when the same results would follow. Yet it must be more difficult for steam to break up a solid rock, than one that from the effects of recent mechanical action upon it has lost much of its cohesion.

It has been remarked that there were no “warnings” of the eruption. There never are other warnings of a new outbreak than such as were given to those living in the neighbourhood. There were numerous earthquakes which indicated that movements were going on below. The springs were affected, being more copious, without meteorological cause, indicating that the movements were compressive—the water being squeezed out of the fissures in the strata. But it was impossible to gauge the extent of those movements, or foresee their actual effect.

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Art. XLIV.Observations on the Eruption of Mount Tarawera, Bay of Plenty, New Zealand, 10th June, 1886.

[Read before the Auckland Institute, 10th July, 1886.]

The 10th of June, 1886, is likely ever to be remembered in the history of New Zealand as that on which the colonists first had practically brought home to them the fact that the volcanic forces for which these islands are so celebrated had still an amount of vitality in them that was unlooked for and unexpected. The eruption of Tarawera Mountain, and the conversion of Rotomahana Lake into a crater, on that date, at about 2.15 a.m. has caused widespread consternation, the loss of several lives, and a feeling of anxiety as to whether this outburst will be confined to the immediate district where it occurred, or whether it will spread to others in which the signs of thermal action have been known for long periods.

Description of Volcanic District.

The volcanic districts of the North Island have been correctly described by Hochstetter as occupying three zones: the first, as that from Tongariro to White Island; the second, as that of the Isthmus of Auckland; the third, as that of the Bay of Islands.

There are many very essential differences in the general character of the results of volcanic action in these three zones, the first-named being that in which any extent of vitality appears to have remained unto the present day; though the Bay of Islands District has still its group of hot springs, whilst that of Auckland, so intimately known to all of us, has ceased to show any sign of life at all, though exhibiting to the observer some of the most perfect examples of extinct volcanic action in its several stages known to the world. Of these essential differences, the most prominent, and those which alone require notice on the present occasion, are the characters of the rockmasses and materials which go to build up the vast accumulation of volcanic remains forming the mountains and ejected matter in the different districts. The rocks of the central or Taupo zone are composed of materials known generally under the name of “acidic” rocks, whilst those of the other two zones are—in their latest manifestation, at all events—entirely formed of basic rocks. We may take, as general names descriptive of these two classes, trachytic rocks for the acidic areas, basaltic rocks for those of the basic areas, the distinction being in the nature of the constituents and their forms of aggregation.

The researches of modern science tend to confirm the idea that there is a regular sequence in the order in which these two

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classes of rocks are ejected from volcanoes—the acidic, or trachytic, denoting the earlier; the basic, or basaltic, the later stages of volcanic life. There are well-known exceptions to this general rule, but, taken as a whole, the evidence tends to show that such is the life history of most volcanic districts.

It may be that some volcanoes commence their career by the ejection of acidic matter, and continue throughout the whole course up to their final extinction, terminating in the ejection of basaltic matter, without material interruption of their activity—whilst others, after making a commencement, are quiescent, or only partially active, for ages, remaining in the acidic stages for such lengthened periods, that volcanoes which can be shown to be far younger in actual age have had their day and become extinct.

Such seems to be the case with the Taupo, or central zone. It is still in the acidic stage, whilst the younger volcanoes of this isthmus appear to have run their full course, and have become extinct.

In connection with this subject and the recent eruptions, (which may happen to mark the beginning of a period of greater activity), it is a matter of very great interest to ascertain whether they show by their action any change in the character of the ejected matter—whether, in fact, the ejecta are still acidic or trachytic, or whether, on the other hand, any basaltic or basic matter has also accompanied the outburst. We shall have something to say on this point further on.

The central volcanic district of this island is of immense extent, far larger, indeed, than is generally known, if we include in it the areas covered by volcanic matter, which spreads over a vast extent of country. Commencing in the far south, the noble mountain of Ruapehu, 8,878 feet high, which until quite recently was believed to be extinct, marks by its lava and consolidated mud streams the most southerly edge of the district. A line drawn thence in a north-east direction will pass along a belt of country celebrated all over the world for its extraordinary development of volcanic and thermal action, until it terminates in the active volcano of White Island. In this belt of country we have types of all the known forms of volcanic action. The active crater on Ngauruhoe has, within quite a recent period, (1869, and possibly 1881), ejected hot lavas, which were seen rolling down its symmetrical cone; whilst it still constantly emits clouds of steam from the solfataras at the bottom. Tongariro, a few miles north, is still active, but in the solfatara or fumarole stage. This fine mountain, 6,400 feet high, is now but the ruin of what it must have been in former times. Its seven craters, two of which have lakelets within them, and one with steam issuing from a fissure in its side, the powerful emission of steam from Ketetahi and Te Maari—points on its

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flanks—and the strong sulphurous stream flowing from the former, all show that the subterranean forces are still powerful. One of its craters contains a most beautiful and instructive example of a lava stream, whlch has flowed from the crater wall across the floor, spreading out in fan-shaped form, and having such a look of freshness about it that it is difficult to believe it is not still flowing.

A few miles to the north we find, at the southern end of Lake Taupo, a large number of hot and boiling springs, geysers, solfataras, and mud volcanoes, all in a very active state; whilst close by are the innumerable fumaroles of Waihi, and, but a short distance away, the group of hot springs recently reported by Mr. Laurence Cussen, which are quite new to Europeans. These are situated in a recess in the Kakaramea Mountain.

Stretching along a narrow belt of country from the north end of Taupo, still in the north-east direction, we find the vast number of hot springs, fumaroles, and geysers of Tapuaeharuru, Wairakei, Ohani, and Orakeikorako, with the extinct volcano of Tauhara, on which is an old crater, now almost hidden by a growth of tall forest trees. Orakeikorako, on the Waikato River, a place seldom visited by travellers, has a very large number of hot springs, some of which are forming terraces, but greatly inferior in their present aspect to those of Rotomahana. A little further in the same line northwards rises the Paeroa Range, the wall-like western face of which is covered at its base with boiling springs and mud volcanoes, which in one part (Kopiha) occupy the face of the hill from top to bottom, and the steam from which appears to have boiled the solid rock materials into a mass of clay of various colours. It is this part that Hochstetter refers to in his work, where he points out the possibility of the clays becoming so loosened, by the thermal action, that the whole hillside may some time collapse and deluge the Ratoreka Plain below.

On the northern slope of Paeroa are more hot springs, and then rises the mountain Maungaongaonga, evidently an old volcanic hill, though the crater is almost lost to view; and immediately to the east of it is Kakaramea, or Maungakakaramea, of which we have heard so much lately. It is an isolated conical hill, of considerable height, whose sides are seamed by gorges, the sites of former hot springs, and on the surface of which steam still escapes in a number of places, the ground occasionally being so hot as to be unpleasant to walk over. On its southern base, and extending thence to the head of the Waiotapu River—an affluent of the Waikato—are found a large number of hot springs, fumaroles, and mud volcanoes, with some terraces in course of formation, but which, however, cannot be at all compared to Rotomahana for beauty. Two

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little lakes, one of the most lovely blue colour, are also seen here, both of which have been the scene of active hot springs in the past.

We now come, by following in the same direction, to Okaro Lake, situated on the northern base of Kakaramea, and approach the country which is the scene of the late eruption. Passing this over for the moment, merely noting that Rotomahana is directly in the same line of country, we find the Tarawera, Ruawahia, and Wahanga Mountains, all formed of solid trachytic and rhyolitic rocks, and at their northern base come to the hot springs of the Tarawera River, which are continued down its course at intervals for several miles. This part of the volcanic belt is also marked by the old extinct volcano of Mount Edgcumbe, with its double crater and the hot springs. Near Te Teko we find, in Whale Island, situated 6 or 7 miles off Whakatane, another group of hot springs, and close to them the signs of former thermal action on Rurima Rocks, which have been described by Major Mair in vol. v., page 151, of the “Trans. N.Z. Inst.”; and, lastly, marking the most northerly point of activity, White Island, an active volcano, but now in the solfatara stage.

A glance at the map will show that the points of activity just described follow a fairly straight direction—north-east and south-west—and evidently mark a line of weakness in the Earth's crust, where the heated interior most readily finds a communication with the surface. But, in addition to this line, there are numerous other places on its flanks where hot springs and other indications of activity are found, as at Te Niho-o-te-Kiore on the Waikato, Rotorua, Rotoiti, Rotoma, Rotoehu, Maketu, and Mayor Island, all within a few miles of this central line.

Besides the places where these indications of volcanic action are present in a state of activity, we find that the whole country, for many miles on both sides, is composed of materials which owe their origin to volcanic action. Vast lava streams and sheets are visible, either as forming the hills or lying hidden under immense deposits of pumice, as on the Kaingaroa Plains, which are nearly everywhere underlain by a sheet of lava, or its accompanying mass of tufaceous rock derived from the same source. Isolated hills, built up of trachytic and rhyolitic rocks, denoting old volcanic necks, are common everywhere. The pumice which has been ejected by the ancient volcanoes covers an enormous extent of country, stretching north-easterly from Ruapehu to near Gisborne, where it is found as a thick layer on tops of the highest hills; and to the westwards, following the river valleys for many miles. We know that the plains of the Waikato are formed almost entirely of fine pumice-sand brought down from the central area, either by rivers or by the wind, or

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both, and that it has even been carried to within a few miles of New Plymouth. Volcanic mud is of common occurrence all over this country, but now so altered in appearance by decomposition as to be difficult of recognition, were it not for the underlying strata of pumice. It will be seen later on that the recent deposit of mud in the neighbourhood of Wairoa throws a good deal of light on the method of deposition of these beds of mud.

The changes in the central zone of volcanic action since this vast mass of ejecta was scattered all over the country have been, doubtless, very great. It is difficult to believe that all this material has issued from the extinct volcanoes, the remains of which we now see. It is far more reasonable to suppose that, during the ages which have passed since the later Eocene period, other volcanic vents have existed, and added to the immense mass of remains now visible, and that they themselves have disappeared, or been covered up by subsequent outbursts of the present volcanoes. We cannot assign, for instance, to the action of Ruapehu and Tongariro the cliffs of pure pumice on the east of Taupo, which are 400 feet high, nor have the vast lava flöes of the west side of the lake come from those same sources. Is it not far more reasonable to suppose that we now see in this long belt of country a great depression, due to the sinking of the whole surface, which carried with it the numbers of points of eruptions whose remains are now all that is left to denote their whereabouts? But to follow out this line of reasoning, and show from the evidence obtainable that this is probable, would occupy more time than is allowable. If this slight notice of some of the principal features of this great volcanic area has shown that changes have occurred in the past on a stupendous scale, it will prepare us for the acceptance of the idea that similar changes may always occur in that locality, and of this we have had recent evidence in the outburst at Tarawera.

Premonitory Signs.

New Zealand has been colonized so short a time, compared with the geologic ages of the past, that observation has not yet been continued sufficiently long to record any great changes in the volcanic region alluded to.

It is true that, from time to time, slight eruptions of Tongariro, (or rather Ngauruhoe), have been noted; earthquakes have occurred on a larger or smaller scale; the hot springs have been occasionally more or less active; floods and landslips, involving loss of life, and due more or less directly to volcanic agency, have occurred; but no great catastrophe has been recorded, to bring home to us the fact that any great changes are going on. But, nevertheless, a general opinion has been current to the

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effect that the forces have been decreasing in activity, rather than the contrary, and Maori tradition lends weight to this impression. They have many stories of the greater activity of the hot springs; indeed, Europeans have seen many fine geysers in play which are now quiet or extinct: but none of their legends speak of any great calamity having befallen their ancestors through volcanic agency, and we may be sure that amongst a people who are so scrupulously careful in handing down their history, any great catastrophe would have certainly been noted. A consideration of some few occurrences in that district during the twelve months, and immediately preceding the eruption, ought at least to have warned us that some changes were impending, a few of which will be noted.

On the 22nd November, 1885, Mr. Josiah Martin, F.G.S., who was then staying at Rotomahana, was lucky enough to witness what may be called an eruption of the basin on top of the White Terraces, a brief description of which he has been good enough to supply us with:—

“Nov. 19 to 21, 1885.—Wind, W., W.S.W. Rain and squalls. Bar. falling.

“Activity of geyser, normal; overflowing and covering the whole of the Terrace.

“Nov. 22.—Wind, S. Clear sky. Bar. rising.

“Visiting the Terrace at daybreak, I found that overflow had ceased, and water was rapidly retiring. At 6 a.m. the great cauldron was empty, and until noon it remained quiet, when activity was resumed by water rising slowly and filling the geyser tube. Very little increase in activity was noticed until 4 o'clock, when furious ebullition commenced, the water rising in wave-like upheavals, with occasional geyser fountains reaching a height of from 50 to 60 feet. By 5 o'clock the basin was half full, and violently agitated. Watching the activity from the upper platform of the Terrace, I was startled by a severe shock, with a deep boom like an underground explosion, when the water in the basin was instantly uplifted into an enormous dome, from the top of which an enormous column of water was projected vertically, with incredible velocity, falling again over the upper Terrace in a heavy shower.

“(The Natives encamped at the foot of Terrace were alarmed at this sudden eruption, which they said was the most violent they had ever seen.)

“By 6 o'clock the crater was full, and no further change was noticed until 8 o'clock, when the water began slowly to retire. On the following morning (23rd) the water was retiring, and by 9 a.m. the basin was left quite empty and dry. No action was noticed until evening, when the water rose a few feet within the basin.

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“On the morning of the 24th, the geyser very suddenly resumed its activity, several eruptive explosions following in rapid succession. On two occasions the column of water ejected must have reached a greater altitude than 150 feet, dense ascending clouds of steam accompanying every discharge, and rising to a height of 800 to 1,000 feet before being broken by the wind.

“On Nov. 22nd the movement of the aneroid exhibited a downward tendency, which commenced with the return of activity in the geyser, and continued during its excessive action. During the evening, as the geyser activity ceased, the opposite movement of the barometer was observed. But on three following days a recurrence of similar periods of activity in the geyser was accompanied by reversed conditions of barometric pressure.”

A paper which will be read before this Institute by Mr. Laurence Cussen at its next meeting will describe in some detail the crater on top of Ruapehu, which until quite recently was supposed to be extinct. We learn, however, from that gentleman that the crateral lake is filled with hot water, and that on the 16th April and 23rd May last he observed columns of steam rising as much as 300 feet above the mountain; and as nothing of the kind has ever been noticed before, it is a fair inference that the volcanic forces were in a state of greater activity than usual.

Mr. Dunnage, a young officer of the Survey Department, who performed the difficult feat of ascending Ruapehu so lately as the 8th of June last—almost mid-winter, in fact—reports: “The snow was in a favourable condition for climbing, but it was necessary to cut each footstep for the last thousand feet. Large quantities of steam were issuing from the little lake in the centre of the crater, nearly 1,000 feet below us, but was all condensed before reaching the top of the crater. The cold was very severe.”

About a fortnight previous to the eruption, one of the fumaroles at Tokaanu, at the south end of Lake Taupo, suddenly burst forth, throwing up showers of mud for several yards round; but it had returned to its usual state on or about the 10th June.

Major Scannell is good enough to inform us that some little time previously to the eruption, a new hot spring broke out at Wairakei, near the north end of Taupo.

About a week prior to the eruption, a wave was noted on Lake Tarawera, causing the waters to rise about 2 feet above the ordinary level, which broke on the shores, washing the boats out of the sheds, and causing some alarm to the Maoris, who, apparently, had never witnessed anything of the kind before. At the same date, some visitors to Rotomahana found

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that the Pink Terrace had been in eruption, throwing out mud for several yards round, an occurrence which has never been noted before.

It will be remembered that on the evening previous to the eruption an occultation of Mars by the Moon occurred, at 10.20 p.m., the moon being just then entering her second quarter. It would be high water on the coast near Maketu that evening at about 10 p.m. We do not give much importance to these facts, but it is worthy of note that the well-known theory of the tides assumes that the waters of the ocean are at high water piled up, as it were, on that particular portion of the earth's surface which is just under the moon; but through friction, and the counter attraction of the sun, that the tidal-wave lags after the time of passing of the moon over any particular meridian. It is equally a part of this theory that the solid materials of the earth are at the same moment subject to a wave—much more limited in extent, but still appreciable; and it is well known that an atmospheric wave passes round the earth at 2 o'clock each day. Hence, the crust of the earth being in a state of tension, if there is any predisposing cause tending to a fracture about the period of this earth-wave, it is a natural inference that the conditions are then most favourable for the production of such fractures. The attraction of the planet Mars, added to that of the Moon, may be and doubtless is, very slight; but the fact remains that, whatever influence the moon may exert at any particular moment, it happened to be greater, by the sum of her own and that of the planet, very shortly before the eruption.

The state of the barometer, as recorded by the self-registering instrument at Rotorua, does not indicate any abnormal depression, either shortly before or during the catastrophe. It is found that on Tuesday, the

8th,at noon, thereading was 29.40,erduced to sea-line, 30.20
8th " midnight " 29.28 " 30.08
9th " 6 a.m. " 29.23 " 30.03
9th " 10 " 29.17 " 29.97
9th " noon " 29.12 " 29.90
9th " 6 p.m. " 29.00 " 29.80
9th " midnight " 29.30 " 30.01
10th " 2 a.m. " 29.30 " 30.01
Eruption.
10th " 4 a.m. " 29.40 " 30.20
10th " 6 a.m. " 29.50 " 30.30
10th " noon " 29.50 " 30.30

from which time it altered little for the next two days. It will be seen that there was a somewhat sudden fall a little before noon on the Tuesday, but still nothing extraordinary, or such as we learn has occurred at other great outbursts in other parts of the world.

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Approaching, now, to the date of the eruption, we find that there was a heavy rain for the great part of the 9th June, which cleared up towards evening. The wind on the night of the 9th was southerly, changing during the eruption to the south-west, from which direction it blew hard until 4 a.m., when it dropped. At Auckland, Gisborne, Waikato, and Lichfield the wind was south-west. Major Scannell, who saw the outburst from Taupo, says that when he first beheld the cloud of ashes, it was moving south and east, but a sharp south wind sprang up about 3 o'clock and carried the cloud westward and northward.

Phenomena observed at the Outburst.

The amount of information which has been recorded as to the actxsual outburst is very considerable, but all through there appears to be a want of exactness as to the times and order of occurrence of the phenomena observed, a very natural result of the excitement and confusion into which people would be thrown by occurrences which threatened their very existence. But the best accounts obtainable seem to place the first signs of anything extraordinary happening, at about 1 a.m. on the 10th June, 1886, when slight earthquake shocks were felt by the people at Wairoa, and at Rotorua, (accompanied at the latter place by rumbling noises), which appear to have been continued as earth-tremors till 2 a.m., or past. At 2.10 or 2.20 the rumbling noise had become a continuous and fearful roar, accompanied by a heavy shock of earthquake; and at this same time, or immediately afterwards, an enormous cloud of smoke and vapour was observed from Wairoa, rising over the hills which shut in that village from a clear view towards Tarawera Mountain, the outside edges and fringes of the different masses of which were outlined by vivid flashes of electricity, darting through the cloud and colouring it most brilliantly and beautifully. This electric display was accompanied by a rustling or crackling noise, which appears to have been heard above the deafening roar, and which is probably the same noise as is heard in electric discharges of an artificial kind, and also probably the same as is heard sometimes at great auroral displays. This heavy shock of earthquake is doubtless the same as that reported at Maketu at 2.30, Tauranga 2 a.m., and Makarewarewa at 2.30. It was noted by two observers, (Messrs. Blythe and Greenlees), that from 2.30 onwards severe shocks occurred at regular ten-minutes' intervals up to 3.30. The latter gentleman had the presence of mind to observe, from the swinging of a ham, that the shocks came from the direction of Tarawera. It is probable that the eruption of Tarawera first took place in any strength at about 1.45 a.m. As described by Mr. McRae, who saw it from the old Mission Station, soon after the outburst, three columns of fire and flame (or probably the glare

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reflected on the vapour from lava below) were shooting upward from the flat plateau-like summit of the mountain to an immense height, with flashes of electricity darting forth in all directions, accompanied by balls of fire, some of which fell at great distances, indeed as far off as the Wairoa village, some 8 miles from the seat of eruption. Small stones now began to fall, as the great black cloud which had formed over the mountain worked towards the west, to be quickly followed by a downpour of mud and water and heavy stones, which battered down many of the houses in the village. The mud appears to have fallen in the form of an exceedingly heavy rain, with sometimes large lumps of mud, and this continued up till 6 a.m. All this time, there appears to have been a more or less strong odour of sulphur experienced by the people at Wairoa; and Mr. Blythe describes a hot suffocating blast, which nearly choked himself and Miss Hasard, after their escape from the burning house, and which warmed them through.

Soon after the first outburst, and before the fall of the first stones, a great wind arose, which rushed in the direction of the point of eruption with great force, and was most bitterly cold. It is noticeable that the people who survived, and were nearest to the seat of the eruption, viz., those at the Wairoa, failed to hear the loud detonations which reached Auckland and other places. Probably the loud and continuous roar drowned the louder reports.

These explosions were heard at Hamilton, Cambridge, Lichfield, Coromandel, Te Aroha, Wanganui, Tauranga, Maketu, Taupo, Christchurch, Wellington, Nelson, Blenheim, Whakatane, Opotiki, Auckland, New Plymouth, Whangarei, and Helensville, and sounded like the reports of distant cannon, or—as has been described by a large number of people from different places—like some one banging an iron tank. The flashes of the electric display were distinctly seen here in Auckland, a distance of 120 miles in a straight line from Tarawera. The immense cloud of ashes, mud, and sand which was shot high up into the air darkened the sky till long after daylight should have appeared. It is stated that it was quite dark at Rotorua till 7.30, (the ashes commenced falling there at 4 a.m.), and again at 9 a.m.; at Opotiki till 10 a.m., at Tauranga till 9 a.m.; at Te Puke it is said to have been dark as late as 2 p.m. on the 10th; at Maketu till 10 a.m.; the ashes beginning to fall there at 5.30 a.m. The height to which the mass of light ashes was ejected must have been enormous. Professor Verbeek, who was appointed by the Dutch Government to report on and describe the eruption of Krakatoa in May and August, 1883, states that the column of steam arose from that eruption to a height of 50,000 feet, or over 9 miles. The dark cloud of dust and ashes from Tarawera must have been nearly as high as this column of

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steam. Mr. R. Arthur, of Mount Eden, who had a distinct view of the cloud illumined by electric flashes on the morning of the 10th, took notice of the height which it appeared as seen behind One Tree Hill; and the angle of elevation, as afterwards measured by Mr. Vickerman, of the Survey Department, gives a height, as computed by him, of 44,700 feet above Ruawahia, or a little over 8 miles. Although this method of observation is not a very accurate one, and may not be quite correct, it gives some approximation to the height.* We know from actual measurement that the column of steam arising from Rotomahana several days after the eruption was 15,400 feet, and even then the top of the column could not be seen, from its proximity to the observer. The ashes and dust ejected fell on the coast line at points 160 miles apart in a straight line—viz., at Tairua and at Anaura, a few miles north of Gisborne, and some of it fell on the s.s. “Southern Cross” off the East Cape, and on the s.s. “Wellington” near Mayor Island. It thus covered an area of land equal to 5,700 square miles with more or less of the deposit; on the edges of which, of course, it is barely visible.

In thus calling attention to the great height to which the dust and ashes were projected by the explosive force of the steam, a distinction must be drawn between this height and that mentioned by Professor Verbeek. In the Tarawera case this refers to the top of the cloud of ashes; in that of Krakatoa to the column of steam seen long after the eruption. Nor must it be inferred that in the New Zealand eruption we shall necessarily see the same extraordinary and beautiful atmospheric effects which followed the Sunda eruption.

The electric phenomena accompanying the outburst must have been on the grandest scale. The vast cloud appears to have been highly charged with lightning, which was flashing and darting across and through it: sometimes shooting upwards in long curved streamers, at others following horizontal or downward directions, the flashes frequently ending in balls of fire, which as often burst into thousands of rocket-like stars. Fire-balls fell at the Wairoa and other places, and doubtless the fires which occurred at Mr. Hazard's house and in the forest near Lake Tarawera were due to these.

Earthquakes.

The earthquakes appear to have been almost continuous from 1 a.m. to 3.30 a.m., with heavier shocks at about 4.30 and about 5.30, which were felt over a large district, extending in an east and west direction from Te Aroha, where they were slight, to Opotiki, where 71 separate shocks were felt; and in a north and south direction from the coast to Taupo. Although

[Footnote] * Archdeacon Williams, of Gisborne, who saw the flashes of lightning on the 10th, calculates that they were seen at an elevation of 6 miles.

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described as severe, (as they no doubt appeared to those who experienced them), they cannot really be so classed when it is taken into consideration that no chimneys fell, nor were light articles, such as bottles, vases, etc., cast down from shelves, except in one or two instances. No one who experienced the heavy earthquakes of 1848 or 1855, which caused such dismay in the vicinity of Cook Strait, could call those recently occurring severe ones.

It is true, in some places the earth has cracked and opened, but nowhere to any great extent. Nothing occurred like the great cracks at Wanganui and Wairau, in Cook Strait.

It is a very noticeable fact that all of the cracks we saw took the general north-easterly direction of the line of volcanic action, and all of them followed closely along depressions in the surface, which are undoubtedly old cracks, due to much heavier earthquakes in the past.

Sympathetic Action of other points.

It has been stated that the eruption is quite local in its action, and goes to prove that the series of hot springs in different places, and other signs of volcanic action in the central zone, are separated, and have no connection or sympathy with one or another. A consideration of the following facts relating to events which occurred at the time of eruption, or soon after, go to prove that such a conclusion has been drawn from insufficient data.

The hot springs in the neighbourhood of Rotorua were greatly affected. A small steam fumarole, (which in its ordinary state was only occasionally visible), near the Government Agent's house, became a large boiling spring about 10 feet in diameter, from which a good-sized stream of hot water ran away towards the lake. Further north—at the base of the Pukeroa hill, and in the direction of the Maori village of Ohinemutu—steam came forth from innumerable cracks in the earth, sometimes accompanied by hot water, which formed streams running alongside the road from the old to the new township; and in the pah itself a spring burst out in the great meeting-house of Tamate Kapua; another in the path leading down to it; and yet another just behind the building. All of these outbursts occurred on the night of the eruption; they all follow, however, the old deposits of sinter at the base of the Pukeroa hill—the last remaining signs of former great activity in that locality. The activity of the vast number of fumaroles and springs in and around Ohinemutu was certainly greater than usual a few days after the 10th. The level of Lake Rotorua oscillated somewhat on the 10th June, but to no great extent. At 7 a.m. it fell 1 inch, at 9 a.m. it rose 6 inches, and fell again

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at noon 3 inches, and remained so all day, falling on the night of the 10th 5 inches; since when the oscillation has been continuous, but to no very great extent. The temperature of Rachel's Spring at the Sanatorium on the 11th June was 170°, and from that date to 1st July it gradually rose to 196°, with a greater flow than before. For these exact data we are indebted to Mr. Boscawen, who obtained them from Mr. Hall, the Observer.

In the far north of the central zone, at White Island, it was reported by the s.s. “Jane Douglas” that the crater was showing unusual signs of activity at 9 p.m. on the 13th, whilst the “Hinemoa” reported it to be in its usual state on the 14th. Te Puke settlers saw a “violent eruption of steam on the morning of the 10th.” The “Te Anau” reported that nothing but an unusual amount of steam was rising on the 13th. On the 14th, vast columns of steam were reported as being seen all day from Tauranga, and the same on the 15th. At Wairakei, near Taupo, the springs and geysers are reported to be “in an extraordinary state of activity” on the 10th. We may add that we saw much more steam than usual arising from the large group of springs south of Maungakakaramea on the 14th; but these being in the direct line of the great fissure, it is only natural to expect this.

Taken altogether, then, this group of authenticated facts goes to prove that the disturbance was felt all along the central line of activity of the central zone, from extreme north to south, as well as on its flanks.

Description of the Points of Eruption

We will commence our description of the effects of the eruption, as seen by ourselves on the 13th, 14th, 15th, 16th of June, by commencing at the southern end, near Lake Okaro, and tracing it thence northwards to the Wahanga Mountain, the most northerly point of eruption. This line, or irregular (and sometimes hidden) fissure, is about 8 ½ miles long, running in a general north-easterly direction, and along it can be traced a series of craters and points of eruption almost, though not quite, continuous.

Appearance of the District, approaching from the South

Emerging from the bush called Pareheru, which the track approaching Rotomahana traverses, the scene is wonderfully striking. The whole country is clothed in a pale grey mantle. Hill and dale, level and steep, all is of the same hue. In the far distance, as in the near foreground, nothing has escaped this ashen covering save the Okaro Lake, which lies before us

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sombre, silent, and unruffled. Away in the front rises an ever rolling, slow-changing, towering mass of steam, interspersed in the lower portions with sudden bursts of darker material, which prove to be stones, sand, mud, and water, flung up to the height of 400 or 500 feet above the lip of the crater. At times, the bright sun glancing over this wondrous column gives a vivid brightness to it; and again, so brilliantly reflected is the sunlight from the more distant portions of the mantled earth, as to bring vividly to the mind of the onlooker the semblance of a vast field of snow.

On entering this sombre plain, the ashen covering proves to be a fine, dry, powdered material, having throughout small fragments of scoria. Occasionally spherical or ovoid nodules are found, which easily crush between the fingers, and sometimes contain a nucleus in the shape of a rounded fragment of scoria.

Advancing through this material—which closely resembles in colour and appearance Portland cement—the deposit becomes deeper, so that walking was very fatiguing. In many parts each step was knee-deep, while, by leaving the ridges, the soft ash was found to be so deep as to be dangerous, and the effects of the wind stirring the surface made breathing laboured.

Travelling somewhat to the north of Okaro Lake for the distance of about a mile and a half, brought us to the most southern part of the fissure, which has extended from the Rotomakariri Lake in the direction of the Okaro Lake, partly through the Haumi Stream. On the line of the fissure in this direction are five distinct craters, the most northerly of which was decidedly the most active, while the southerly one was nearly dormant.

On reaching the edge of this one, which was ovoid in shape, the bottom was found to be covered with muddy water, evidently hot and probably deep. In the northern part of the crater an occasional uprush of water would take place, rising about 20 feet in height, and slowly falling back into the pool. This would cause a wave to gradually extend, which, reaching the sides, would wash in some of the steep sloping earth, followed occasionally by heavy slips extending to the surface. (Since our visit, Mr. Boscawen and Mr. Main have seen these craters, and have each witnessed the most southern crater, which we have stated as dormant, suddenly, and without warning, send masses of water, mud, and stones high into the air above the edge of the crater, after which, Mr. Main asserts, the activity would be followed by each of the others in succession to the northwards.) At the lip of the crater, and for a considerable distance back from the edge, cracks had formed following the contour of the lip, and from 2 to 6 or 7 feet apart. These cracks made travelling dangerous in the near vicinity of the craters, as the

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occasional shocks of earthquake were liable to precipitate the overhanging portions to the bottom. The depth from the lip to the water was estimated at about 350 feet, and the length about 200 yards, with a width at the lips of 100 yards.

The second crater to the north was rather more active, sending up columns of steam, through which occasionally an uprush of stones and mud was discernible. Owing to a heavy slip of earth into this crater, a terrace had been formed about 50 feet below the lip, and with a little effort it was possible to obtain an excellent view from this place, not only of the crater in question, but of the steam-jets in the third crater. (The second and third craters here referred to subsequently became joined in one, called “Echo Lake Crater.”) These, to the number of five, rose in unbroken columns to the height of about 40 feet, sending up stones in large numbers, some of which reached above the surface. The roar of the escaping steam from this crater was very great. Passing round to the north, it was possible to cross the line by a narrow passage between the third and fourth craters; and from this point an excellent view could be obtained of the energy displayed by the escaping steam, which sent up showers of stones to within a few feet of us.

Looking north from the passage on which we stood, the fourth crater (since called the “Inferno”) displayed a very peculiar form. It had the appearance of an immense cutting through a long hill, and this was actually the method of its formation: the disruptive force having been exerted under the centre of a long spur, had removed the centre of the hill throughout its entire length, and deposited portions of the material on its sides. It was noticeable that in each of the craters already described, the forces had been exerted in the same manner, the crater having been formed in a hill, the material of which had been ejected to a considerable distance on each side. In the most southerly crater the formation was most distinctly shown, as the surface soil was marked by a ragged fringe of dead fern and ti-tree, which extended all round the side from about 10 to 25 feet below the lip of the crater, the ejected material taking the usual outward slope characteristic of volcanic cones. The natural contour of all the land covered in this vicinity, notwithstanding the tremendous forces which had been at work, was very little altered, and in one instance, on a steep slope which faced the westward, the fern and ti-tree was still visible. Still proceeding to the north, the fifth or Black Crater was reached, and this was certainly the most active in the line. After a toilsome ascent, a position was obtained from which the activity could be witnessed with comparative safety. This cone was the highest of all, and far above the level of its edges were thrown immense quantities of stones, mud, and water, the majority of which fell back

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into the crater, though large masses were flung with a terrible clatter on to the sides, gradually building them to a greater height. Some of the stones launched out fell several hundred yards from the edge, burying themselves in the mud, and sending up volumes of steam. It was now possible to witness the manner in which the stones were buried, both in the mud and in the dry deposit, and to note how greatly reduced was the activity of the geyser action to what its earlier efforts had been.

While traversing the ground between the edge of the deposit and the craters, a large number of circular depressions had been observed, of various sizes, and having the appearance of fumaroles. Some of these were not less than half a mile from the edge of the nearest crater, while as the distance was reduced the number of these holes increased. Finding a place where water and mud had been ejected in sufficient quantity to form a moderate hardness on the surface of the dry deposit, a search was made at the bottom of some of the holes, resulting, after a little excavation, in each case in finding a large stone. Sometimes these had only just penetrated the hard wet crust, and at others had disappeared in the dry deposit which lay below. In one small valley, where an immense deposit of stones had taken place, a rhomboid had been thrown which measured about 4 ft. by 2 ft. 6 in.* This had a raised mass of material round it, showing that it had been thrown, and had not rolled to its situation. During the whole of the time spent on the sides of this crater, a constant tremor of the earth was noticeable, and a heavier discharge than usual of mud and stones was invariably accompanied by a shock, which gave timely warning before the effects were seen above the edge of the crater.

Skirting this active geyser, and ascending the hill called Hape-o-toroa, the former Rotomahana Lake lies before us, sending up a great volume of steam.

This hill, Te Hape-o-toroa, is situated immediately to the south of the Rotomahana crater, and, being the highest land anywhere in the neighbourhood, commands a fine view of all the points of eruption excepting Tarawera and Ruawahia, the flanks of which are occasionally visible through the vast mass of vapour ascending into the upper regions of the air. Its close proximity to the southern edge of the crater—being distant from it only 250 yards—enables the beholder to look down on to the various points of eruption with great advantage, though it must be acknowledged that the constant shocks of earthquake induce a wondering expectation as to whether the steep hillside will not be precipitated into the depths below. Immediately to the

[Footnote] * Subsequent explorations show that several rocks, measuring over 1,000 cubic feet in solid contents, have been ejected in this neighbourhood.

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right hand, and at the eastern base of the hill, is the course o the Haumi Stream, which formerly wound its way from Okaro Lake to Rotomahans, joining that lake a little to the south-east of the Pink Terraces. But what a change has occurred here! Directly at the base of the hill is a great fissure, from which issues an enormous mass of steam, whilst every now and then, after a loud report like a cannon shot, it is accompanied by large quantities of stones and sand, shooting up into the air and falling generally back again from whence they came. Immediately in front, between us and the crater lip, is a deep dark hole, sending forth a high column of steam. The edges of the crater are covered with fragments of stone ejected from it.

One looks in vain for any sign of the Pink Terrace: all view in that direction is cut off by the column of steam. The edge of Rotomahana Lake is now far within the crater wall, which follows round from our immediate front in a westerly, then north-westerly, northerly, and north-easterly direction to the site of the White Terrace. The crater has clearly eaten its way back from the edge of the lake, a distance of at least a quarter of a mile from the site of the Pink Terrace; and all along the foot of the wall the steam rises from so many points, that it is impossible for the eye to penetrate within its precincts, except on rare occasions when the wind causes a separation of the masses of vapour; and then is disclosed to view for a short time a cavernous-looking aperture, in which can be discerned a picture once seen never to be forgotten. A dismal coffee-coloured light, penetrating the vast mass of vapour from above, enables us indistinctly to see a horrible mass of seething, boiling waters, stained of a black or dirty brown colour, encircled by walls and hillocks of dreadful-looking hot mud, from which the steam curls up in innumerable places. Mud volcanoes scatter their contents around on all sides, whilst every now and then a loud detonation precedes the discharge of a column of water, mud, and stones high into the air, and as they fall splash the black mud right and left. The whole interior surface of the crater, as far as the eye can penetrate, seems to have been boiled and steamed and hurled about to such an extent that the old landmarks are no longer recognizable. Whilst the greatest activity seems to follow the foot of the crater-wall round by the western side, the eastern has also its points of eruption, from which vast columns of steam arise to join the general mass above; but, as yet, no one has been able to obtain a clear view of this eastern side. The size of this crateral hollow is about 1 ½ miles in a North and South direction, with a width of about 1¼ miles.

From a point which was reached with great difficulty on the west side of the crater, a view is obtained looking north-east, past the site of the White Terraces, and embracing the whole of

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Tarawera Mountain. The deep sand in this direction makes progression most slow and fatiguing, and not without danger from the slips of sand on the steep hill sides. We looked in vain for any sign of the White Terraces; and as the eye gradually got to recognize some of the more prominent features of the country near there, under their altered shapes and appearance, the conclusion was forced on us that these beautiful terraces—the most lovely and wonderful of their kind on the whole earth—had disappeared for ever from mortal view. The changes in the general appearance of the country near there are so great, that, even with a familiar knowledge of the locality, which had been impressed on the mind in a visit to the same spot on which we now stood only three short months before, we recognized with great difficulty and uncertainty the main features of the land. But, still, the evidence of the whole contour of the country goes to show that the site of the terraces is now occupied by a horseshoe-shaped recess or bay in the general line of the main crater, from which an enormous column of steam arises high into the air. Nearer to us than this recess could be seen a gentle declivity, forming a very shallow valley, in which once ran the Kaiwaka Stream, the former outlet to Lake Rotomahana. This once deep gully is now nearly filled to its top with ejected matter, to a depth of 80 feet, of stone, sand, and mud. All around this part of the crater edge the ground was cracked and fissured by earthquakes, and by the torrents of water ejected from the crater. Lying immediately to the west of it was a large deposit of mud, which extended some way up the range that divides Rotomahana from the Wairoa Stream, and on its surface were occasional pools of water, the remains of deluges cast out from the crater.

From this same spot a good view of the whole of the south end and top of Tarawera is obtained. The eye is immediately attracted by the altered appearance of the south-west end of the mountain. Here a great rift—an enormous chasm—extends from the plateau-like top to the base of the mountain, ending (apparently) quite close to the site of the former Rotomakariri Lake. Various estimates have been formed of the dimensions of this great rift, and we believe that we are quite within the mark in stating it to be over a mile long, 500 feet wide, and 500 feet deep. No one, up to the present time, has been able to see the actual bottom of it.* Out of this chasm rise, at several points, columns of dense black or brown smoke, not continuously, but intermittently; but no sign of any ejection of solid material was visible at the time. The edges were quite sharp and ragged,

[Footnote] * Subsequent exploration proves that this fissure extends right down to Rotomahana, a distance of over two miles; and within it, just at the foot of Tarawera, the new Lake Rotomakariri has been formed.

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as if the solid rock had been ripped open by the enormous force of imprisoned steam; and in its upper part the ashes, rocks, and the ground generally for a long distance on either side, were coloured a yellowish-green, due no doubt to some of the products of volcanic action—such as ferric chloride. The slopes of the mountain around were covered deeply by ashes and stones, and near the base of it steam escaped from several cracks. As we sat on the surface of the sand observing the chasm through the glass, frequent shocks of earthquake caused cracks to open near the rift, and steam was seen to escape in little jets, ceasing, however, soon afterwards, as the cracks closed in or the loose materials fell into and stopped the vents. The southern end of the rift seems to be continued as a hollow right into the site of Rotomakariri, which is now occupied by a crater, from which rises a vast column of steam and occasionally smoke; indeed, this part seems to be one of the most active craters of the whole series. Mr. Morgan, who approached this side of the crater from Galatea on the night of the 14th, states that he saw a great glare as of fire, and a large mass of smoke issuing therefrom.

During the time we were in the district the weather was most beautifully clear, with a light south-west wind; and this allowed of a careful study through the glass of the heights of Wahanga, Ruawahia, and Tarawera, as seen from various points. That great changes have taken place in the two latter is obvious to any one who knew their former shapes and appearance. In 1874 we made the ascent of Ruawahia on three occasions, starting from near the outlet of Lake Tarawera, and are thus able to give some description of the range prior to the eruption. All those who have visited the Lake District are familiar with this range, which rises out of the lake on its eastern shore by gradual easy slopes, until near the summit, where a wall-like mass of trachytic or rhyolitic rocks marks the division between its plateau-like top and the gentler slopes below. From the northern end of Wahanga to the southern end of Tarawera is a distance of about three miles, whilst the plateau has a width of perhaps a mile, broken at one mile from the north end by a deep saddle, dividing Wahanga from Ruawahia. The surface of the plateau was covered by immense masses of broken trachytic rocks, which looked as if they had been shivered and fractured by the action of the frost into long angular blocks of various sizes. Running in all directions were depressions or crevices dividing the surface into hummocks, and making travelling very difficult; whilst occasionally a hillock formed of the piled up masses of loose rock rose above the general surface. No sign of any crater was seen, though the rocks are all undoubtedly due to volcanic action. Possibly in this range we see an illustration of one of those great masses of ejected lava described by

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Judd, which, issuing from a vent or vents below in a viscid state, swell up in a somewhat rounded mass without forming a crater. Of this description is the well-known Grand Puy of Sarcouci, in France, and numbers of others in various parts of the world. The cracked and fissured surface of these mountains would then be accounted for by cooling from a state of considerable tension.

That a great change has taken place in the mountain top is obvious. The glass shows clearly that Ruawahia and Tarawera (both of these names being on the same plateau—the latter being the name of the southern end), have been apparently rent along their whole length, and some of the little peaks along this rent appear to be the result of solid materials ejected from below, and built up by stratified layers of scoria or stone having the outward dip common to volcanoes. Smoke was rising from several points for a distance of a mile and a half, but not in any great quantity, though occasionally it increased in volume, sending a dark black cloud high into the air. The surface of the ground on top was coloured a yellowish-green for many acres, denoting the presence probably of ferric chloride, whilst all the original fissures appeared to have been filled up to one general slope by the materials ejected. It is as yet premature to make any definite statement as to whether the mountain is higher than it formerly was—namely, 3,606 feet; but it certainly has that appearance, and the evidence of sketches and photographs tends in the same direction. We believe that when the mountain can be approached sufficiently near it will be found that a true crater has been formed on the north-east side of it.*

In general appearance Wahanga seems to have altered, but not to so great a degree as Ruawahia. Smoke issues in smaller quantities from several places on its summit, but principally from the highest point. It also is covered with a mantle of ashes and stone ejected from one of the vents.

Dr. Hector, in his report on the eruption, has given some slight weight to the significance of these three names as bearing on the question of former activity, of which, however, no tradition exists among the Maoris; but we think no value can be attached to this argument when it is known that each name has another interpretation; and we cannot think that the obvious

[Footnote] * The height of Ruawahia since obtained is 3,770 feet, showing an increase in height of about 170 feet. This is caused by the black and red vesicular scoria piled along the edges of the great fissure.

[Footnote] † The great fissure is found to extend along the eastern face of Wahanga nearly to its northern end, and in it are two deep craters, one of them being the deepest of any along the whole line.

[Footnote] ‡ “Preliminary Report on the Volcanic Eruptions at Tarawera on 10th June,” dated 23rd June. Appendix, Jour. H. of R., 1886.

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signs of great age in the trachytic lavas of which the mountains are formed will allow of our placing the time of its former (latest) activity within the historical or traditional period, a time extending back for not more than five hundred years.

Many will remember the fine forest that occupied the western slopes of Ruawahia, reaching down nearly to the lake margin. Nothing is left but a number of stumps and branchless trees, many of them burning, and adding by their weird appearance to the general desolate look of the country. The clumps of trees which adorned the south-eastern slope of Tarawera have almost wholly disappeared, being covered up by the deposits which buried the little Maori village in which poor Brown and his Maori friends lie buried. A few charred and blackened stumps are alone left to denote the spot.

The changes in the contour of the country around the base of Tarawera and Rotomahana are most remarkable, and bear witness to the vast amount of matter which has been ejected. Messrs. Harrow and Edwards, who formed part of the boating party which crossed Lake Tarawera to search for Te Ariki village, where it was known a large number of Maoris lay buried, tell us that in many places the shore of the lake near the old landing-place on the route to Rotomahana is so altered by the conversion of part of the lake into dry land that localities cannot be recognized. They furnish an instructive section of the ejecta, as seen in the bed of a torrent cut through it since the 10th June:—

Ft. in.
On the bottom were large stones 0 0
Ashes and mud 3 0
Scoriæ (still hot on the 15th) 1 0
Ashes and sand 15 0
Mud, forming the surface 4 0

This gives a depth of 23 feet in that particular locality, but it is evidently much deeper in others. On the slopes of Te Hape-o-toroa, we can state positively that in one place 25 feet of matter has been deposited, the topmost layers being fine and coarse sand mixed with small fragments of stone and sinter; and this deposit was quite hot on the sixth day after the eruption at a depth of 4 or 5 feet. The vast number of small fragments of siliceous sinter scattered over the country west and south-west of Rotomahana, points to the destruction of the terraces, of which materials they were mainly formed.

The Steam Cloud.

Riding home, weary and covered with mud, we halted to gaze upon one of the most glorious sights man could view. We stood in a light-timbered grove just outside the belt of the ashcovered

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plain, the setting sun at our back. Away and away in our front for miles lay the scene that not long since looked like snow, but now, reflected on it, the rays of the setting sun gave it the aspect of red coral. But, above all, there rose in solemn grandeur the towering mass of steam—thousands upon thousands of feet it ascended, until its crown was lost in the bright, fleecy clouds that came rolling up from the south. Bright, aye bright with the full effulgence of the orb which was still high above the horizon there; but lower, the dazzling brightness waned, and a faint glint of a golden hue was seen, to be rivalled by the richer colours and deeper gold of the nether parts until they deepened and sank through rose to carmine, and deeper hues suffused the base and the far-reaching crimson plain, while the deep greens of the bush in which we stood made up a picture difficult to equal, impossible to excel. And thus from earth to sky rolled the ever-changing mass of steam, rent at the base with the up-rush of countless geysers, imparting to it changing and varying tints, beautiful and transient; but above, calm, solemn, and gorgeous, and apparently immovable. Slowly the deeper tints crept up, and left the base white and beautiful in the light of the bright full moon, while the crown still reflected the deep soft tints of a sun which had long since set with us.

Appearance of the Road to the Wairoa.

The appearance of the district, after having entered upon that portion upon which the deposit of mud has fallen, is sombre in the extreme. The view all round is the same: the neutral grey of the wet mud is spread as a pall over the earth. The contour of the ground is not altered, only the steeper angles are rounded off, the smaller gullies and hollows filled up by the all-pervading mud. Locomotion is naturally retarded, the track having from 4 to 6 inches deep of the plastic mass. Proceeding in the direction of the Wairoa, we reach the Tikitapu Bush, so famed for its beauty of tree and fern. Now, all verdure is gone, trees and shrubs are alike stripped of their leaves, and the bark no longer shows its natural and varied hues, but is encased with the all-pervading grey. Only in some hollow of a larger tree on the sheltered side may be seen a few scattered leaves of some close-clinging creeper, or the hardy leaves of the tataramoa, bespattered with mud. Advancing into the bush, we soon came upon more striking effects than that wrought by the fall of the deposit. Trees are lying uprooted, increasing in number as we reach the Tikitapu Lake. Advancing along the road, we find them lying parallel with it in nearly every instance. It runs in a nearly straight line in a S.E. direction, bearing directly to Rotomahana. In one short stretch, near the lake, twenty trees were counted lying near to and on either side of the road, and in only one instance was it necessary to make a detour, on

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account of a tree which had fallen across the road. This remarkable effect of the storm was only noticeable in the bottom of the valley through which the road ran, as on either side on the hills the trees seemed to have been blown irregularly, and in different directions.

To account for the regular disposition of the trees is not difficult, when we remember that the evidence of the survivors at the Wairoa shows that during the precipitation of the mud a terrible storm was blowing in their direction, from the direction of the valleys which lead down to the village from S.E. of W. This wind would find its easiest passage through the bush up the road which ran in the same direction in which it was travelling, until the pressure became so great that the tall trees abutting on the road, being unable to bear it, were precipitated in the same plane. Further evidence as to this as a cause is the precipitation of the mud on the trunks of the trees still left standing, but only on the S.E. side; while what few leaves of creepers are still left clinging to the trees are only noticeable on the N.W.

Advancing towards the Rotokakahi Lake, the mud deposits on the hill sides appear to be more liquid, and have run together, giving the hills a striped appearance. The steeper angle, and rocky nature of the ground admitting less absorption of the watery matter, is no doubt the cause of this, and will have a serious effect in regard to the future stability of the deposit. In the valley of the Wairoa the deposit is much deeper, and where it has drifted up against fences or trees must be from 5 to 7 feet in depth. At the time of our visit, however, Mr. Macrae's waggon was being dug out from where it had been buried while standing on the road, and there the depth from the surface of the deposit to the top of the old road was 2ft. 8in. Through this deposit were mixed fragments and masses of rock, much of it being scoria; while in some of the roofs of the houses were clearly discernible the holes which had been caused by the force with which these stones had descended. In one instance, we removed a stone which was still imbedded in the hole it had produced. Here, again, the deposit piled on the sides of houses, fences, and trees showed that the material must have been carried with great force in a northerly direction. (On the edge of the deposit in the direction of Ohinemutu it was interesting to note the effect of the mud and stones which had been precipitated on the vegetation, notably on the strong leaves of the tupaki, growing abundantly on the sides of the road. At first the leaves were only bespattered with mud, further on they were perforated by the small stones, still further on the fleshy portion had been beaten out, leaving only the midrib, while beyond this not a vestige of a leaf had been left on any of the bushes.) The bed of the Wairoa Stream was filled with mud,

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and its exit from Rotokakahi so raised as to prevent the outflow of water. The water of all the lakes was grey and turbid, from the semi-liquid mud which had been precipitated into them. On the shore of the Tikitapu Lake was a thin liquid rim of what appeared to be gravel, but which on closer inspection proved to be small fragments of scoria and a few quartz crystals, washed from the mud deposit by the waves caused by the storm. Already the mud had begun to descend the steeper mountain sides in avalanches, with loud rattling noises.

The Material composing the Ejected Matter.

Having viewed the deposition of the material, we will now consider its structure and composition.

We have, first, the dry ash laid in the vicinity of Rotomahana (south side), and extending in a gradually reducing thickness to Galatea. Then the mud precipitated over the Wairoa, Rotoiti, Okareka, and Okataina. The dry ash carried in the shape of fine powder over Tauranga, and as coarse sand at Whakatane and Opotiki. Then we have a secondary coating of mud overlying the dry ash in the immediate vicinity of the geysers at Rotomahana, and the varying degrees of fineness of the ash deposited at long distances—notably at Whakatane, where a coarse sand fell for the first few hours, followed by a very fine dust for some hours afterwards. The same circumstance, but in a less conspicuous degree, was noted at Tauranga. In the order as arranged, we find the mud to be chiefly composed of quartz, in the form of fragmentary rock crystal; and as sinter, both white and coloured pink by peroxide of iron; together with a large amount of volcanic scoria in fine fragments, and exceedingly vesicular. This fragmentary scoria we shall find to be in very different proportion as we proceed, and the greatest interest will be felt in this fact, together with its bearing on the future fertility of the soil on which it has fallen, or will itself have replaced. We have not, however, found pumice to any large extent. In some of the older fragmentary rocks isolated patches were attached, but the fine deposits are singularly free from it.*

In addition to these varieties of ash, we have also the solid portions of stone which have fallen, not merely in the vicinity, but also at long distances from the scenes of eruption. The materials thrown out vary considerably. In the immediate neighbourhood of the craters are to be found stones from a few ounces to over a ton in weight. These vary considerably in

[Footnote] * Some few specimens of newly-formed pumice were afterwards found scattered over the ash-fields, but the quantity is so small as to escape any but the most careful search.

[Footnote] † Some have since been found which would weigh nearly 10 tons.

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formation, but are all portions of the rhyolitic rocks adjacent—a fine-grained tuff and coarse-grained brecciated trachytic rocks being plentiful. In the Wairoa, however, we find both scoria and the cross-grained trachyte just alluded to; while on the eastern end the principal solid material is composed of a basic scoria, in the form of lapilli. Returning now to the examination of the mud and ash, we find that the deposits at Okaro, Wairoa, Tikitapu, and Tauranga are very similar in appearance, being composed very largely of silica, both in the glassy solid crystalline form and as sinter; together with a small but varying proportion of scoria. Coming next to the deposit at Matata and Whakatane, we find the silica in the same forms, but the scoria has increased considerably in proportion. Advancing still further eastward to Opotiki, we find the same characteristics, but the scoria has still further increased in its proportion to the uncombined silica.* Now, if we turn to the analysis we have made of the materials obtained from the places mentioned, we find that they bear out the results of our optical examination. Clearly the ash from Okaro, Wairoa, and Tauranga are of the acidic group, while those from Whakatane and Opotiki are more nearly approaching the basic form. Again, the scoria obtained from Wairoa, and also from the southern end of the eruption, are undoubtedly basic, and have been thrown out in exceedingly large quantities, viewed from the amount and composition of the eastern deposits. Now, hitherto we have had the whole of the rocks of this region placed in the acidic group, and certainly no large mountain masses of a basaltic character could well escape the practised eyes of Von Hochstetter, or the members of the Geological Staff of our Colony. We are therefore forced to the conclusion that large quantities of basaltic scoria were ejected from the Tarawera volcano, or mountain, at the earlier stages of the eruption on the morning of the 10th of June. This is fully borne out by the numerous eye-witnesses, who unanimously speak of columns of fire rushing up from the newly-formed craters, and masses of fire bursting and falling back and around the sides of the mountain. That there was no outflow of molten lava actually discernible after the night in question is accountable by the enormous rush of high-pressure steam carrying off the molten mass in a fine state into the air, where it was carried away by the strong south-west wind which had now commenced to blow, or by being covered up by subsequent deposit of ashes.

We see from the foregoing that we have had two distinct eruptions, the one hydrothermal, the other volcanic, throwing

[Footnote] * The deposit found on the shores of Rotoiti contains large quantities of fine scoria, and as the mountains are approached this increases in quantity and the size of particles, until, on the top of Ruawahia, scarcely anything else is found.

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out differently rocks, acidic and basic, the physical characters of these rocks being as different as their chemical composition. Thrown to a great height, they were caught by the wind-storm and borne along by it in parallel lines from whence they emanated, the acidic to the westward and the basic to the eastward, more or less admixed in the centre, but slightly commingled on the extreme outer edge of the line. In this order they advanced, and in this order were precipitated on the lands over which they passed. Coarse sand, finer particles, dust: thus it was laid, in the order most to be desired by the agriculturist. So fine, indeed, is a large portion of the deposit, that the elements of nutrition in it are available for vegetation almost as soon as the first rains have carried it into the soil; while the particles not so exceedingly fine are already being attacked by that wonderful disintegrator, carbonic acid. For a moment let us glance at the basaltic lava cones in the vicinity of Auckland; and here we find the richest land, capable of growing extensive crops. The more decomposed, the finer the particles, the greater the amount of disintegration: the richer the ground, the greater the profusion of the elements of fertility. And this is the material which has been so lavishly spread over the land on the eastern portion of the district, and which is so largely intermixed with the acidic matter which has fallen over the western. That this rock in its unbroken, undecomposed form, is nearly valueless for plant life we can learn, by turning to the basaltic floes and cinder deposits of Rangitoto; but even there, in the few gullies where rain has washed the dust, and given depth of friable soil for plants to live in, where will we see a richer profusion of vegetation? The result of this downpour over so large an area need not dismay us, but rather give cause for rejoicing that, in the majority of instances, a richer soil has been added than formerly existed; and so lightly and finely has it fallen, that the winter rains will not have passed before it will have been washed into the soil to invigorate the new vegetation and improve the pastures, except in close proximity to the scene of the eruption. Even here we have shown that these deposits are capable of supporting vegetation.

Probable Cause of the Eruption.

To hazard a theory for so stupendous a cataclysm without first obtaining the most complete data on which to build, would appear reckless and unscientific; but the amount of data already accumulated, and the certainty that many months must elapse before a complete investigation of Tarawera and Rotomahana can be made, prompts us to advance a theory based on known laws, the working of which has been a source of wonder and attraction, and of world-wide interest, centring in Rotomahana. Here, as we are well aware, rose the beautiful terraces of Te

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Tarata and Otukapuarangi; here also were geysers, ngawhas, mud-springs, steam-holes, solfataras and fumaroles, each and all pouring out in larger or smaller quantities its volume of heated water until the lake itself was fully deserving of its name, “Rotomahana,” (warm lake), and its effluent Kaiwaka was worthy of a similar distinction. Now, the body of water debouching from this lake was large and continuous, and many millions of gallons were daily discharged into the Tarawera Lake. If now we turn to Rotomahana, and witness the effects of these hot springs and geysers, we find an amount of sinter deposited which is surprising, for though we have been used to speak of the two terraces, there were several others in a state of decadence or fragmentary condition, while lavishly around us were the evidences of sinter deposit. Year after year, probably for centuries, had this deposition gone on, though only a tithe of the silica which rose in solution had been arrested. Fortunately these waters have been analysed, the results of Mr. Skey's examination showing the water from the White Terrace to be charged with mineral matter to the extent of 144 grains to the gallon, and from the Pink Terrace 154 grains. Accepting this as equal for all the springs so constantly at work, we shall have in the course of years a very large amount of rock material withdrawn from the earth, most probably leaving cavernous spaces, and a weakening of the earth's crust locally. It required then only some local disturbance of the earth's crust to precipitate the falling-in of these spaces, which would have occurred sooner or later without such disturbance.

There can be no question that the first outbreak came from the Tarawera Mountain, caused probably by some slow-moving earth-wave, evidences of which we have already adduced. This in itself was sufficient to cause a precipitation of the weakened honeycombed rocks through which the waters of the Rotomakariri Lake would make their way into the chasm, and, coming into contact with a large surface of the molten rock, would be followed by a terrible convulsion, the escaping steam ripping up the side of the mountain in the manner already described. Water rushed down on the heated rocks only to be driven back and dissipated into the surrounding space, together with the fragmentary matter and dust resulting from the shock. The water from the Rotomahana Lake would then be driven up, together with the steam and debritic mass, to fall over long distances in the form of mud, as we now see it, until the water had been repelled from the lake, and with it the solid material of its bed. By this action the bed of the lake has been lowered, and its sides greatly extended, while there can be but little doubt that the whole of the terrace formation has been swept away.

That the long dormant mass of molten lava underlying it extended no further, is very questionable, and the evidences of

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the further extension in a S.W. direction are shown by the length of the rift extending to Rotomahana, thence by its entire length, and finally proceeding in the direction of Okaro Lake for a mile and a half. Here we find its effects very violent, the active craters already described not being built up, but blown directly out of the rhyolitic rock.

But all speculations of this kind are premature, in view of the paucity of information with regard to the present state of the interior of the lake crater. We merely bring them forward to incite inquiry, and thereby arrive at the whole truth of the questions involved.

We cannot close without a tribute to the memory of the dead. That this disaster should have had so fatal a result is a matter of great sorrow. Awoke by the roaring of subterranean thunder, by repeated shocks of the moving earth, awed by the fearful scenes of fire and lightning, apparently emitted by a mountain close in their vicinity, with hope of escape cut off, and the despair and uncertainty of unknown and unexperienced terrors, not less than 102 of the poor Natives must have gazed in fear; until with a terrible roar the lake beside them was belched out to cover and obliterate them, their villages and lands, and leave no trace of what had been their homes and cultivations for many years.

Nor can we think without deep regret that some of those Europeans at Wairoa who had viewed the grandeur of this wonderful outburst for hours, from apparently so safe a position, should have succumbed to the storm which raged so soon afterwards. Long, indeed, will it be before the name of Wairoa will be forgotten, or the memory of this beautiful valley, which was transformed into a mournful desert in a few hours.

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Analysis of Volcanic Ash and Lapilli from the Tarawera Eruption.
By J. A. Pond, Colonial Analyst, Auckland District.
Dust Ash or Mud Lapilli
1. 2. 3. 4. 5. 6. 7. 8.
Soluble on heating in hydrochloric acid and water, equal quantities— Okaro. Wairoa. Tauranga. Whakatane. Opotiki. Wairoa. Pareheru. Rotoehu.
Silica .35 .20 .35 .65 .60 .50 .70 .50
Iron Oxides 2.05 2.50 3.00 2.90 3.20 3.90 3.85 3.50
Alumina 3.45 2.80 5.01 4.45 3.90 3.70 4.95 6.60
Lime .95 .67 2.01 1.92 2.10 1.79 2.14 2.65
Magnesia .20 .30 .30 .47 .80 .67 .45 .70
Soda .33 .37 .58 .64 .59 .70 .84 .67
Potash .16 .19 .18 .17 .17 .14 .16 .09
Chlorine .05 .07 .03 .04 .06 .04 .05 -
Phosphoric Acid .09 .09 .14 .095 .125 .16 .125 .06
Sulphuric Acid .39 .32 .48 .35 .30 .22 .41 -
Carbonic Oxide Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr.
Organic Matter 1.30 1.30 .90 .20 .25 - - -
Water .85 .90 .75 .30 .15 - .25 -
Insoluble in acid—
Silica 66.50 69.90 63.65 56.50 55.70 50.4 50.65 52.10
Iron Oxides 4.00 2.65 4.20 8.65 8.30 10.20 10.65 9.20
Alumina 14.50 13.15 13.15 13.90 13.80 16.30 13.25 11.70
Lime 2.90 1.93 3.41 6.44 6.35 8.59 8.12 8.40
Magnesia Tr. Tr. 1.60 .90 1.40 2.10 2.65 3.95
97.07 97.34 99.74 98.57 97.795 99.415 99.245 100.12
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Analyses of Volcanic Ash and Lapilli from the Tarawera Eruption.
Analysis made by J. A. Pond, Colonial Analyst, Auckland District.
Pond and Smith.—On the Eruption of Mt. Tarawera.
Form. Locality. Silica. Iron Oxide. Alumina. Lime. Magnesia. Soda. Potash. Chlorine. Phosphoric Acid. Sulphuric Acid. Organic Matter. Water. Total.
Ash 1. Okaro 66.85 6.05 17.95 3.85 .20 .33 .16 .05 .09 .39 1.30 .85 97.07
Mud 2. Wairoa 70.10 5.15 15.95 2.60 .30 .37 .19 .07 .09 .32 1.30 .90 97.34
Dust 3. Tauranga 64.00 7.20 18.16 5.42 1.90 .58 .18 .03 .14 .48 .90 .75 99.74
Ash 4. Whakatane 57.15 11.55 18.35 8.36 1.37 .64 .17 .04 .095 .35 .20 .30 98.57
" 5. Opotiki 56.30 11.50 17.70 8.45 2.20 .59 .17 .06 .125 .30 .25 .15 97.795
Lapilli 6. Wairoa 50.90 14.10 20.00 10.38 2.77 .70 .14 .04 .16 .22 - - 99.415
" 7. Pareheru 51.35 14.50 18.20 10.26 3.10 .84 .16 .05 .125 .41 - .25 99.245
" 8. Rotoehu 52.60 12.70 18.30 11.05 4.65 .67 .09 - .06 - - - 100.12
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Art. XLV.Notes on the Eruption of Tarawera Mountain and
Rotomahana
, 10th June, 1886, as seen from Taheke, Lake
Rotoiti.

[Read before the Auckland Institute, 26th July, 1886.]

During the first week in June the weather was stormy, the wind being N.E. to N.W. and W., with a moderate rainfall. On the 6th of the month the wind changed to South, and clear cold weather set in. This continued to the morning of the 9th, when the wind hauled back to West, blowing a stiff breeze, with a cloudy sky. In the afternoon there were several sharp rain-squalls, but the night set in fine, the moon being just in her first quarter; and an occultation of Mars, which occurred about 9 o'clock, was clearly seen. The wind at this time was light. At about a quarter past 1 o'clock on the morning of the 10th I was awakened by an earthquake. This was followed in a minute or so by a much heavier shock, which aroused everyone in the place; and then there succeeded, at intervals of about 50 secs., a succession of vibrations, varying in character, some being uniform undulatory movements, others sharp and irregular; while some resembled the striking of heavy blows upwards. This state of things continued for half-an-hour. About 1.45 I was startled by a steady roar, like that produced by a blastfurnace, or a great waterfall. A friend in an adjoining room called to me to look out of my window. My room was on the east side of the house; and upon looking out I saw that all that side of the heavens was aglow, and there seemed to be a great column of fire rising to a height of about 15 to 20 degrees, while above it was a dense column of black smoke. Masses of solid matter appeared to be hurled up, amid showers of both ascending and descending sparks. At the same time there was a marvellous electrical display, all the ordinary forms of lightning were there playing, as it were, through the flame, the white light showing conspicuously against the red. Over and on either side of this there constantly flashed rounded masses of dazzling white light, as if caused by the explosion of bombs, and bayonets of sparks, which crackled like fireworks. My first impression was that there was an eruption of the Tikitiri Springs, 2½ miles distant; but upon ascending a hill I made out the Whakapoungakau Range in the foreground, the trees on its summit being distinctly visible; and then I made out that the seat of action was Wahanga, the northernmost peak of Tarawera Mountain, some 13 or 14 miles distant. There was very little tremor of the earth at this stage. I went down to the lake shore, but could not detect any disturbance there. A

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gentle breeze was blowing from S.W., and in that direction the sky was perfectly clear. Later on the roar became louder, with crashing reports, as of heavy bodies falling; the thunder, too, increased, and the lightning was, if possible, more active. The shocks, too, were renewed with great vigour. At this time a dense black column rose on the right of the blaze—that is, more to the South, and in the direction of Rotomahana, and spread out in the sky. Soon after 3 o'clock the wind shifted to the South-east, and the black cloud was driven slowly in on the light, dropping over it like a veil, and by degrees blotting it out. For a time the lightning flashed through the murky mass, and then there came on the most utter and appalling darkness. The roar of the volcano could still be heard, and occasional tremendous peals of thunder; but these gradually died away. About 4 o'clock there was a pattering of light cinders on the roof, and a sulphurous smell was apparent. Upon going outside I found the air charged with fine dust, which was painful to the eyes. The night was intensely cold, and I went back to my room and slept for some time. On awaking I opened my window, and found the sill covered with a fine sandy mud. Some Maoris then, by the aid of lanterns, found their way to the house, and reported that their huts were being buried, and they feared that the roofs would fall in. At 8 o'clock there was still the most intense darkness, and no sound could be heard except an occasional rumble like thunder. The soft ooze was falling silently as snow, and covering everything up. At 9.30 there appeared a faint gleam of greenish light, low down in the South, and the wind having veered again to that quarter, the fall of sand gradually became less, and ceased altogether at 11 o'clock. By noon one could read a newspaper in the open air, but the position of the sun could not be made out until 2 o'clock. Throughout the day there were occasional tremors of the earth, and thunder and lightning in the East. All along the ridge of Tarawera immense masses of dark smoke were being belched forth, while to the right a great column of steam arose, and further south a smaller one. All round Rotoiti everything was covered with the grey volcanic deposit. In some places it was in drifts of 18 inches deep, and nowhere was it less than 3 inches. The fern and light shrubs in the open country were levelled with the ground, and in the woods every leaf and spray was covered. The telegraph wires were coated, and looked like ropes an inch thick. Numbers of straight dead tree-trunks were burning like great torches. The lake had become a soapy-white colour, and had risen 3 or 4 inches, the water being unfit for domestic use.

On the 11th and 12th of June there was a hard cutting south wind, bitterly cold. Light shocks were felt. Great

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numbers of koura, and myriads of the small fish found in these lakes, were washed on shore dead or dying; many of the fish, though not dead, presented a bruised and discoloured appearance. All the small birds had disappeared; pheasants and Australian quail came almost to the doors of the houses seeking food, and numbers of rats were wandering about the hills and valleys.

There is no tradition of any activity in Tarawera Mountain, nor of any alteration in Rotomahana. The mountain was in past ages the chief burial place of the Ngatirangitihi tribe, the section of the Arawa to whom the country about the east end of Tarawera Lake belongs. Apumoana, the eldest son of Rangitihi, the great ancestor of all the Arawa tribes, who lived about fifteen generations ago, was buried in a cave on the rim of a crater there. It has been said, I believe, that the names of the different peaks of the mountain suggested some volcanic activity during the period of Maori history. I cannot see the connection myself; but, in any case, Maori names of places do not necessarily point to the literal meaning of the name. For instance, the name Rangitoto—literally, sky of blood—is thought by some people to denote that the Island of that name near Auckland was in a state of volcanic activity when the ancestors of the Maori came from Hawaiiki. But the word “rangitoto” also means “scoria” or “cinder,” and there are several places in the North Island so called where there is no scoria or cinders. Where the meaning is not palpable, great caution and research should be exercised in tracing the reasons for the names of places and things, or one may commit a great blunder. For instance, the author of the “Aryan Maori” considers that the moa (Dinornis) was so named from moana (the ocean), on account of its vast size; but he would hardly have ventured that opinion if he had known that in the Samoan Group “moa” is the name of the domestic hen.

Art. XLVI.Thermal Activity in the Ruapehu Crater.

[Read before the Auckland Institute, 26th July, 1886.]

During my last season's work in the triangulation of the King Country I had occasion to ascend Ruapehu, to include a trig. station on Paretetaitonga, one of its southern peaks, with our system of triangles. It was not my intention to attempt a geological examination of the mountain; but the few notes which I was able to make in the short time I could devote to the

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subject will be of interest, chiefly as disclosing the fact that the volcanic forces considered to be long since spent on Ruapehu are still active, in at least so far as the solfatara stage is concerned.

It was not until the 9th April that the snow on the lower slopes of the mountain, where it is usually too soft to walk over, had sufficiently melted off to allow of an ascent. We made a start on the 9th, following up the valley of the Whakapapa River for some three miles to an open plain at the foot of the mountain, covered with native blue-grass (Patiti) and tussock; here we left our horses, and travelled on on foot for about four and a-half hours, crossing over lava ridges and deep ravines in a southerly direction, to reach a long prominent ridge which ran down in a tolerably regular line from the top of the cone to its base. Finding a convenient camping-ground in a deep ravine, where a small tongue of the stunted bush which covers the lower western slopes of the mountain runs up into the gorge, we camped for the night to await the first opportunity of clear weather for our ascent. The next morning a thick heavy fog hung over the mountain, and came down throughout the day in a drizzling rain, which, however, cleared up towards evening, and there was a hard frost during the night. The morning was beautifully clear, with a cloudless sky. We left our camp while the stars were yet bright, as we had 4,000 feet to ascend, our camp being about 5,000 feet above the level of the sea, and very nearly at the limits of vegetation. For about an hour and a half we followed up the gorge, shut in on both sides by high precipitous rocks and ridges of lava, over which it was difficult to get a passage. At the head of the gorge, however, we found a practicable passage, and reached the back of the spur we had selected for our ascent just as day was dawning.

The scene was indeed a magnificent one, as the first rays of the sun lit up the snowy peaks towering high above us, and gradually shone over the snow-fields and great dark ridges and gorges of the mountain. All around us were examples, most varied and instructive, of volcanic phenomena, and the forms and shapes assumed by the cooling lava. The ridge on which we stood was probably built up by the most recent eruptions from the mountain, formed of alternate sheets of lava and layers of ashes; at its base were immense masses of jagged scoria rocks, piled up in irregular heaps and presenting most grotesque shapes and forms. To the south of the ridge, and running down from under the snow, was a well-defined stream of lava, embracing in its course large blocks of half-molten rocks, around which the lava stream had cooled, giving them the appearance of stones standing in a river current. At the base of this flow was a most beautiful example of the columnar form assumed by cooling lava. A large mass of the cooling metal would seem to have become detached, and rolled

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down the mountain side in a separate mass, or boulder, from 70 to 100 feet in height; the outside of it presents a slaggy scoria-like appearance, becoming gradually closer and more compressed towards the centre. One side of this boulder has been broken away, probably from the masses of rock moving down the mountain side coming in contact with it, and thus the construction of the interior is exposed. It presents a most remarkable appearance, a number of long prismatic columns, about 9 inches in diameter, extend outward, radiating from a central point at the bottom to the top and sides in a fan-like fashion, somewhat in the form of a peacock's tail, fitting closely together at the centre, the space between them widening towards the outside; they are intersected by transverse cracks, which divide them into various lengths; some of them can be moved and replaced; though being of various lengths the regularity and symmetry of the portion exposed is very striking and wonderful. About half a mile to the northward of the ridge we were ascending, another lava stream appeared to have cooled running down over the ridge, and to dip down on the lower side of it in the same direction as the slope of the underlying rock, giving to the lava-flow the appearance of a waterfall in the distance, at the foot of which great masses of scoria were piled on top of one another in a confused irregular fashion. The effect of frost upon the rocks became more apparent as we went higher up the mountain; masses of trachytic lava lay in heaps and ridges, broken up into fragments as if struck by sledge-hammers; the travelling was difficult, and sometimes accompanied by danger, over these masses, which would give way beneath the hands and feet, and roll down in large quantities.

We reached the perpetual snow-line in about three hours from our camping ground. There was yet about 2,500 feet to ascend, but the remainder of the ascent was all over the frozen snow, and not very difficult. The ridge was rather narrow in places, whilst on both sides of it steep snow-fields sloped away many hundreds of feet, terminating over the rocky precipices which girt the base of the mountain. Our party were five in number, and we travelled over the snow in “single file,” a long rope fast from one to the other to guard against accident, lest either through a caving-in of the snow or by a false step any of us should slide down over the steep snow-fields. It took five hours from our camping-ground to reach the summit.

The weather was still beautifully clear when we got on top, and the view in all directions around us was truly magnificent. To the westward, the snowy cone of Mount Egmont was very conspicuously prominent, its distance from us being 73 miles. We thought we could distinguish the houses at Waitara with our telescopes; and some of our party suggested that a column of smoke which we saw rising up there came from the

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chimney of the Auckland Freezing Company's establishment. The sea was visible beyond the east and west coasts, and all the successive mountain ranges and river valleys in both directions could be traced out with our telescopes. The rugged peaks of the Kaimanawa Mountains, extending for many miles away to the eastward, looked rather insignificant beneath us, although their height varies from 4,000 to 6,000 feet above the sea. The crater of Ngauruhoe, nine miles to the north of us, looked like the dilapidated chimney of some vast furnace down into which we were looking. Taupo Lake, which I have seen described as “a vast inland sea,” as seen from some of these mountains, looked quite small from our great height. The distant peaks of Pirongia, Te Aroha, and other prominent features of the Lower Waikato District looked but a short distance away from us, considering they were over 120 miles off; and as all our party hailed from that direction, each took pleasure in recognizing the familiar landmarks which surrounded his own home, and which he had not seen for many months past. The comparatively low country lying between us and the west coast, though intersected by deep valleys and mountain ridges, seemed rather like a level plain, and, as one of our party remarked, “the mountains only looked like potato ridges.”

The exact form and construction of the top of Ruapehu it would be impossible to describe, the whole mountain-top being covered in a deep mantle of snow. The view presented to the eye is as follows: three prominent peaks, one to the extreme north being exactly a mile distant from where we stood, and not quite so high as the peak we were on; another half a mile to the eastward of us, somewhat higher than ours. Paretetaitonga itself, on which our station is, is a very sharp pointed peak, formed of loose masses of probably trachytic lava, broken into all shapes and sizes by the action of the frost. It has an almost perpendicular inner face, so much so that the snow seldom rests against it, and is soon thawed by the heat of the sun on the rocks during the daytime. Between these three principal peaks lies a snow-field of unknown depth. This snow field is intersected by long crevasses running in all directions through it; they are from 10 to 30 feet in width, and run to great depths; some that we saw, I should think, were several hundred feet deep.

Deep down in a crateral hollow of basin-like shape, its steep sides covered with perpetual snow and ice, is a pool of water of a greyish-cream or drab colour. From the trig-station we overlooked this lake, the peak on which we stood being the south-west portion of the old crater-lips which surround the lake. From its peculiar surroundings of snow and ice, it was difficult to estimate with any degree of accuracy the diameter of the lake, and time would not allow of a proper measurement. It appeared

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to me to be nearly of a circular form, and 500 feet or more in diameter. It was quite impossible to descend to the lake, except by the aid of a long rope, and even then the descent would be attended with danger and difficulty. When I got on the top of the peak I noticed little clouds of steam rising from the surface of the water. On watching more closely, the water appeared now and again to assume a rotatory movement, eddies and whirlpools passing through it from the centre to the sides, and steam flashing up from those eddies, leaving little doubt in my mind that the water was in a boiling state. Close to the water the sides of the crater are bare of snow, and appear to be formed of loose particles of rock and volcanic ash; above are steep inclines of snow, sloping in all directions towards the water and terminating in icy masses overhanging the lake. The masses of ice show, in the cracks and crevasses which intersect them, and in their fringes of icicles, the effect which the heat from the lake has on them.

We had not very long been engaged in trigonometrical observations at the trig-station before a heavy cloud rolling up the mountain side enveloped the peak and covered us almost in darkness, so that we could not see one another ten yards distant. Whilst we sat on the mountain top waiting for this to clear away and allow us to complete our observations, a portion of the icy mass surrounding the lake, breaking away from its position, crashed down over the precipice into the lake below, sounding with an awful and solemn effect amongst the stillness of all around. As the dense cloud continued to hang on the peak, and the time had arrived for us to start back for camp, we were obliged to leave our work for another day and commence our descent. I may mention as a curious fact that on top of one of the highest peaks of Rua [ unclear: ] ehu we found, on a ledge of ice, the remains of a rat in a good state of preservation, the skin only being devoid of the fur, and a portion of it still remaining on the chest, across which the fore-legs were folded.

As I mentioned before, the snow-fields which fill up the crateral hollows of the mountain prevent the possibility of judging what the shape of the top is; but from the vertical inward faces of the peaks which can be seen, and the outward appearances lower down the mountain on the western side, it would seem rea [ unclear: ] onable to infer that they surrounded a great central hollow, and that the mountain had been a truncated cone, large portions of the sides of which were blown away by eruptions; and that subsequently, inside the remains of the old cone, two or more craters had broken out and built up new cones. The vent in which the thermal action still continues seems to be the last crater which was active, judging from the appearance of the lava streams down the mountain side. Around the lower slopes of the mountain, and underneath some

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of the lava flows, are immense beds of consolidated tuff; on the lower slopes the soil of volcanic loam is forming.

The waters of Wangaehu have a sulphurous taste and smell. Its course can be traced down the eastern side of the mountain from nearly the top of the cone in which is the hot lake; it may therefore be inferred that the water receives its character from this lake, through a subterranean passage in the mountain. Since discovering that the crater contained hot water, I have mentioned the fact to the oldest Natives in the district, and they all concur in the belief that it is something new. I am, however, inclined to doubt this, and to believe that a low volcanic heat must have prevailed there throughout. Five years ago, when engaged in triangulation on the Kaimanawa Ranges, I noticed hanging over Ruapehu, in the position of the crater, what seemed to be a cloud mass. This I remarked more than once, but I did not know of the existence of the lake at that time, and I considered that it must be a cloud or fog rising through some of the gorges of the mountain, although it closely resembled a column of steam. I may also mention that some eighteen years ago, (I am informed), an abnormal flood occurred in the Wangaehu River, carrying down with it large blocks of snow and ice. There had been no heavy rains at the time to account for this flood: it is therefore reasonable to infer that it was caused by an escape of the warm water from the lake, passing down through some underground passage below the edge of the water, and thawing the snow and ice on the mountain side. This, however, appears certain, that before or about the beginning of April, a considerable increase of volcanic heat in the Ruapehu crater took place, which continued to increase until towards the end of May, after which time I had no opportunity to observe it.

On the 16th of April I noticed a well-defined column of steam rising from the crater, several hundred feet above the mountain top; it was also visible several days subsequently. I showed it to several of the Natives, who said they never had known of such a thing before. If it were of common recurrence, and in such volume, I think it impossible that it could have escaped the notice of the Natives.

On the 23rd May, the weather being very clear and bright, a larger column than usual ascended from the crater, about 300 feet above the mountain, spreading out horizontally into a cloud-like mass, the outside portions of which descended again and rolled down the mountain side. Towards noon this column began gradually to decrease, until it disappeared altogether by sunset. Since the end of May the dull weather prevented any further observations of the mountain. Should the volcanic heat so increase as to cause a sudden thaw of the ice and snow which fill up the crateral hollows of the mountain and mantle its sides for several thousand feet, the result must be heavy

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floods in the Wangaehu, Waikato, and Wanganui Rivers, probably attended with serious consequences to the town of Wanganui. The great boulders in the Whakapa and Wanganui Rivers, some of them weighing over 50 tons, would seem to have been carried down by such floods in the past. That the atmospheric conditions affect the state of the thermal springs and fumaroles in the Tongariro group appears very evident. I had not sufficient opportunity of noting the state and conditions of the steam-vents, under various atmospheric conditions, to make any definite statement on the subject, but I noticed that the discharge of steam was greater in the early morning with southerly winds and frosts; and the Natives always look for bad weather when the steam hangs low on Ngauruhoe in the morning.

Art. XLVII.Phenomena connected with the Tarawera Eruption of
10th June, 1886, as observed at Gisborne.

[Read before the Auckland Institute, 26th July, 1886.]

About 2h. 30m. a.m. on the morning of the 10th June, 1886, most of the inhabitants of Gisborne were roused from their slumbers by the rumble of distant explosions, following one another in quick succession, accompanied by an extraordinary agitation in the atmosphere, (there being no wind to speak of), which kept the doors and windows rattling in their frames, as though from the effect of a discharge of heavy artillery in the neighbourhood. The first probable cause that suggested itself was thunder; but, on looking out, it was seen that the sky was perfectly clear and the stars shining most brilliantly. Then, if it was not thunder, might it be the forewarning of a violent earthquake? But the atmospheric disturbance showed that it could not be a mere earth-rumble; and so the conclusion was forced upon one that it must be a distant volcanic eruption, probably from Tongariro.

A further survey of the horizon, however, showed a cloud low down in a W.N.W. direction, in or near which there was something unusual going on; flashes of light illuminating the whole cloud; then linear flashes darting in various directions, or round balls of light. As the view of the cloud was somewhat obstructed by trees, we could only see the upper part; and concluded that, wherever the eruption might be, there was a thunderstorm of an unusual character raging in that direction in the far distance. Other people, who had an unobstructed

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view of the W.N.W. horizon, saw much more of the fiery display than I did. Accounts given by different people vary somewhat; but this is probably owing to the difference of time at which the observations were made. Those who had an early view, about 2h. 30m. a.m., describe the cloud as shaped somewhat like a mushroom, the lower portion forming a distinct column, while the upper part spread itself out on all sides. The flashes, or incandescent objects, also were seen to be projected from below into the upper part of the cloud, and some of them to fall again, and others apparently to explode, many of them presenting decidedly the appearance of balls. After a time the cloud became more diffused, and no longer maintained the mushroom shape. Between 3 and 4 a.m., a south-west squall came up, with heavy rain, which effectually put a stop for some time to further observations. A number of slight shocks of earthquake were experienced at intervals, some persons having counted as many as twelve between 3 o'clock and noon.

Towards morning it was observed that there was an unusual darkness, though there was a low comparatively bright arch in the south-west horizon. At 7 a.m., when it should have been broad daylight, it was still exceedingly dark, but near objects on the north-east side were dimly lighted up by a weird reflection from the south-west horizon, the light taking a very peculiar colour from the cloud overhead. It was evident now that we were under the edge of a dense cloud of volcanic dust, which shut off the sunlight very effectually, with the exception of what came to us in a roundabout way by the south-west. Under the influence of the south-west gale, which had now set in decidedly, the dense dust-cloud gradually moved off to the north-east, and by 10 a.m. we were able to dispense with artificial light.

There were frequent squalls and showers from the south-west during the day; but nothing further was seen of the eruption, though the rumble of the explosions continued to be heard from time to time during the day, and for several days afterwards.

On the evening of Sunday, 13th June, the horizon being clear, there was visible a distinct column of vapour or smoke in the W.N.W., which formed a diffused cloud above.

There has been no fall of dust or ashes in Gisborne, though there was a sprinkling at places about fifteen miles off in a north-westerly direction, and, of course, more further on. The southern limit of the deposit on the coast is Anaura. At Waipiro, in Open Bay, dust came down from about 4 a.m. to about 10h. 30m., causing the most intense darkness, until it was gradually driven off by the south-west wind about 11 o'clock. The deposit there is about 1 inch thick on an average.

According to the best available maps, the distance in a direct

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line from Gisborne to Tarawera is just 90 miles; the height, therefore, of the cloud of vapour and dust which was visible here at the time of the eruption must have been very great. An object at that distance, to be visible at all on the horizon, must be at least one mile in height above the level of the sea. It is not possible to obtain an absolutely correct measurement of the height of the cloud above the horizon, but a close approximation can be arrived at by the aid of other objects with which it could be compared. In this way it appears that the angular measurement of the height of the cloud, as seen from Gisborne, was from 3 ½ to 4 degrees, corresponding to a height above the plane of the horizon of from 5.5 to 6.3 miles. For the full height, we must add to this the distance between the plane of the horizon and the top of the mountain, which will bring the whole height, at the lowest computation, to a little over 6 miles from the top of the mountain.

Art. XLVIII.Notes on the Eruption of Tarawera, as observed at
Opotiki.

[Read before the Auckland Institute, 21st July, 1886.]

On 10th June, 1886, at about 2 a.m., people were aroused by violent noises as of peals of thunder, and volcanic rumblings, and towards the south-west the sky was illumined with strong light, from the midst of which at intervals shot forth balls and forks of fire.

From about 2 till 9 a.m. there was a succession of shocks of earthquake of moderate force, accompanied by a peculiar floating or rolling, as it were, of the earth.

At about 3 a.m., the sky at the time being perfectly clear and starlight, an inky-black cloud rose in the south-west and drifted towards the north-east, and gradually quite overspread the heavens; and a rain of fine ash, and subsequently dust, commenced, which lasted till noon, and covered the Opotiki district to a depth of about 1 ½ inches. The air was unusually cold. It was pitch dark till 10.20 a.m., at which hour the fall became slighter and daylight gradually appeared, and the rest of the day was twilight.

Animals were greatly distressed, and cattle gave vent to constant bellowings. Many small birds died, and insect life suffered severely.

No tidal disturbance was noted.

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At Orete Point, 45 miles north-east as the crow flies from Opotiki, Mr. Seccombe describes the morning of the 10th June to have been clear, and at about 8 a.m. the cloud of dust caused darkness, and a layer of ashes and dust was deposited of about the same depth as at Opotiki.

“Opotiki, 22nd June, 1886.

My Dear Mr. Dumerque,—

“I kept rough notes of what I experienced on the morning of the 10th instant, and give you them with pleasure.

“It was fine bright moonlight up to 10.30 p.m. of the 9th, when I ‘turned in.’ Between 3 and 4 a.m. of the 10th I was aroused by a noise like distant thunder. I took little notice of it for a time; but as it developed it became occasionally a continuous roll, broken at intervals by explosions resembling heavy artillery fire. Cattle were bellowing and horses neighing, and it became quite evident that a storm of unusual character was brewing. This much could be surmised while lying in bed. What appeared to be gentle rain was heard falling on the trees near the window, but it was never heavy; and the thunder seemed to remain in the same spot. The usual sound of the rain running off through the spouting was conspicuous by its absence, and created surprise in my mind. The lightning was bright and the thunder loud, but between the peals at times the noise as of distant artillery-fire was audible. Mild shocks of earthquake were also noticeable about every half-hour. I rose at 4.30 a.m., and went into a room with windows facing South and West, and a cold, damp, sulphurous smell led me instinctively to open the window facing South an inch or two and feel the sill. There could then be no longer any doubt as to what had occurred, as a thin sprinkling of sand could be felt outside. It was intensely dark. I then procured a lantern and made my way into the street, which I found evenly covered with a thin coating of dark and fine sand, which was falling gently; and, while it thundered, the sand seemed to fall faster or thicker.

“There was a strong sulphurous smell outside, and the wind blew cold and in gusts.

“About due South a dull flare-up could be noticed occasionally through the falling sand and dust. This led me to think I was at the wrong side of the house, and that it was the glare from an eruption on White Island; but I soon discovered that nothing was to be seen towards the North.

“At 6 a.m. my aneroid barometer stood at 30.05°, and the thermometer at 50° in the office.

“Roosters all round were crowing vigorously from 6 a.m. till daylight came.

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“Having read in a late paper that Ruapehu had been seen smoking, I concluded that either that mountain or Tongariro was in violent eruption. Moreover, the mild earthquake shakes, and the fineness of the sand and dust, showed that the disturbance must be a long way off. These reflections were sufficient to prevent alarm. A peculiarity about some of the earthquakes was that the house seemed to be afloat. I found that a scissors suspended by a nail in the wall gave frequent notice of shakes that would not otherwise have been apparent.

“Up to 9.30 a.m. it was dark as pitch, but shortly after-wards showed signs of clearing, and by 10.30 a.m. there was twilight, which gradually brightened until the place where the sun was could be distinguished. The sand and dust penetrated the house, and covered everything.

“From 10 a.m. there was a calm until 2 p.m., when the wind blew lightly from the south; and there was not much more than twilight all day.

“At 5 p.m. it cleared to the eastward, but a thick bank of fog was visible in the west. The night was calm, and cool, and fine, and slight earthquakes were felt occasionally.

“The storm had rendered the telegraph wires useless, and we had no communication with the outer world for about 24 hours. Very little alarm was felt generally, and there was no panic.

“Careful measurements of the depth of sand and dust show that about 1 ½ inches had fallen in town; but it is reported to be deeper on the table land.

“On the morning of the 11th, which was bright and clear, an immense cloud of steam was seen in the west, and it was rightly guessed that Rotomahana was the seat of the volcanic disturbance.

“The sand is nearly black, and lies under the dust, which is of a light mouse colour, and the layer of the former is twice as thick as that of the latter. This sand is precisely the same article that our forefathers, not so many generations back, used for the purpose of drying letters, when blotting paper was not so good or so common as it is now. And some years ago, when I was an office boy in a mercantile house in Old Broad Street, London, engaged in the Russian trade, several of our correspondents in the interior of Russia dried their letters with the same sort of sand.

“Yours faithfully,

“F. W.Henderson.

“E. P. Dumerque, Opotiki.”

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Art. XLIX.Traces of Volcanic Dust-showers at Napier, Petane, and generally throughout the East Coast Districts, North of Cape Kidnappers.

[Read before the Hawke's Bay Philosophical Institute, 12th July, 1886.]

The results of some recent experiments made by me upon the dark soils covering the Napier and Petane Hills, as also upon a dark sand deposit near Mr. Villers' hotel at Petane, may not prove uninteresting to members of this Society. For some time past I have been collecting data as to the extent and character of the pumice deposits of the East Coast District between Poverty Bay and the Manawatu Gorge, in the Seventymile Bush. Within this wide area there is ample evidence of comparatively recent volcanic products; but until examining specimens of the ejectamenta of the recent eruptions at Tarawera, in the Lake District, the thought had not occurred to me that possibly there might be evidence in our Napier hills of dust showers similar to those which have been experienced in the district extending from Tologa Bay to Tauranga, including the whole of the Bay of Plenty.

The Napier hills, or, at least, those portions of them that have not suffered from extreme denudation, are covered with a remarkable cap of what at first inspection seems to be a dark vegetable soil. When first broken up this soil is very productive; but this quality quickly disappears unless manures are plentifully used, there being little or no “body” in the soil. I had often wondered how such a cap of black soil came to be formed upon the hills, for only a small percentage is of vegetable origin; but on seeing several specimens of the volcanic dust and sands which fell upon the deck of the “Southern Cross,” on her way down from Auckland at the time of the Tarawera eruption, the thought at once occurred to me that possibly the black soil of Napier and surrounding district might be the result of similar showers of volcanic dust, at a time when the volcanic cones of Ruapehu, Ngauruhoe, Tongariro, Tauhara, and others were in a condition of activity. The results of my tests confirm this opinion; for I find that among the many tests I have made of the soils in and around Napier, a very large percentage, in fact the greater portion, are of volcanic origin.

My experiments were carried out in the following manner: I obtained from the edge of the Napier Bluff, and immediately underlying the turf, a small parcel of black soil, containing altogether about 20 ounces. This I moistened with water, and made up into a kind of paste. I then arranged five different receivers, one inside the other, so that the overflow of water

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from the smallest vessel might pass into the one next in size, and so on. Water was then allowed to run slowly upon the pasty mixture, which was stirred continuously, so as to drive off the vegetable matter and lighter products. The process was continued until nothing remained of the original soil except the heavier and insoluble sands and grits. After allowing the mud and lighter sands which had overflowed into the different vessels to settle, the water was drawn off, and the sediment or deposit contained in each was carefully collected and placed in an oven to dry. The same plan was followed with a number of other specimens from the hills where the lands had not been broken up, as also from other places outside Napier, and in each instance the results were very similar. The products, as far as I have been able to make out with any degree of certainty, are: pumice sands, magnetic iron sands (magnetite), lava, ashes, felspar, nepheline, leucite, and olivine. Under the microscope beautiful specimens of minute glass-like rod crystals of leucite were common, having a faint black or dotted line running through them similar to those described by Rutley.

It is a curious fact that the whole of the East Coast between Poverty Bay and Cape Kidnappers has a black soil similar to that covering the Napier hills, the only difference being in the thickness of the deposit, which varies from 4 inches to about 16 inches.

Since writing the foregoing, I have found at Petane a peculiar black sand or soil deposit, about 8 inches in thickness, interbedded with fine sands like those which form the highest beds at Battery Point, Napier. This black sand has a close resemblance to the black soil covering the surrounding hills, and but for the somewhat greater compactness of the former, due, no doubt, to pressure, it would be difficult to distinguish it from the present surface soils. I have washed specimens of this black sand, and I find that it also is of volcanic origin. Scoria, lava, obsidian, olivine, perlite, felspar, mica, and a trace of magnetite are distinguishable; but some of the sands I am still unable to identify. After washing, the sand is not unlike emery powder in appearance.

From the results of my experiments I feel convinced that the East Coast District of this island has been subject, at a not very remote date, to dust showers of volcanic ejectamenta. Had the wind been blowing from the north-west at the time of the recent eruptions, it is a matter of certainty that the dust showers which fell in the district extending in a north-easterly direction for about 120 miles from the seat of the volcanic outburst, would have fallen throughout the East Coast District as far as Napier and the Hawke's Bay river system. Within 75 miles of Napier there are many volcanic cones, including the semi-dormant Tongariro and the not– altogether–extinct cone of

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Ruapehu—the highest point of elevation in the North Island; and although this district is separated by the Ruahine chain of mountains, and other minor ranges, from what may be termed the zone of active volcanic phenomena, as represented by hot springs, solfataras, geysers, and burning mountains, it is certainly not outside the zone of volcanic influences, the effects of which may be seen at any time along the East Coast. A recurrence of activity in and about the district of which Lake Taupo is the natural centre, would undoubtedly bring showers of volcanic dust and débris as far as Napier, should the wind be blowing in this direction at the time; but I cannot agree with those who say that such showers would be detrimental to vegetation. They may cause temporary inconvenience, but of their beneficial effects in the production and formation of soils I think there can be no question for a doubt. To me, volcanic dust showers are blessings in disguise. They may cause loss and inconvenience at the time of their deposition; but they contain within their particles the elements of fertility, and only need, like wine, age to make them valuable adjuncts in the formation of rich soils.

Art. L.A Description of a Scaphites, found near Cape
Turnagain.

[Read before the Hawke's Bay Philosophical Institute, 11th October, 1886.]

On paying a visit to Wainui, a small township near Cape Turnagain, a short time ago, I found awaiting me at the schoolhouse a fossil, which had been sent there by Mr. John Fallahe, a settler residing in that district. He stated that the fossil had been found by a person named James Busby, in the bed of the Wainui Stream, about 10 or 11 miles from its mouth, and that it was thought to be, by those who had seen it, a fossil lizard. Indeed, it was so described to me by a gentleman in Porongahau several days before I had the opportunity of seeing the specimen. The end of the outer whorl of the fossil has the appearance of a lizard's head, and the inner whorls resemble somewhat the body and tail of the Hippocampus brevirostris, or Sea-horse, which is to be found in most places along the New Zealand coasts after heavy storms. The specimen, however, though having a great likeness to a vertebrated animal, is merely the cast of a shell belonging to the genus Scaphites, a genus closely allied to the fossil Ammonites, which had their chief development towards the close of the mesozoic period.

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The fossil is interesting, as being the first of the genus Scaphites found in New Zealand, and Professor Hutton thinks it is the first that has been found in the Southern Hemisphere. Further, it is interesting as settling the question of the identity of the rocks about Cape Turnagain and the valley of the Wainui Stream.

From a recent inspection of the rocks in the district between Kaikora, near Waipawa, and Pourere on the north, and the Wainui Stream on the south, I conclude that the rocks through which the latter stream flows mostly belong to the middle and lower cretaceous, and that the fossil Scaphites comes from the pale-blue and grey chalk which underlies the greensand.

I propose naming the fossil Scaphites hectori, in honour of Dr. Hector, the head of tke Geological Survey of New Zealand.

Key to the description of the fossil after Nicholson:—

1.

Class—Cephalopoda.

2.

Order—Tetrabranchiata.

3.

Family—Ammonitidœ.

4.

Genus—Scaphites.

5.

Species—Scaphites hectori.

Where found: Patangata County, North Island, N.Z.

Locality: Wainui Stream, south of Cape Turnagain.

Date: September, 1886.

Formation: Cretaceous.

Art. LI.Notes on the Hot Springs Nos. 1 and 2, Great Barrier Island, with Sketches showing the Temperature of the Waters.

[Read before the Auckland Institute, 14th June, 1886.]

Plate XXIII.

I.—On Monday, the 11th January, during the morning, I left Rosalie Bay, situated on the east of the south end of the Great Barrier, in a boat, rounded Cape Barrier, crossed Tryphena Harbour, arriving at Blind Bay in the afternoon.

From Blind Bay to the Hot Springs No. 1 there is a fairly good track, the walking being quite easy, and the surrounding country not being devoid of interest to both the botanist and geologist; but as my time was limited, and my special object was to examine the springs, I could not, though I much wished, search amongst the vast masses of volcanic rock and abundant growth of plants found skirting the heights of the White Cliffs.

Picture icon

To illustrate Paper by C. Winklemann

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When once the cliffs are mounted the track is a comparatively easy one, for the most part consisting of a gradual descent, and any hardship experienced during the first part of the journey quickly vanishes as portions of the forest are entered. Groups of fine Cyathea, Lomaria, and Pteris at once attract attention; and under the spreading leaves of the beautiful nikau (Areca sapida) the weary traveller, if he may be so termed, may rest and refresh himself, the solemn silence of the forest being alone disturbed by the melodious song of the tui (Prosthemadera novœ-zealandiœ) and the lively twitter of the little fantail (Rhipidura flabellifera), ever flitting about.

After about two hours' walk the first lot of hot springs are reached, their nearness being announced by a strong sulphurous smell, and, on reaching the place where the track cuts across the creek flowing into the Kaitoki Swamp, a sensation of warmth, and at times of oppression at the chest, is felt. This is, no doubt, caused by the accumulation of the sulphurous fumes in the valley-like locality in which the creeks and hot springs are, and is noticeable chiefly on calm days. In the early morning, and also in the evening, clouds of steam may be observed rising from the creeks, giving a very weirdlike appearance to the place.

There are two creeks, which run from two opposite directions and join at a point just below where two baths are now constructed; the water, after passing through the baths, flowing into the creek running to the Kaitoki Swamp.

The temperatures of the baths are 106° Fah. and 108° Fah., respectively, and I could obtain no deviation from these results. Various other temperatures will be found by referring to the accompanying rough sketches, all of which were carefully taken —186° Fah. being the highest, found at No. 1 spring. (See Pl. XXIII.)

The banks of the creeks, which are narrow, and turn about in all directions, are covered in most places with shrubs and ferns of several genera, including Pteris incisa, which here attains a height of 6–7 feet, Gleichenia flabellata, also the grass Paspalum scrobitulatum, and several varieties of Lycopodium, all of very luxurious growth in the vicinity of the hot water, but at some distance off assuming a more stunted appearance.

Articles of silver placed in the water of the baths turn black, thereby indicating the presence of sulphur; and the water possesses a very strong saline taste.

That the water has curative properties can, I think, be no longer doubted. The Natives on the island hold the springs as excellent for the cure of rheumatism, and several Europeans have derived benefit by a short stay in the locality, and constant bathing. There are other diseases that might be, indeed are, benefited, if not cured, by these waters. Taking the water internally acts as a mild aperient.

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In one of the creeks large deposits of red ferriferous clay are to be found, containing by analysis about 16 per cent. of iron, a specimen of which I have secured—marked “No. 1.”

II.—On leaving the first lot of springs the traveller takes the track cutting across the creek into which the water from the two baths flows, and gradually ascends a low spur. After this he descends on to a flat, and the road is very easy. Soon the fern land is lost sight of, and the forest is again entered, and in about an hour the point is reached where the second lot of thermal springs are situated.

There is nothing to mark the locality, and, as the bush is very dense, no small amount of caution is requisite, otherwise the object of search is sure to be missed. Ferns greet one on all sides—the ground is covered with them. Fungi of various kinds are noticed on the trees, and graceful festoons of Lygodium articulatum, intermixed with vines of supplejack, (Rhipogonum scandens), are in places difficult to avoid. The vegetation in this part of the forest is very rank, and will amply repay the labours of the botanist.

A small clearing is soon reached, and the dark outline of the creek in which the springs are situated is seen in the distance. A little caution is necessary in approaching, as quantities of mud will be found in the vicinity, for the most part hot, and in places steaming; and should the unwary traveller find himself knee-deep, the experience will be the reverse of pleasant.

All is quiet, save alone the sound of the water as it trickles over the stones and falls from one hole into another. Some of these holes are simply filled with muddy water; while others, and notably one of the natural baths, are full of clear hot water of a green colour. In exploring some of the many branches feeding the main creek it is necessary to take off one's boots and stockings; and in doing this no small amount of care is requisite, for in places where the water appears, and is in fact, cold, yet, on wading about, innumerable spots are found where the stones in the bed of the creek are quite hot, and where hot water is constantly coming up, though not in sufficient quantity to reach the surface. Steam rises from several holes, and on digging down a few inches almost boiling water can be obtained.

A strong sulphurous odour pervades the locality, and a good deal of silicious deposit is noticed that is not met with at the first springs. I have secured some of this deposit, which accompanies this paper, marked “No. 2.” There are two rough natural baths found at these springs, with temperatures of 124° Fah. and 116° Fah. respectively, each holding a considerable amount of water, that runs out as fast as it runs in.

The water discolours silver, and has a strong saline taste with a slight sensation of bitterness. It is, in my opinion, much stronger than that found at the first lot of springs.

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142° Fah. was the highest temperature that I here found. The Natives consider these waters to be specially useful in skin diseases, and would visit these springs in preference to the others (No. 1) on this account.

Owing to the fact of my time being limited, I was unable to further explore this locality, but I have reason to believe that within a radius of a quarter of a mile no small indications of thermal action will be found.

In closing my remarks, I must not forget to mention the discomfort that one has to contend with in the shape of our little enemy the mosquito. During the day this industrious insect is not so troublesome; but, so soon as the shades of evening draw upon the scene, these creatures assemble by the million—clouds of them, everywhere—the whole atmosphere becomes dense, and the difficulty is to find a chance to sleep during the night even for a little. I should strongly advise others to follow my example—viz., to create as many fires around the camp as possible, and, on retiring, to place quantities of smoking embers as near the blankets as convenient. In this way, and in this way alone, was I able to obtain an hour's repose. Should the smouldering embers die out, one is very quickly informed that fresh fuel is needed. It is therefore advisable to lay in a stock before going to bed.

Accompanying this paper are a few specimens of the ferns that I collected during my travels at and around the Hot Springs District. I append a few remarks anent some of them:—

Lomaria patersonii.—In great abundance; the ground covered within a radius of 50 feet from where I stood. A very pretty sight.

Schizœa dichotoma.—Very local, and scarce at that. The gum-diggers seem to be exterminating this pretty species.

Lindsaya viridis.—Very scarce, only one specimen found.

Asplenium trichomanes.—In great abundance.

Lycopodium consimilis.—Very plentiful.

Lomaria oligoneuron.—Very local.

Trichomanes tunbridgense.—Only discovered in one place, about 1,500 feet.

Several hundred specimens, and many belonging to several genera that are not represented amongst the lot I now bring forward, are still unpacked and unarranged for want of time.

In closing this paper, I cannot refrain from remarking that, with a very small expenditure, both these thermal springs might be utilized, doubtless proving of great service in curing many diseases. That they should for so long have been known, and never properly examined, is a mystery. The Natives of the Barrier have long used them medicinally with success, and there is no reason why Europeans should not do so. They are

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within easy access of Blind Bay, where a steamer calls regularly; and a good carriage road might easily be formed. As they now are, visitors can without difficulty go there, and to those who have not yet done so, I say, by all means go.

To the botanist and geologist I venture to promise an excellent field; and to the lover of nature abundance of material will be found, enough at any rate to prove the mighty workings of a strong but unseen hand.

Art. LII.On the Geology of the Trelissick or Broken River Basin,
Selwyn County.

[Read before the Philosophical Institute of Canterbury, 3rd June, 1886.]

Plates XXIV. and XXV.

Introduction.

The Trelissick Basin lies among the mountains which separate the River Rakaia from the Waimakariri, and it drains into the latter. The West Coast Road from Christchurch to Hokitika, on leaving the Canterbury Plains, does not follow up the valley of the Waimakariri, but ascends to Porter's Pass (3,097 feet), between the Thirteen-mile Bush Range and Mount Torlesse; then descending, and passing through the Trelissick Basin, it reaches the Waimakariri at an elevation of 1,808 feet above the sea. The road then ascends once more to Arthur's Pass (3,013 feet), which lies on the watershed between the east and west coasts. The ascent to Porter's Pass is rendered necessary by the deep, narrow, and almost impassable gorge, six miles in length, by which the Waimakariri reaches the plains (PL. XXV., fig. 1). In this respect the Waimakariri differs from the Rakaia and Rangitata, further to the south, which enter the plains by broad shingle valleys. In the sequel, I will offer an explanation of this remarkable peculiarity.

The first notice that I can find of the geology of the district is in the “Catalogue of the Colonial Museum,” (Wellington, 1870), in which the fossils collected by J. D. Enys, Esq., are arranged in two groups—one in the middle tertiary or Cucullæa beds, the other in the lower tertiary or Ototara series. The fossils, however, had got rather mixed, and in 1872 Dr. Hector visited and mapped the district, dividing the rocks into three formations, which he called Lower Miocene, Upper Eocene, and Cretaceo-tertiary. The fossils in the Wellington Museum, coming almost entirely from the two upper of these formations,

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were rearranged by him, and in this new arrangement they were included by me in the “Catalogue of the Tertiary Mollusca and Echinodermata of New Zealand” (Wellington, 1873).

In 1879, Mr. A. McKay examined the district for the Geological Survey, and published, in 1881, a report which is illustrated by the map and sections made by Dr. Hector in 1872.* In this report, Mr. McKay retains the three formations originally established by Dr. Hector, but makes two important alterations—(1.) He places what was formerly considered as the base of the lower miocene into the upper eocene and (2) he places the fossiliferous tuffs and volcanic rocks of White-water and Coleridge Creeks into the cretaceo-tertiary instead of the upper eocene. Dr. Hector's map appears, also, to have been altered in conformity with this view, for it does not agree with Dr. Hector's statement that the volcanic outburst took place during the upper eocene and certainly in 1873 Dr. Hector did not consider the fossils from White-water Creek to belong to the cretaceo-tertiary.

Last January I spent ten days examining the district, the result being to confirm Dr. Hector's classification of the rocks made in 1872; the later alterations of the Geological Survey being mistakes, as I hope to show presently. But I differ from Dr. Hector in his correlation of the lower limestone with the Weka Pass stone, as well as in several details of structural geology.

In the present paper I have been greatly helped by Mr. J. D. Enys, F.G.S., who showed me the localities for fossils and for eruptive rocks, and went over the fossils with me and explained my difficulties. The lists of fossils will therefore, I hope, be found tolerably accurate. They are compiled from the collections I have myself examined in the Wellington and Christchurch Museums, and in Mr. Enys' private collection. I have also availed myself as much as possible, of the list given by Mr. McKay in his report already alluded to; but in this I have had to use great caution, as it contains many errors.§ The table of distribution in many cases does not agree with the fossil locality-numbers; and these locality-numbers often do not refer to the Trelissick Basin at all. Also, some fossils appear to have got into the list by mistake. This, I think, must be the case with Fusus enysi, (McKay, MSS.), which is said to have been obtained in localities No. 231 and No. 235. The first of these localities is Ngaruroro River, Napier; the second is “Plant beds at the

[Footnote] * “Rep. Geo. Expl.,” 1879–80, p. 54.

[Footnote] † “Rep. Geo. Expl.,” 1881, p. 123; loc. No. 237 and No. 238.

[Footnote] ‡ “Rep. Geo. Expl.,” 1879–80; prog. rep., p. xxi.

[Footnote] § I was much surprised to find this, after having read the excellent lecture on accuracy that Mr. McKay gave us in his report on the Curiosity Shop beds.

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Road Cutting, Thomas River,” collected by Mr. McKay in 1874. Mr. Enys, however, assures me that he has never seen this species from here, but that he gave a specimen, which he had collected at Pareora, to Mr. McKay, distinctly telling him at the time where it came from; and it is possible that in this way the species may have got into the list.

The map accompanying this paper is reduced from the topographical survey made by Mr. Adams in 1882, which Mr. Enys supplied me with. It is, of course, more accurate than the one Dr. Hector had in 1872. The geology will, I trust, be found correct in the main; but that portion bounded by the Porter River, the West Coast Road, and the fault south of the Thomas River is purely hypothetical, the rocks here being covered by a thick deposit of gravel, which is not cut through by any stream. I was also called back to Christchurch suddenly, before I could examine the inliers of the upper limestone lying on the western edge of the basin between Thomas River and Coleridge Creek, and without having sufficiently examined the eastern slopes of Castle Hill and Flock Hill.

General Geological Structure.

The physical features of this basin have been sufficiently described by Mr. McKay. It is a rock-basin, hollowed out of a massif of sandstones, mudstones, and greywackes belonging to the Maitai System. The rocks filling the basin are divided into three distinct formations, as follows, each resting unconformably on the rocks below it:—

3. Pareora System (Lower Miocene of the survey).—A series of blue clays, shales, and sandstones, sometimes unconsolidated, with a total thickness of 600 or 700 feet.

2. Oamaru System (Upper Eocene of the survey).—Coralline limestone, underlain by volcanic grits and tuffs, passing in the south into thick scoria beds. Thickness of sedimentary rocks, 150 feet.

1. Waipara System (Cretaceo-tertiary of the survey).—Argillaceous limestone and calcareous sandstone underlain by marl, below which are green and other coloured sandstones. Maximum thickness about 1,200 or 1,300 feet.

Speaking roughly, the rocks may be said to dip everywhere towards the centre of the basin; but as the basin is much longer than broad, they form a syncline which runs from the upper part of Coleridge Creek in a N.N.E. direction, west of Castle Hill, to Parapet Rock (where the Pareora System stops)

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and Cragieburn Saddle. The north-west corner of the basin, however, is formed by another short syncline which runs nearly parallel to the first. As the West Coast Road enters the basin on its eastern side, it does not run along the syncline until after passing the Thomas River. I observed three faults in the district, but there may be others. The first crosses the Porter River just above the first limestone gorge, south of Prebble Hill,* and runs north-westerly to the north side of Castle Hill; its downthrow is to the north-east; this fault is clearly seen on the left bank of the Porter River (Pl. XXV., Section IV.). The second fault runs from Parapet Hill south-west, and crosses the Broken River at the small gorge under Sugarloaf Hill (Pl. XXV., Section II.) with a downthrow to the south-east. The third fault runs east and west along Waterfall Creek, which is the first affluent the Broken River receives from the west after entering the basin; its downthrow is to the north.

River gravels are widely spread over the basin. They form the summit of Long Spur, and are found on the ridge behind Castle Hill, at an elevation of nearly 3,000 feet above the sea. I have, however, omitted them in the sections, as I paid no particular attention to them. I saw no marks of glacier action; indeed such marks could not be expected to occur, for during the last great glacier epoch the Trelissick Basin must have been a snow-field.

The following altitudes may be found useful:—

West Coast Road Feet.
Lake Lyndon 2,743
Crossing at River Porter 2,266
Terrace N. of River Porter 2,481
Terrace S. of River Thomas 2,285
Crossing at River Thomas 2,178
Terrace at Hotel 2,371
Terrace S. of Broken River 2,390
Crossing at Broken River 2,094
Terrace N. of Broken River 2,350
Craigieburn Saddle 2,619
Lake Pearson 2,085
Hills West of the Road.
Castle Hill 3,023
Long Spur 2,747
Hog's Back 3,391
Hills East of the Road.
Prebble Hill 2,959
Gorge Hill 2,614
Flock Hill 3,269
Junction of Porter and Broken
River (estimated) 1,948
Castle Hill Station 2,520

Waipara System.

This system is largely developed on the north and east sides of the basin: a detached portion also occurs at the most southerly point, in Coleridge Creek. Its upper member is a white argillaceous limestone (Amuri limestone) generally with a platy structure, breaking up into irregular flakes, more or less parallel to the bedding. Below this comes sandstone or grit, underlain by a thick bed of marl; whilst the lower part of the system consists of grey or green sandstones, very variable in

[Footnote] * This is the same as Ram Hill in Mr. McKay's Report. The name of “Ram Hill” is not known to Mr. Enys.

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colour, and sometimes with brown coal or lignite. Its greatest elevation above the sea is at Hog's Back (3,300 feet), and Flock Hill (3,200 feet); at Prebble Hill its highest point is under 3,000 feet.

Beginning at the southern part of the basin, in Coleridge Creek, we find a small exposure of green sandstone, followed by grey marl, the thickness of which I could not estimate, but it must be more than 50 feet. These are succeeded by 200 or 300 feet of limestone, there being no appearance of the intermediate sandstone or grit. The dip is to N.E., at an angle of 50° in the lower part of the marl, gradually flattening to 28° in the limestone. Descending the creek, we lose the Waipara rocks for some distance, and then once more come across the marls underlain by green sandstone on the eastern side of the basin. The limestone is absent here, and the marls and sandstones are not well developed and rather obscure.

White-water Creek exhibits the following section (Pl. XXV., Section III.):—

9.

Limestone. A few feet only, on the left bank of the creek.

8.

Green calcareous sandstone, with fossils. 40 feet (?).

7.

Pale grey or white marl; perhaps 300 or 400 feet thick.

6.

Grey shale. 150 feet.

5.

Dark greensands.

4.

Dark soft sandstone with plant remains and efflorescences of sulphur. 40 or 50 feet thick.

3.

Impure lignite. 3 feet.

2.

Carbonaceous shales and sandstone.

1.

Grey sandstone.

The dip of beds Nos. 5 to 9 is N.W., flattening from 55° in No. 5 to 40° in the upper beds. The beds Nos. 1 to 4 dip to the N. at angles from 70° to 55°, and there may be an unconformity above them. From this point northward the upper part of the Waipara System is covered by the gravel terrace along which the West Coast Road runs, and it does not reappear until the first limestone gorge of the Porter River, near Prebble Hill, is reached. The green sandstones, however, which underlie the marl, form the banks of the Porter between Table Hill and Prebble Hill, the river running more or less on the strike; just above the first gorge these sandstones, dipping 18° N.W., end abruptly in a fault, which has a downthrow to the north (Pl. XXV., Section IV.). This appears to be a reversed fault, the older beds overlying the younger ones, but, as a gully obscures the exact line of junction, I do not feel confident that appearances can be trusted.

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The following section of the upper beds of the Waipara System is exposed in this gorge:—

6. Limestone 30 feet
5. Marl 10 "
4. Limestone 50 "
3. Calcareous grit 4 "
2. Green sandstone 40 "
1. Marl 150 "

No. 3 contains rolled fragments of volcanic rocks, and in the lower part of the marl (No. 1) there are several layers of calcareous concretions. On the south side of Prebble Hill the limestone is divided into two parts, the lower of which is composed of comminuted fragments of Bryozoa, Hydrocorallinæ, etc., forming what is called a coralline limestone, thus differing altogether from its normal character, and resembling the upper limestone, presently to be described. The dip of the upper beds just above the gorge is 40° N., increasing at the gorge to 56° N.

In the lower part of Broken River the greensands exhibit their greatest development (Pl. XXV., Section I.). I estimate their thickness here at about 850 feet, the dip being tolerably uniformly 25° W. They are covered in the Porter River by about 200 feet of grey marl, upon which rests a stratum of brownish green sandstone 20 feet thick. Then comes 20 feet of arenaceous marl, and then the limestone, about 100 feet in thickness at the second gorge. All these beds dip 25° W., but south of the Porter River the direction of the dip rapidly changes, as the beds sweep round through a right angle to the first gorge, and form Prebble Hill. I did not measure these beds in the Broken River, neither did I examine them closely in their northerly extension, although from the top of Flock Hill I saw, in the valley to the east, what I took to be a good exposure of the marl. The dip of the limestone at Flock Hill is about 25° W. (Pl. XXV., Section II.).

At Parapet Rock, on the West Coast Road, the limestone is compact and flaky, grey in colour, but weathering first red and then white. In the bed of Murderer's Creek it is underlain by about 30 feet of laminated calcareous sandstone, containing a bed of shale about 1 foot in thickness. The marl is not seen here, for to the north the greensands have been faulted upward against it. The limestone at Parapet Rock, on the right bank of Murderer's Creek, dips 77° E.S.E., but on the left bank it dips 40° S., gradually turning round to the west towards Flock Hill. The next place where I examined these rocks was at the upper gorge of the Broken River, near Sugarloaf Hill, where the same fault that occurs at Parapet Rock crosses the river (Pl. XXV., Section II.). Here the rocks have been so much disturbed by the fault that I was not able to interpret them intelligently. At the

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gorge itself the limestone dips 25° S.S.E. Immediately to the north, on the right bank of the river, white sands with rounded calcareous concretions occur, dipping 60° N.W.; while a little further up the river the limestone, apparently horizontal, is underlain directly by green sandstone with ferruginous concretions. Probably the white sands have slipped from above the green sandstone, as they occur in that position more to the west; but the locality requires further examination. Further up the river the green sandstone with concretions dips 25° W.N.W.

In Waterfall Creek, which flows into Broken River from the west, there is a very fine section. A fault goes up the bed of this creek having a downthrow to the north, and in consequence the left bank is formed of grey marl, and the right bank of green sandstone with ferruginous concretions. The exposure of the green sandstone here is about 300 feet in thickness, and on it rests white sandstone with concretions, about 100 feet, followed by another 100 feet of marl. This is followed by the limestone, which is here not less than 300 feet in thickness. The stream runs through a narrow gorge in the limestone, forming two waterfalls, and the dip is 40° W.S.W. The limestone covers a considerable amount of surface between here and the Hog's Back, forming a syncline (Pl. XXV., Section II.), with the axis lying about N. by E. and S. by W. At the north end of the Hog's Back the dip is 55° E., but more to the south the dip gets greater, until in Hog's Back Creek, at the southern end of the hill, it is nearly vertical. In Trout Creek, a small stream lying a little north of Hog's Back Creek, the eastern arm of the syncline is also highly inclined, the dip being 80° W.N.W.; so that this syncline is narrowed and steep at its southern end, while it broadens and flattens to the north.

Craigieburn Outlier.—This patch of the lower beds of the Waipara System lies outside the Trelissick Basin, from which it is separated by a low ridge of palæozoic rocks called the Craigieburn Saddle. It belongs to the valley in which Lake Pearson lies, and is 300 or 400 feet below the Craigieburn Saddle. On the left bank of the stream two seams of good brown coal are exposed. The upper of these seams is 7 ½ feet or more in thickness; the lower shows 8 feet of coal, but the bottom has not been laid bare. These coal seams are separated by a bed of brown clay 5 feet thick. The coal seams are overlain by pale soft sandstone with streaks of coaly matter, and this by a ferruginous conglomerate containing rounded pebbles of palæozoic sandstones and quartz mixed with pebbles of liparite, like those of the southern side of the Malvern Hills and the Rakaia Gorge. The dip of the coal beds is 25° N.W., and the whole series is overlain unconformably by horizontal beds of silt, which were probably deposited during the last great

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glacier epoch in a lake formed by the Waimakariri glacier blocking up the valley. The occurrence of pebbles of liparite in the conglomerate is very interesting. Similar pebbles have been noticed by Dr. von Haast in the Big Ben Coalfield on the northern side of the Thirteen-mile Bush Range,* which is about half-way between the liparites at Malvern Hills and Craigieburn; and as no rocks of the same kind are known to the west or north of Craigieburn, it seems necessary to suppose that these pebbles of liparite were brought from the Malvern Hills by a river running to the north. Now the High Peak Range, in the Malvern Hills, attains an altitude of 3,000 feet; the conglomerates at Big Ben are 2,800 feet above the sea; Lake Lyndon is 2,743 feet; Craigieburn Saddle, 2,619; and Lake Pearson 2,085 feet. So that there is, even now, sufficient fall in this direction for a river; and I shall show in the sequel that this gradient was probably steeper in the Waipara period. We are, however, met with the difficulty that the Big Ben conglomerates are, according to Dr. von Haast, surrounded by hills 4,000 to 5,000 feet high, the drainage now being from there into the Kowhai. Probably this ancient river passed over the southern flank of the Thirteen-mile Bush Range; but we must wait for more information before a complete solution of the problem can be attempted.

Fossils.—In the beds above the coal at Cragieburn I found fragments of leaves of angiospermous dicotyledons, and ferns have also been obtained from here. Both ferns and dicotyledons have been found in Murderer's Creek, about a quarter of a mile above Parapet Rock, in connection with a thin seam of coal. The greensands at the lower part of the Broken River contain quantities of a large undescribed species of oyster, apparently identical with one found near the coal at Malvern Hills. Below these oyster-beds Mr. McKay collected, in 1877, Conchothyra parasitica, together with undescribed species of Perna and Corithium; and on the south side of Prebble Hill a Tellina. From this last locality, Mr. Enys has a tooth of Myliobatis, different from those found in the Pareora rocks. The marls contain Ostrea subdentata, Hutton, on the left bank of the Porter, near its junction with the Broken River; also just above the first limestone gorge of the Porter River. According to Mr. McKay this species was collected by Dr. Hector in the greensands, but Mr. Enys knows it only from the marl. The so-called “fucoid markings” are also common in the marl at the first limestone gorge, as well as scales of Teleost fish.

[Footnote] * “Rep. Geo. Expl.,” 1871–72, p. 21.

[Footnote] † Potamogeton ovatus, figured in the “Catalogue of Geological Exhibits, Indian and Colonial Exhibition,” p. 61, probably came from here.

[Footnote] ‡ Perhaps the same as O. alabamamensis, Lea, from the Eocene of Alabama.

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Dr. Hector and Mr. McKay also mention Pecten zittelli (called P. pleuronectes) from the marl, but Mr. Enys has never seen this species in the Trelissick Basin, and it is not included in Mr. McKay's list of fossils at the end of his report.

In the sandy beds above the marl in White-water Creek, I noticed the cast of a Flabellum (?) and another of Cardita, (apparently C. patagonica). In his report Mr. McKay says that Pecten hutchinsoni comes from these beds at the first gorge of the Porter; but in the list of fossils at the end of the report it is said to have come from what he supposed to be the same beds in White-water Creek, but which I shall presently show belong to a higher horizon. I searched in vain for fossils in these beds at the first gorge of the Porter, and consequently I suppose that it is Mr. McKay's list and not his report that is correct. In the limestone at Coleridge Creek I noticed a Waldheimia (?), spines of an echinoderm, and a net-coral (Retepora).

Correlation of the Beds.—That these rocks belong to the Waipara System is admitted by all geologists, and the sequence is very like that at the Waipara.

Waipara, after Dr. von Haast.*
Feet.
9. Grey marl (Amuri limestone) 60–100
8. Sandy clays 60–100
7. Greensand 80–100
6. Blue marl 50–70
5. Calcareous greensand 80–100
4. Concretionary sandstone, with Plesiosaurus, etc. 200
3. Soft sandstone, with Ostrea and Conchothyra 70–150
2. } Sandstone and lignite, with
1. } leaves of Dicotyledons 30–60
Trelissick Basin.
Feet.
} Argillaceous limestone
(Amuri limestone) 100–300
Greensands 50
Grey marl 50–300
White sandstone 20–100
Green sandstone, with concretions and Myliobatis
Sandstones, with Ostrea and Conchothyra
Sandstone and lignite, with leaves of Dicotyledons } 300–850

In mineral characters the Amuri limestone at Waipara and Weka Pass closely resembles the limestone which forms the upper member of the system in Trelissick Basin, and I have elsewhere shown that in the Weka Pass District the Amuri limestone is the upper member of the Waipara System; so that, stratigraphically and lithologically, they appear to be the same. Both are equally destitute of fossils. The officers of the Geological Survey correlate this limestone with the Weka Pass stone, but I cannot see on what evidence they rely. Certainly it does not contain any of the fossils characteristic of the Weka Pass stone, which are similar to those of the Curiosity Shop beds,

[Footnote] * “Rep. Geol. Expl.,” 1870–71, p. 9.

[Footnote] † Quar. Jour. Geol. Soc. of London, vol. xli., p. 266.

[Footnote] ‡ Quar. Jour. Geol. Soc. of London, vol. xli., p.

Picture icon

Geological Map of the Trelissic Basin

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and these are represented in the Trelissick Basin by the upper limestone which forms Castle Hill.

The correlation of the Waipara System with any European equivalent at present presents considerable difficulties. The occurrence of Plesiosaurus above beds containing leaves of dicotyledonous angiosperms would seem to indicate an upper cretaceous age; but Myliobatis (which is here thought to be on the same horizon as Plesiosaurus) has never yet been found in the Northern Hemisphere in any mesozoic rock. I have often protested against the cretaceo-tertiary formation as defined by the Geological Survey; but this has been, not because I deny the possibility of the Waipara period extending into the tertiary era, but because I deny that the limestones, etc., of Weka Pass, Ototara, and other places belong to the Waipara System.

Oamaru System.

Sedimentary Rocks.—These rocks attain their greatest elevation at Flock Hill (3,269 feet). At Castle Hill they go to 3,023 feet, and at Prebble Hill to 2,959 feet.

In the upper part of Coleridge Creek, tuffs, covered by limestone, rest on the rocks of the Waipara System, and dip 55° N.N.W. To the west an apparently isolated portion of the limestone requires further examination, as it appears to rest on Pareora beds; but probably this is deceptive. To the eastward the beds curve round to the north, and the limestone rests on the palæozoic rocks; they then again cross the creek, dipping at a high angle to the west. This is a famous locality for fossils, the tuffs under the limestone containing numerous teeth of Lamna, Carcharodon, and Sparnodus. On the north side of the creek the limestone is absent, the Pareora rocks resting on the tuffs. In White-water Creek the limestone is about 40 feet thick, and dips 15° W.S.W. It is underlain by a bed of conglomerate, formed of rounded fragments of volcanic rocks and limestone in a calcareous cement, which is full of fossils; below it comes dark-green tufaceous sandstone. The limestone can be followed continuously from here northward to Castle Hill, where it is cut off by the fault already mentioned. Between White-water Creek and Castle Hill the dip is 8° W. to 12° W. At Castle Hill it is 25° W.N.W., and near the fault 32° N. The eastern slope of Castle Hill I did not examine sufficiently; possibly the Waipara System may form the lower part. The limestone at Castle Hill is not less than 100 feet thick.

The Oamaru System again appears on the north side of the first limestone gorge of the Porter River, dipping 33° N.W. The greensands are here about 40 feet thick, but the limestone is very poorly developed, having been largely denuded before the deposition of the Pareora System. At the junction of the Thomas River with the Porter the limestone is about 50 feet

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thick, and is underlain by 10 feet of volcanic grit, below which comes 40 feet of tufaceous greensands, much current-bedded, and known as the “Fan coral-beds,” from the occurrence of Flabellum laticostatum, Ten.-Woods. These rocks pass in an easterly direction up Prebble Hill, but they are not connected with those at the first gorge of the Porter. In Home Creek the limestone is 60 or 70 feet thick, and the tufaceous greensands 50 feet, with a bed of blue clay, 1 ½ feet thick, between them and the limestone. The dip in the Thomas River is 20° W. to 25° W., in the Home Creek about 20° W.S.W., and at the natural tunnel through which Murderer's Creek joins Broken River the dip is 10° N.W. In Broken River the tufaceous beds are thinner, but I did not examine them closely. At the natural tunnel they have passed into a calcareous tuff, which I did not recognize further north. An outlier of limestone occurs on Flock Hill, and two inliers on the west margin of the basin: one near the head of Moth Creek, the other a little north of the White-water Creek; but I did not examine them.

Volcanic Rocks.—Scoria beds and tuffs are largely developed in Coleridge and White-water Creeks. In Coleridge Creek some of the scoria beds might almost be called agglomerates, and evidently we are here near the orifice of a volcano which was in eruption during the early part of the Oamaru period. Some of the tuffs are fine-grained, compact rocks of a blue-black colour, and when broken present a sparkling crystalline surface, so that they might, at first sight, be readily mistaken for lava streams. But they effervesce with acid, and when thin slices are examined with a microscope they are found to consist of fragments of a deep brown-yellow palagonite, held together by a crystalline calcareous cement; some of the larger fragments contain crystals of olivine, and occasionally there are separate olivine fragments. Other tuffs are finer in grain, and effervesce very slightly. The specific gravity of these tuffs varies from 2.10 to 2.70, according to the amount of calcite they contain. In Whitewater Creek, just above the Amuri limestone, there is a tachylyte lava stream. It is compact, black, dull, breaks up irregularly under the hammer, and has a bluish tinge on the surface of the joints. Its specific gravity is 2.20. Under the microscope, in very thin slices, it is seen to be a vesicular tachylyte of an olive-brown colour, studded with globulites arranged in groups, either as clouds or as blackish spots.

In Home Creek, resting upon the Amuri limestone, another similar palagonite tuff occurs, compact, and of a blackish-green colour. This bed is 8–10 feet thick; the lower part is granular, effervesces freely, and has a specific gravity of 2.10; the upper part is finer in grain and effervesces slightly, its specific gravity is 2.00. Under the microscope this tuff is seen to be composed of angular fragments of brownish-yellow, or yellowish-green,

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vesicular palagonite in a calcareous cement. Olivine is rare, but there are occasionally small angular grains of quartz mixed with the palagonite. In the finer upper portion the palagonite fragments are smaller and greener, and there is less calcite. All these rocks break up into irregular cuboidal masses when struck by the hammer.

Dykes.—Eight dykes are known in the basin, all but one being clustered round Prebble Hill. Beginning in the south, we find the first (A) on both sides of the Porter River, near Table Hill (palæozoic), running east and west; I could not ascertain its thickness. The second (B) is just south of the fault at the first limestone gorge; it is nearly vertical, and runs W.N.W. through the greensands of the Waipara System. Turning eastward, along the south side of Prebble Hill, the next dyke (C) forms the crest of a long spur which runs W.N.W. The fourth (D) is on the ridge forming the watershed of the Broken River; it also runs W.N.W. The fifth (E) crosses Broken River; it is nearly vertical, runs N.N.E., and is 15 feet thick. Going up the river, the sixth dyke (F) is on the north bank, and runs N.N.E. The seventh (G) is also on the north bank of the Broken River, but above its junction with the Porter; it is 12 feet thick and runs N.W. The eighth dyke (H) is on the north bank of the Porter, in the marl; a small fragment, 12 feet long by 8 broad, is all that is exposed: it runs N.W. None of these dykes can be traced higher than the greensands, except H, and this one does not penetrate to the top of the marl. They are all dark bluish-black in colour, and are all composed of a microcrystalline ground-mass of laths of plagioclase, rounded grains of pale-green augite and magnetite; but they can be divided into two groups. Dykes A, C, D, E, and H are basalt, with a specific gravity ranging between 2.82 and 2.95, the mean being 2.87. They vary from finely granular to crypto-crystalline. They all contain olivine, more or less abundantly, in rounded or broken crystals. This olivine is of two kinds: one is pale green, and shows brilliant colours with polarised light; the other is colourless, and when revolved between crossed nicols, either merely passes through grey into black, or else changes from pale bluish-green to pinkish purple. Dykes B, F, and G are augite andesite, with a specific gravity ranging between 2.59 and 2.70, the mean being 2.64, They contain no olivine, and have a finely granular texture. The position of these dykes, clustered round Prebble Hill and penetrating the green sandstones only, gives the impression, at first sight, that they may have been connected with a small volcano under Prebble Hill, and that they were formed before the marl and limestone were deposited. But there are no traces of contemporaneous volcanic action in the green sandstones, nor in the marl, while only one of the dykes has penetrated so far upward as the lower part of

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the marl. Between the marl and the limestone rolled volcanic pebbles are found, but these may have come from the same source as the liparite pebbles found at Craigieburn, which were certainly not erupted in the neighbourhood. Chemically these dykes appear to be closely allied to the tachylyte and palagonite tuffs of White-water and Home Creeks; so that we may, I think, conclude that they were erupted at the commencement of the Oamaru period, and that their failure to penetrate Prebble Hill was owing to the tough nature of the overlying rocks.*

I have considered that the tufaceous beds in White-water Creek are of the same age as those at the Thomas River and Home Creek, where they join the Porter; but as Mr. McKay holds a different opinion, it is necessary to state the evidence more fully:—(1.) Stratigraphically, the positions of the two are identical. Mr. McKay, unfortunately, missed seeing the out-crop of the Amuri limestone on the left bank of White-water Creek, which is now quite plain, although it might have been covered up at the time of his visit. (2.) Lithologically, the palagonite tuffs are the same in both places, and are quite different to the beds between the marl and the Amuri limestone, at the first gorge of the Porter, with which Mr. McKay would compare them. (3.) Palæontologically, the fossils from the two localities are identical. If the reader will compare the list of fossils given by Mr. McKay from the tuffs at White-water Creek (locality No. 241) with those from the Fan coral-beds at Thomas River (localities Nos. 239 and 243), he will find that there are in the first list 23 named species, (the undetermined species not being available for comparison), all but three of which occur in the Fan coral-beds. And of these three, Triton minimus (= T. pseudospengleri, Tate) occurs elsewhere in New Zealand, only in the Pareora rocks; Calyptra maculata (= Trochita neozelanica, Lesson) is still living; and Pecten hectori (= P. yahlensis, Ten.-Woods) is a miocene shell of Victoria and South Australia. Consequently, none of these can indicate a greater age for the White-water Creek beds. Mr. McKay says: “The fossils collected from these beds at the first limestone gorge on the Porter River were too few to serve the purpose of this comparison; yet, as far as these may, they tend to show that those from White-water Creek belong to the lower tufas at present under consideration. The comparative list at the end of this report will show upon what grounds this opinion rests.” The locality

[Footnote] * Since the above was written, Mr. Enys has brought me a specimen from another dyke on the south-west side of Prebble Hill, between dykes c and d. I have called it dyke k. Its specific gravity is 2.81, and no doubt it is a basalt; but I have not made a microscopical examination. It runs nearly north and south, and may be a continuation of dyke e, which has, however, a specific gravity of 2.92.

[Footnote] † “Reps. Geo. Expl.,” 1879–80, p. 64.

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here mentioned is “No. 240, below Weka Pass stone, Porter River;”* but on looking over his list for the fossils collected here I was surprised to find that none are recorded. (4.) Also, if the large development of tuffs and scoria in Coleridge Creek belonged to the Waipara System, there would certainly be some indications of them in the upper part of the creek, between the lower limestone and the marl, which is not the case.

Fossils.—The following is a list of all the fossils I know from these beds:—

(1.) From the limestone—

Pecten hochstetteri, Zittel; and Waldheimia triangularis, Hutton. Both from the quarry at Castle Hill.

(2.) From the tuffs and greensands—

1.

Cylichna enysi, Hutton.

2.

Marginella dubia, Hutton.

3.

Marginella ventricosa, Hutton.

4.

Voluta elongata, Swainson.

5.

Voluta attenuata, Hutton.

6.

Mitra enysi, Hutton.

7.

Ancillaria hebera, Hutton.

8.

Triton pseudospengleri, Tate.

9.

Natica ovata, Hutton.

10.

Natica hamiltoni, Tate.

11.

Trochita neozelanica, Lesson.

12.

Crepidula striata, Hutton.

13.

Turritella ambulacrum, Sowb.

14.

Trochus nodosus, Hutton.

15.

Zizyphinus spectabilis (?), Adams.

16.

Cantharidus tenebrosus (?), Adams.

17.

Teredo heaphyi, Zittel.

18.

Panopœa orbita, Hutton.

19.

Panopœa worthingtoni, Hutton.

20.

Pholadomya neozelanica, Hutton.

21.

Paphia attenuata, Hutton.

22.

Cardium patulum, Hutton.

23.

Cardium serum., Hutton.

24.

Lucina dentata, Wood.

25.

Cardita patagonica, Sowb.

26.

Crassatella attenuata, Hutton.

27.

Arca decussata, Sowb.

28.

Limopsis aurita, Brocchi.

[Footnote] * “Rep. Geo. Expl.,” 1881, p. 123.

[Footnote] † Mr. Enys informs me that a very large shark's tooth—probably Carcharodon angustidens—has also been found here; but he has not been able to secure it.

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29.

Mytilus striatus, Hutton.

30.

Crenella elongata, Hutton.

31.

Lima jeffreysiana, Tate.

32.

Pecten hutchinsoni, Hutton.

33.

Pecten athleta, Zittel.

34.

Pecten yahlensis, Ten.-Woods.

35.

Pecten chathamensis, Hutton.

36.

Pecten polymorphoides, Zittel.

37.

Terebratula bulbosa, Tate.

38.

Waldheimia gravida, Suess.

39.

Waldheimia taylori, Etheridge.

40.

Waldheimia patagonica, Sowb.

41.

Waldheimia radiata, Hutton.*

42.

Terebratella sinuata, Hutton.

43.

Terebratella aldingœ, Tate.

44.

Terebratellina suessi, Hutton.

45.

Rhynchonella nigricans, Sowb.

46.

Rhynchonella squamosa, Hutton.

47.

Leiocidaris australiœ, Duncan.

48.

Echinus woodsii, Laube.

49.

Pericosmus compressus, McCoy.

50.

Brissus eximius, Zittel.

51.

Flabellum laticostatum, Ten.-Woods.

52.

Flabellum spenodeum, Ten.-Woods.

Of the 46 species of Mollusca here enumerated, ten have not been found elsewhere, nine have been found elsewhere only in the Pareora System, and six elsewhere only in the Oamaru System. But as the known Pareora species are more than two and a half times as numerous as the known Oamaru species, this leaves a balance in favour of the beds belonging to the Oamaru System. The four Echinoidea belong only to the Oamaru System. Flabellum laticostatum is not recorded from elsewhere, but F. sphenodeum occurs also at Mount Caverhill, in the Amuri District. Five or six species of the Mollusca are still living, that is about 10 per cent. I therefore agree with the Survey that these beds are the equivalents of the Curiosity Shop beds, which I have elsewhere shown to be the equivalents of the Weka Pass and Ototara limestones.

Relation to the Waipara System.—At the first limestone gorge of the Porter River, the Oamaru System is seen resting on the Waipara System quite unconformably, as has already been

[Footnote] * Waldheimia radiata, sp. nov. Shell broadly ovate, with a deep ventral ridge and dorsal furrow, but very irregular. Surface with strong longitudinal ribs—about 18 on the ventral valve, of which 4 or 5 are on the ridge—imbricated with coarse growth-lines. Beak prominent, acute, the foramen sub-triangular, the deltidial plates disunited. Length, 0.56; breadth, 0.5; thickness, 0.3 to 0.4 inch. A well-marked punctate shell.

[Footnote] † “Quar. Jour. Geol. Soc. of London,” vol. xli., p. 547.

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pointed out by Mr. McKay. At White-water Creek the Amuri limestone had been denuded down to a few feet before the Oamaru System was deposited; and in the lower part of Coleridge Creek the Oamaru System rests on the marl, the Amuri limestone having been entirely removed, although it still retains a thickness of between 200 and 300 feet at each end of the basin. In the upper part of Coleridge Creek an unconformity can also be made out, the Waipara System striking N.W., and the Oamaru System, in contact with it, W.S.W. The unconformity is therefore well marked.

Pareora System.

This system rests on palæozoic rocks along the west margin of the basin, and extends eastward to the Oamaru System. More to the north it rests on the Waipara System. It attains its greatest elevation (3,390 feet) at the Hog's Back, while in the southern part of the basin it does not reach to 3,000 feet.

The following is the section, in descending order, seen in an affluent of White-water Creek from the north. (Pl. XXV., Section III.)

Feet.
7. Blue shales (plant beds) 150
6. Soft grey sandstone, current-bedded 200
5. Grey sandstone, or sand, with layers of broken shells, Struthiolaria spinosa, etc. 80
4. Sandy clay full of Lamellibranchs 2
3. Grey sandstone, with shells and concretionary layers 15
2. Sandy clay, full of Lamellibranchs 3
1. Grey calcareous sandstone, with shells 15

No. 1 rests upon the denuded surface of the limestone of the Oamaru System (Weka Pass stone), which dips 15° W.S.W., while the Pareora System dips 10° W.N.W. Further up the creek the dip of the Pareora System remains the same in direction, but increases to 25° in No. 7.

In Moth Creek the beds are obscure, but they consist of blue sandy clays with marine shells, probably representing No. 6 of the White-water Creek section. In the Thomas River, from the road crossing downwards, the following are seen:—

6.

Dark grey clay and shales, with plant remains.

5.

Pale grey-yellowish sands, and thin seams of shale, with plants.

4.

Grey sandy clays and shale.

3.

Lignite.

2.

Grey sandstone, full of Lamellibranchs.

1.

Grey sandstone, current-bedded—200 feet.

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The lower beds dip 23° N.W., but higher up the river they appear to be horizontal (Pl. XXV., Section I.), although much disturbed by slips. The plant beds on the right bank of the river, near the road, dip 65° N.N.W. This high dip is probably due to the fault which has thrown the beds down. On the right bank of the Broken River, where the road crosses, the following section is seen, the rocks dipping 12° S.W.:—

5.

Brown and blue shales.

4.

Grey sand.

3.

Lignite, 2 ½ feet.

2.

Clay, 3 or 4 feet.

1.

Sands, current-bedded.

The sandy beds with Struthiolaria spinosa, etc., were not seen by me in the Thomas River section, although they are well-developed in the Porter River between the two gorges; it is possible, therefore, that an unconformity may occur below the lignite. However, the lignite is found in the Porter River, between the two gorges, overlying the Struthiolaria beds, and I could see no evidence of unconformity; but the beds are disturbed and the sections obscure.

An outlier occurs on the Hog's Back, in the north-west corner of the basin, where the beds, resting unconformably on the Waipara System, dip 15° W.S.W. (Pl. XXV., fig. 2).

Relation to Oamaru System.—In White-water Creek I have already mentioned that the Pareora System is unconformable to the Oamaru System; on the north side of Coleridge Creek the Pareora rocks rest on the tufaceous beds of the Oamaru System the limestone having been entirely denuded away, and in the north part of the basin it rests on the Waipara System. In fact, the unconformity between the Pareora and Oamaru Systems is manifest, and admitted by all. Mr. McKay, however, takes the beds lying on the upper limestone, at the junction of the Thomas with the Porter, as the upper part of the Oamaru System, his reason being that boring molluscs have penetrated some of the shells after the matrix with which they are filled had consolidated, proving unconformity with the upper beds (i.e., p. 68). But this is not a good reason, as the same thing may be seen in many consolidated beaches at the present day; and as these particular rocks are very calcareous, they probably consolidated as fast as they were formed. The locality is very difficult, indeed dangerous, to get at, and the stratigraphical relations of the rocks cannot be easily examined; but the fossils (localities Nos. 237 and 238 of the Survey) are entirely Pareora, and I therefore include them in that system, as was done by Dr. Hector in 1872.

Fossils.—As the fossils have been collected from two different horizons, it is better to keep them distinct. The lower horizon

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includes 1 to 4 of the White-water Creek section, and 1 to 2 of the Thomas River section. The upper horizon includes the beds between these and the lignite or plant beds.

Lower Horizon.

1.

Cominella carinata, Hutton.

2.

Voluta Kirkii, Hutton.

3.

Triton pseudospengleri, Tate.

4.

Crepidula monoxyla, Lesson.

5.

Crepidula costata, Quoy and Gaim.

6.

Turritella gigantean, Hutton.

7.

Turritella rosea, Quoy and Gaim.

8.

Vermetus moniliferus, Hutton.

9.

Turbo superbus, Zittel.

10.

Dentalium giganteum, Sowb.

11.

Venus oblonga, Hanley.

12.

Venus yatei, Gray.

13.

Cytherea assimilis, Hutton.

14.

Dosinia magna, Hutton.

15.

Dosinia subrosea, Gray.

16.

Tapes curta, Huton.

17.

Cardium spatiosum, Hutton.

18.

Crassatella ampla, Zittel.

19.

Arca decussate, Sowb.

20.

Cucullaa ponderosa, Hutton.

21.

Cucullaa worthingtoni, Hutton.

22.

Cucullaa alta, Sowb.

23.

Pectunculus laticostatus, Quoy and Gaim.

24.

Pectunculus globosus, Hutton.

25.

Pectunculus cordatus, Hutton.

26.

Modiola australis, Gray.

27.

Lima crassa, Hutton.

28.

Hinnites trailli, Hutton.

29.

Rhynchonella nigricans, Sowb.

Upper Horizon.

1.

Stenorhynchus (?), caudal vertebra.

2.

Myliobatis, teeth.

3.

Purpura tetiliosa, Lamarck.

4.

Siphonalia mandarina, Duclos.

5.

Cominella carinata, Hutton.

6.

Cominella maculate, Martyn.

7.

Oliva neozelanica, Hutton.

8.

Ancillaria australis, Sowb.

9.

Voluta pacifica, Solander.

10.

Voluta gracilis, Swainson.

11.

Voluta kirkii, Hutton.

12.

Conus trailli, Hutton.

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13.

Pleurotoma sulcata, Hutton.

14.

Clathurella hamiltoni, Hutton.

15.

Natica darwinii, Hutton.

16.

Natica gibbosa, Hutton.

17.

Natica ovata, Hutton.

18.

Natica hamiltoni, Tate.

19.

Cerithium nodosum, Hutton.

20.

Struthiolaria spinosa, Hutton.

21.

Struthiolaria obesa, Hutton.

22.

Struthiolaria cingulata, Zittel.

23.

Trochita neozelanica, Lesson.

24.

Crepidula incurva, Zittel.

25.

Turritella tricincta, Hutton.

26.

Turbo superbus, Zittel.

27.

Cantharidus tenebrosus, Adams.

28.

Dentalium conicum, Hutton.

29.

Mactra discors, Gray.

30.

Cytherea enysii, Hutton.

31.

Cytherea assimilis, Hutton.

32.

Chamostrœa albida, Lamarck.

33.

Crassatella ampla, Zittel.

34.

Cardita patagonica, Sowb.

35.

Pectunculus laticostatus, Quoy and Gaim.

36.

Mytilus latus, Chemnitz.

37.

Perna, sp. ind.

38.

Anomia undata, Hutton.

In the plant-beds, above the lignite, casts of two small bivalves have been obtained. They have been referred doubtfully to Unio, but they are much smaller than any species known to me, and one of them appears to have been radiately ribbed; they have the shape of Callista.

Origin of the Trelissick Basin.

Mr. McKay appears to be of opinion that the form of this basin is due, in large part, to foldings of the rocks by compression, subsequent to the deposition of the Pareora System; and it is to these foldings that he would attribute the upheaval of the surrounding mountains.* This opinion is, perhaps, to some extent, due to the very exaggerated sections which accompany his report; but in reality there is no dip in either the Pareora or the Oamaru rocks which cannot be easily accounted for (1) by original deposition; or (2) as the effect of subsequent landslips or faults; or else (3) by being in the immediate neighbourhood of a volcano. The only localities where the dip is more than 30° are in Coleridge Creek, near the volcano; in the upper gorge of the Porter; and the plant beds at the Thomas where the road

[Footnote] * “Rep. Geol. Expl.,” 1879–80, p. 59.

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crosses, close to faults; or else in places where landslips have evidently taken place. There is no stratigraphical evidence of folding by lateral pressure of a general character, involving the palæozoic rocks; and if the tertiary rocks had been folded by compression they would have been to some extent altered by the heat and pressure, as are, the eocene and miocene rocks of the Swiss Alps and the Himalaya. Here, however, the tertiary rocks are quite like their equivalents on the plains and at Oamaru.

With the Waipara System some folding may have occurred, but I think the evidence is not much in favour of it. The steep dips at Parapet Rock and in the Broken River near Sugarloaf are no doubt due to the fault which crosses at both places. In the lower part of Whitewater Creek we find dips varying from 45° to 70°, but these may be owing to subsidence of the volcano which burst through them in the Oamaru period. At the Hog's Back true folding may have occurred; although even here the steep syncline at the south end may have been formed in connection with the fault; indeed, it looks much as if it had been squeezed together between two faults (Pl. XXV., fig. 2). But this movement, whatever may have been its cause, took place before the deposition of the Pareora System, which rests at a slight angle, upon the upturned edges of the Amuri limestone.

The valley in which the Trelissick Basin lies evidently owes its origin to a pre-cretaceous river, which ran in a northerly direction from Coleridge Creek to Craigieburn, and joined the Waimakariri. But the question arises: Was the present rockbasin, in which the Waipara and younger rocks lie, hollowed out by a glacier? Or is it due to unequal movements of lava? I was formerly of opinion that it had been hollowed out by a pre-tertiary glacier coming from the Waimakariri and emptying down the Acheron into the Rakaia; but I have now abandoned this idea, partly because of the great fall between Craigieburn Saddle and Lake Pearson, but chiefly on account of the discovery of pebbles of liparite at Craigieburn, which could hardly have been brought from the Malvern Hills if a lake had lain in the way. It now seems to me more probable that the northern part of the valley was elevated more than the southern part, during the elevation that followed the deposition of the Pareora marine strata; for such an unequal elevation would account for all three rock systems being now found at higher elevations in the northern than in the southern end of the basin, notwithstanding the northerly downthrow of two of the faults. This greater elevation of the northern or lower part of the valley would throw the drainage of the basin over the low eastern rim, and the present gorge of the Broken River would then be cut. This would have occurred during, or after, the last great glacier

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epoch. This same unequal elevation would also account for the narrow gorge, already mentioned, by which the Waimakariri enters the Canterbury Plains, and which, according to Dr. von Haast, has been entirely cut since the glacier epoch.* If this hypothesis be correct, it follows that the inland sea in which the Waipara, Oamaru, and Pareora rocks were deposited, must have entered the Trelissick Valley from the Waimakariri by Craigieburn; the Broken River gorge not having been cut until long afterwards; and as all these rock systems bear marks of an epoch of subaërial denudation following that of their deposition, it follows that the sea entered by this channel at three different times, each time followed by an epoch of upheaval.

[Addendum.]

Christchurch, 30th September, 1886.

Mr. J. D. Enys has informed me that, since my visit to Castle Hill Station, he has discovered a dyke nearly at the top of Gorge Hill—between Broken River and the Porter—which he believes to be a continuation of dyke D. This furnishes absolute proof that one of the dykes, at any rate, is younger than the Waipara System; and probably, therefore, all are younger.

F. W. H.

Art. LIII.—On the so-called Gabbro of Dun Mountain.

[Read before the Philosophical Institute of Canterbury, 4th November, 1886.]

This is a very coarsely-crystalline rock composed of two minerals only. One is a foliated greenish-brown mineral, like bronzite or diallage, in irregular crystalline masses. The other is an opaque-white or greenish-white felspar, like saussurite. The specimen was given to me by Sir J. von Haast, and I do not know its field relations further than that it comes from the Dun Mountain, near Nelson. Its specific gravity is 3.15.

The foliated mineral.—Under the lens the principal cleavage planes are seen to be finely striated; this striation being due to the development of a second plane of cleavage, less perfect than the first, and crossing it at an angle of about 67°. In thin sections, showing both cleavages, the mineral gives brilliant polarization colours, and always extinguishes parallel to the fine striations and oblique to the principal cleavage. This shows

[Footnote] * “Geology of Canterbury and Westland,” p. 213.

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that these sections must be transverse to the principal axis; for if not, the cleavages would either be at right angles to each other (Rhombic System, or Ortho-pinacoid), or else the extinction would be oblique to both cleavages (Clino-pinacoid). The edge formed by these cleavage faces is therefore parallel to the principal axis, and as the principal cleavage is not on an axis of elasticity, it must be parallel to one face of the prism: no cleavage seems to be developed parallel to the other face.

A section, approximately at right angles to the principal axis—as proved by the angle between the cleavages—shows, with convergent polarized light, a symmetrical bisectrix with wide axial angle, and the axial plane in the direction of the striations. Cleavage flakes from the principal cleavage (210) give straight extinction, and show an optic axis on the margin of the field, with the axial plane in the direction of the striations; thus giving a further proof that this cleavage is parallel to the face of the prism.

Cleavage flakes of the second cleavage show no striations, but extinguish apparently parallel to the first cleavage; this, however, is not very exactly marked. They show no interference figure with convergent polarized light.

These straight extinctions, and the bisectrix seen on 001, prove that the mineral belongs to the Rhombic System. Now, in the Rhombic System, the angle between 110 and 100 must lie between 0° and 45°, while the angle between 110 and 010 must lie between 45° and 90°. Consequently, as in our case the angle between the two cleavages is about 67°, it follows that the second cleavage, and the plane of the optic axes, are parallel to the brachy-pinacoid.

The angles of the prism will be 134° and 46°, but the measurements are not very exact, owing to the want of proper instruments; they are however sufficiently so to show that the mineral is not a rhombic pyroxene but a rhombic amphibole, and probably, therefore, anthophyllite. Pleochroism is well marked in sections more or less parallel to 001. The colour for a being greenish-yellow, and for β reddish-brown. Sections parallel to the cleavages do not show any marked pleochroism, so that the colour for γ is greenish-yellow, like that for a. Before the blow-pipe the mineral is infusible, or fusible only with great difficulty. All these characters agree with anthophyllite, but the typical form of that mineral is said by E. S. Dana to have its principal cleavage parallel to 100, and the relative lengths of the lateral axes are not so unequal as in our variety.

The felspar.—This mineral is so much altered as to show merely a number of granules and rods in a transparent base, which is generally quite amorphous, but occasionally crypto-crystalline. No doubt it is some kind of plagioclase, but

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whether it has been anorthite or labradorite can only be determined by chemical analysis; at present it is saussurite.

The question now arises, What name are we to give the rock? There is no special name applied to plagioclase-antho-phyllite rocks—apparently because anthophyllite is rare. But as anthophyllite is a rhombic amphibole, it may be grouped with hornblende; so that perhaps the name corsite might be made to include our rock. The typical corsite—i.e., the orbicular diorite of Corsica—is said by Cotta to be composed of anorthite, blackish-green horn-blende, and some quartz. Later writers have omitted the quartz as undoubtedly of secondary origin, and corsite is now defined as an anorthite-hornblende rock. The hornblende is generally the foliated variety called smaragdite, and is supposed to be a decomposition product of augite; so that, from this point of view, a corsite would be an altered eucrite or gabbro, and in the latter case could hardly be distinguished from euphotide, as restricted by Professor Bonney. Mr. Teall looks upon corsite as a variety of diorite in which the felspar is anorthite.*

Now, although hornblende is undoubtedly often a secondary product after augite, we cannot suppose that all hornblende has been thus derived; that all syenites have been augite syenites, and that all diorites have been gabbros or dolerites. Evidently hornblende is often an original constituent of a rock, and therefore, under certain conditions, we have no reason to suppose that it may not become schillerised as augite does; smaragdite answering to diallage, and anthophyllite to bronzite or hypersthene. This being so, it would seem to be advisable to have a name to represent this particular condition of amphibole rocks, and I would suggest that the name corsite be enlarged to include all rocks essentially composed of plagioclase and a foliated amphibole (such as smaragdite and anthophyllite); it would then bear the same relation to diorite that gabbro and norite do to dolerite. With the pyroxene rocks the kind of felspar is not always taken to warrant a separate name, as shown by norite, which is a plagioclase-enstatite rock; and gabbro is often made to include eucrite. Why, therefore, should the amphibole rocks be treated differently to the pyroxene rocks? In the rock from the Dun Mountain, there is nothing to indicate that the anthophyllite is a changed pyroxene, but it is itself altered in places into a green fibrous mineral which may be smaragdite.

[Footnote] *British Petrography,” p. 73, footnote.

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Art. LIV.On the Geology of the Country between Oamaru and Moëraki.

[Read before the Philosophical Institute of Canterbury, 16th July, 1886.]

Plate XXVI.

Introduction.

The Hon. W. Mantell was the first geological observer in this district. In 1850 he described the Ototara limestone of Oamaru, the Onekakara clay of Hampden, and the volcanic ash of Kakanui. The fossils collected by him were examined by Dr. Mantell, Professor Morris, and Professor Rupert Jones. The Ototara limestone was referred, with doubt, to either the cretaceous or the eocene period; while the Onekakara clay was considered to be either pleistocene or newer tertiary; but, at this time, it must be remembered, the recent fauna of the New Zealand coasts was very imperfectly known. Mr. Mantell remarks that he had no opportunity of ascertaining the relative positions of the Ototara limestone and the volcanic ash of Kakanui.*

In 1865, Dr. Hector placed the Moëraki series (including the Onekakara clay) below the Oamaru series, and considered both to be miocene; the volcanic rocks he considered to be pliocene.

In 1869, Mr. C. Traill, after examining the fossils from Hampden and Awamoa, came to the conclusion that both were probably miocene.

In 1870, Dr. Hector placed the Hampden and Awamoa beds in his Upper, or Struthiolaria series, and the Oamaru limestone (including the Hutchinson's Quarry beds) in his Older, or Ototara series.§

In my “Catalogue of the Tertiary Mollusca and Echinodermata of New Zealand” (1873), as also in my “Report on the Geology of Otago” (1875), I followed Dr. Hector, but called his upper and his older series the Pareora and Oamaru formations respectively. In this latter report I also pointed out that the volcanic rocks of Moëraki overlie the Onekakara clay, thus belonging to a later period of volcanic activity than those supposed to be associated with the Hutchinson's Quarry beds at Oamaru.

In December, 1876, and January, 1877, Mr. A. McKay examined the district, and made several important alterations.

[Footnote] * “Quar. Jour. Geol. Soc. of London,” vol. vi., p. 324.

[Footnote] † “Quar. Jour. Geol. Soc. of London,” vol. xxi., p. 128, and section.

[Footnote] ‡ “Trans. N.Z. Inst.,” vol. ii., p. 167.

[Footnote] § “Cat. Col. Mus.,” 1870, pp. 178, 179, and 189.

[Footnote] ∥ “Rep. of Geol. Expl.,” 1876–77, p. 41, etc.

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He ascertained that volcanic rocks underlie the Ototara limestone; while others, he thought, were associated with the Hutchinson's Quarry beds. He maintained that the Hutchinson's Quarry beds are unconformable to the Ototara limestone, and stated that the fossils prove them to be members of the same formation as the Awamoa beds (l.c., p. 58). Dr. Hector, also, in his Progress Report for the same year, says: “These higher [Hutchinson's Quarry] beds it has been impossible to separate, either stratigraphically or otherwise, from the Awamoa series which overlies them” (l.c., p. ix.). Nevertheless they are always separated in all the classifications of the Geological Survey, the latest of which will be found in the “Reports of Geological Explorations for 1883–4,” p. xiii.

In 1881, Dr. Hector says that the Ototara limestone is separated from the Hutchinson's Quarry beds by a series of volcanic rocks which belong to the upper part of the cretaceotertiary (= Waipara) period.*

In 1882, Mr. A. McKay again visited the district, and extended his observations as far south as Moëraki In his report, the blue clay and dark-green sandstones of Hampden and Otepopo (Moëraki series) are stated to underlie the Ototara limestone: thus returning to the first arrangement of Dr. Hector.

Last November I re-examined the district, and arrived at the following results:—(1.) Mr. McKay is right in saying that volcanic rocks underlie the Ototara limestone. (2.) He is probably right in his conclusion that an unconformity exists between the Hutchinson's Quarry beds and the Ototara limestone, although wrong in the reasons he adduces for it. (3.) He is wrong in his opinion that the rocks of Hampden and Otepopo are older than the Ototara limestone; and (4.), we are probably all wrong in supposing that any volcanic eruptions took place between the deposition of the Ototara limestone and the Hutchinson's Quarry beds, or during the deposition of the latter.

Before proceeding to give the evidence on which these conclusions rest, I wish to remark that my mistake as to the true position of the volcanic rocks at Oamaru arose from supposing that the pieces of limestone found in these rocks were fragments of the Ototara limestone which had been altered by heat; a defective observation, which led me to assume that the limestones which rest on volcanic rocks at Kakanui and the south-west end of Cape Wanbrow must be younger than the Ototara limestone, and consequently must belong to the Hutchinson's Quarry beds. I now find that these pieces of limestone are parts of veins in the volcanic rocks which have been formed after consolidation of

[Footnote] * “Rep. Geol. Expl.,” 1881, p. xxvii.

[Footnote] † “Rep. Geol. Expl.,” 1883–84, p. 58, etc.

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the rocks. If I had examined the Waireka Valley during my first visit to the district I should probably have found out my mistake. As the Ototara limestone is younger than the volcanic rocks, the inference naturally follows that the Hutchinson's Quarry beds, which also rest on volcanic rocks, may be unconformable to it; but the stratigraphical evidence is not conclusive, as the Ototara limestone may, perhaps, never have extended so far to the east. This question must be solved by palæontology, as I will presently point out. The specific gravities mentioned in the paper were all taken by Walker's Specific Gravity Balance, and by Jolly's Spiral Balance.

Oamaru District.

Volcanic Rocks.

I noticed four principal centres of eruption, but no doubt there are others.

1. Oamaru Volcano.—In passing along the shore from the breakwater at Oamaru towards Cape Wanbrow, we first find rocks dipping 25° N. The upper beds (Pl. XXVI., Section I., a), under the Flagstaff, are basaltic agglomerate and ash, the former with bands and pieces of fine-grained limestone. It is this limestone that in 1874 I mistook for included fragments of Ototara stone, altered into a kind of lithographic limestone. By Mr. McKay they are shown as regular beds, interstratified with the agglomerate. A careful inspection, however, has convinced me that they are all veins running between blocks of lava in the agglomerate. They are segregation veins, formed from the calcareous cement in the agglomerate and ash beds, and are of later age than the main body of the rock. The volcanic rocks in contact with these veins are not in the least altered, and the veins are usually compact and solid throughout, often with a banded structure parallel to the margin. In one instance I noticed that there was a compact layer on each side, while the central portion, varying from 6 to 12 inches in thickness, was filled in with broken shells and corals; the two inner surfaces of the limestone were quite smooth, and the organic fragments appear to have been washed in from above. Associated with these beds are tachylyte breccias, consisting of angular fragments of glossy tachylyte, rarely exceeding an inch in thickness, cemented together by crystalline calcite. Round their margins the fragments are often altered into a rich yellow-brown palagonite. The basalt of the agglomerates is compact, bluish-black in colour, finely crystalline, and with olivine more or less abundant; S.G. = 2.80. Under the microscope it is seen to consist of a microcrystalline ground-mass of felspar laths, magnetite, and pinkish brown augite grains, containing here and there crystals of slightly dichroic olivine, much decomposed round the margins

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into a dark-brown mineral. The tachylyte is formed of a pale smoky-brown glass, in which are numerous felspar laths. Here also the olivine has undergone much decomposition, a description of which I reserve for another occasion. Its specific gravity is 2.72.

Below the agglomerates comes a series of thin-bedded greenish-brown sandstones (b) containing fossils, and inter-stratified with ash beds. Below these is a coarse scoriaceous sandstone, which is underlain by grey current-bedded sandstones. Then, at the next point, comes a remarkable agglomerate (a1) formed of large basalt bombs, the interstices between which are filled up with compact fossiliferous limestone. These bombs vary from one to six, or more, feet in diameter, and some of them on the lower surface curve round those below, showing that they were soft when they fell into their places. Each bomb is encased by a coating of tachylyte about 1 inch thick, which is decomposed in places into reddish-yellow palagonite. The basalt of these bombs is rather coarser in texture than that of the agglomerate first mentioned, and I could detect no olivine with the naked eye; but under the microscope both the basalts and the tachylytes are much alike. Beyond the agglomerate, in descending order, comes (3) a series of thin-bedded sandstones and clays, dipping 20° N. Next below are (2) coarser scoriaceous sandstones, dipping 30° N., and then (1) agglomerate, (a2 in section), which gradually changes round to an easterly dip, so as to look nearly horizontal in the cliff. Then comes a fault with a hade to the north. On the south side of this fault the beds dip 25° S.E. At the top of the cliff are the thin-bedded sandstones and clays (3), underlain by the coarser scoriaceous sandstones (2), so that the downthrow of the fault is to the south, or, in other words, it is a reversed fault; the throw, however, is small. The sandstones and clays (3) extend to the next point, which is quite low; and in the following bay all the rocks are obscured by the silt deposit, which here comes down to the sea. The next point is Cape Wanbrow, formed of grey scoriaceous sandstones, dipping 10° S.E. I have given a somewhat detailed account of this section, for I am under the impression that it is at the fault that Mr. McKay supposes an unconformity to exist between his upper eocene and cretaceo-tertiary formations; but, if so, he is undoubtedly wrong. At the same time, I saw no other place where any break occurred at all.

Past Cape Wanbrow the dip changes gradually to 15° S.S.E.; then to S., then to 15° S.S.W.; and ultimately to 35° S.W. The grey scoriaceous sandstones of Cape Wanbrow occupy most of this section (Pl. XXVI., Section II.), but are overlain by a bed of pale grey tuffaceous limestone, 6 or 7 feet in thickness, containing minute fragments of coral. This is followed by

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sandstones with fossils, and then the Otatara limestone, 45 feet thick. The details of this part of the section I will defer until treating of the Hutchinson's Quarry beds.

It will be seen that the beds all round the east side of the Oamaru Peninsula form a single periclinal curve, as shown by me in 1875.* Mr. McKay's section is very different, and I am at a loss to account for it, as he gives no details.

2. Deborah Volcano.—Between the Deborah railway-station and Totara are the relics of another volcano, which has been almost entirely destroyed by denudation. The rocks are basic, but I neglected to collect specimens. So far as I could see, they always underlie the Ototara limestone, which surrounds the volcano on all sides but the south-east. Mr. McKay, however, mentions a lava flow overlying the limestone somewhere in the neighbourhood. He gives no precise locality, and I failed to find it; but as I arrived late in the day I could not make a sufficiently careful examination. In the Waireka Valley, opposite Deborah, a tachylyte tuff, probably erupted from this volcano, underlies the Ototara limestone, but I will give its position when describing the sedimentary rocks of the Ototara series. This tuff is compact, grey in colour, and with a lens shows minute black shining spots, and occasionally small pieces of vesicular tachylyte. It effervesces freely with acid, S.G.=2.47. Under the microscope it is seen to be made up of minute angular fragments of vesicular tachylyte in a calcareous cement. The tachylyte is of a pale yellow-brown colour, without any felspars, but contains a few scattered microliths. The vesicles are ovoid, not much elongated. It is much like a tachylyte tuff, presently to be described, from Lookout Bluff.

3. Enfield Volcano.—The railway at Enfield runs through an old volcano which extends as far as Elderslie (Section III.). It is formed principally by lava flows, which are compact and finely crystalline. Some are dark grey in colour, with small white pearly flecks, and cavities filled with limonite; these rocks weather reddish-grey. Others are darker, and without white flecks. S.G.= 2.64. I could see no olivine in any of them. Under the microscope these rocks are seen to have a microcrystalline ground-mass of felspar laths, brownish augite grains and ilmenite, more or less decomposed into leuxocene. There are no porphyritic crystals. In the absence of chemical analysis, I feel inclined to call these rocks augite andesites. At the road cutting close to the Waireka Presbyterian Church, there is a palagonite tuff composed of fragments of tachylyte and fragments of black magma-basalt with olivine. S.G.=2.35. The tachylyte is altered in places into a yellow-brown or brownish-green

[Footnote] * “Geology of Otago,” p. 55, fig. 7.

[Footnote] † “Rep. Geol. Expl.,” 1876–77, p. 50, section No. 3.

[Footnote] ‡ “Rep. Geol. Expl.,” 1876–77, p. 58.

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palagonite. I could obtain no direct evidence of the age of these rocks, and it is quite possible that the andesitic lava flows may belong to a later period than the palagonite tuffs. This is a point that requires more investigation than the time at my disposal would allow.

4. Kakanui Volcano.—The Kakanui River runs into the sea between two low hills formed of scoriaceous sandstone overlain by the Ototara limestone, here generally more compact than usual. (Section IV.) The sandstones of the northern hill form a periclinal curve, which extends across the river so as to include the rocks seen in the river-bed between the bridge and the sea. The south head is a separate and smaller periclinal curve, showing two foci of eruption; but I did not ascertain which of the two is the younger. I saw no lava streams.

Sedimentary Rocks.

Ototara Series.—This series consists of the Ototara limestone, known as the Oamaru building-stone, together with all the conformably underlying rocks. The Ototara stone is a rather friable and very pure limestone, capable of absorbing one-third its bulk of water. It is made up of minutely comminuted Bryozoa and Hydrocorallinæ, with Foraminifera in the interstices. The underlying beds differ in different places. In Cave Valley the rocks immediately underlying the limestone are obscured; but the railway passes through a bed of pale-yellow, non-calcareous, diatomaceous ooze, which is cut by a dyke 20 feet thick and running E.N.E., with a dip to N.N.W. (Section V.). This dyke is a compact, very dark basalt, without olivine, but with aggregations of greenish-brown augite grains with felspar laths, giving it a semi-ophitic texture. S.G. = 2.80. The dyke does not penetrate the Ototara limestone; but this cannot be taken as positive proof that it is older than the limestone, for its upper termination is not seen. I did not observe the chalk marl with flints, mentioned by Mr. McKay.

Further down the valley, at the School, volcanic rocks underlie the ooze. These volcanic rocks are seen in many places in the Waireka Valley below the Ototara limestone, and I have never seen any above it. In 1874, I observed, in a valley a little south of Cave Valley, thin-bedded, hard, dark sandstones underlying the Ototara stone. I believe that these beds come in between the limestone and the diatomaceous ooze, but I could not find them again this time. About a mile and a half south of Cave Valley the following section may be seen:—

6.

Ototara limestone.

5.

Clay.

4.

Tuffaceous clay.

3.

Palagonite tuff.

2.

Diatomaceous ooze.

1.

Volcanic rocks.

The lower part of the limestone contains small rounded frag-

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ments of volcanic rocks. The palagonite tuff I have already described when mentioning the Deborah volcano.*

A little north of Totara, on the west of the railway, the limestone rests on tuffaceous clays which dip 10° S.W., but which, towards the south, flatten to 4° S.W. In the railway cutting at Teschemaker's the limestone, here horizontal, passes down into a coarse rubble of broken shells, coral, sand, etc., and is underlain by about 8 feet of alternating beds of marl and limestone, below which is a brown volcanic sandstone, 10 or more feet thick, which appears to be derived from the degradation of volcanic ash, and not a true ash itself. It therefore appears, so far as my observations go, that volcanic action took place before and during the deposition of the marls and clays underlying the limestone, but there are no volcanic ashes in the limestone itself. The volcanic action was chiefly submarine, but the water was shallow.

The geographical distribution of the Ototara limestone has been described by Mr. McKay. The dips I observed were as follows:—At Cave Valley, 5° E.N.E.; near Totara railway-station, on west side of the road, 5° N.W.; on the east side, between the road and the railway, 4° to 10° S.W.; at north side of Deborah, 5° N.N.E.; on south side of Oamaru Peninsula, 35° S.W. Now, Oamaru Peninsula, Deborah, and Enfield are old volcanoes, consequently the Ototara series dips away from the nearest volcanic centre. This shows, in my opinion, that the Ototara limestone is the remains of several old coral reefs built up round small volcanic islands near the coast, and that it usually retains its original plane of deposition. Limestones are known to be forming at the present day, at angles as great as 33° and 35°, on the coral-reefs of Florida and the Solomon Islands.

Hutchinson's Quarry Beds.—This quarry is situated in the town of Oamaru, on the east side of Oamaru Creek, close to the path leading to the reservoir. It is now abandoned, but was formerly used for lime for burning. The following is the section displayed:—

Feet.
8. Dark-green sandstone 6 fossils
7. Calcareous sandstone 8–10 fossils
6. Conglomerate of volcanic rocks and compact limestone 10
5. Volcanic clay 1 ½–2
4. Compact limestone 0 ¾
3. Volcanic clay 0 ¾
2. Rubbly limestone 3
1. Volcanic clay, with calcareous veins 13

[Footnote] * To find this interesting outcrop, take the road from the Deborah railway-station to the quarry, and, leaving the quarry on the right, strike across the fields to the crest of the ridge. Then, looking down into the Waireka Valley, the section will be seen on the left hand.

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Owing to a slip, the relation of Nos. 7 and 8 to the rest is not clear in the quarry, but higher up the creek No. 7 is seen resting on No. 6. All the fragments in the conglomerate are well rolled, and the volcanic clays appear to be detrital only. The beds are surrounded to the west and south by the volcanic rocks upon which they lie; to the east they are covered by silt; while to the north they extend for some distance along the east side of Oamaru Creek. I could find, however, in this part of the district, no junction with either the Ototara limestone or with the Awamoa series.

At Deborah, in a small railway-cutting, a little north of the station, the following rocks are seen, dipping 15–20° N.E.:—

3.

Calcareous greensand.

2.

Conglomerate of rolled volcanic rocks and limestone.

1.

Ototara limestone.

The junction between Nos. 1 and 2 appears to be unconformable, but the cutting is too small to feel confident on this point.

At the south end of Oamaru Peninsula, we get the following section, all the beds dipping 35° S.W.:—

Feet.
12. Blue sandy clay with calcareous concretionary layers.
11. Green sandstone, with calcareous concretions near the top 25
10. Hard compact limestone 4–5
9. Limestone, with rolled volcanic fragments 12
8. Ototara limestone 33
7. Clay, with three bands of Bryozoon limestone 7
6. Ototara limestone 5
5. Volcanic conglomerate, with calcareous matrix 3
4. Blue ashy sandstones, with shells 150
3. Thin bedded sandstones 12
2. Grey tuffaceous limestone 6–7
1. Scoriaceous sandstones 200+

No. 12 belongs to the Awamoa series; Nos. 9, 10, and 11 to the Hutchinson's Quarry beds; and all below to the Ototara series; but I could make out no unconformity between any of them. Here, as elsewhere, I came to the conclusion that volcanic action had ceased before the deposition of the Ototara limestone, and that it was not renewed during the deposition of the Hutchinson's Quarry beds.

At the south-west end of the southern hill, at Kakanui mouth, where the plains begin which stretch to the Otepopo River, the Ototara limestone, dipping 20° S.W., is overlain unconformably by dark-blue sandy clay, dipping very slightly

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to S.W. at the point of junction, and then getting horizontal as it passes south along Allday Bay. In this clay I obtained Dentalium mantelli, Ostrea edulis, Waldheimia patagonica, and Cellepora nummularia; but many more species could be obtained with plenty of time. I believe this clay to be the equivalent of the Hutchinson's Quarry beds, but more palæntological evidence is required. The unconformity between it and the underlying limestone is plainly to be seen in the coast section, not only in the difference of dip, but also in the denuded surface of the limestone (Section IV.).

The Hon. W. Mantell makes the following remarks on this locality: “A mile south of Kakanui, strata of tertiary blue clays first appear; they contain numerous shells of species that in-habit the neighbouring sea, corals, a few traces of fishes, and small portions of wood. In some localities the clay is capped by a thin layer of sandstone.”* If the Hutchinson's Quarry beds are the same as this clay, then they must no doubt be placed, for reasons that will presently be given, in the Pareora System with the Awamoa series. I have already mentioned that Mr. McKay formerly held the opinion that the fossils were the same in both, although the Geological Survey has never grouped them together.

Pareora System.—I have already mentioned the Awamoa beds on the south side of Oamaru Peninsula, so well known from the collections made by Mr. C. Traill in 1868. The same beds occur on the eastern side of the hills north of Oamaru, as far as the Waitaki Valley. The only other place in the district where I saw rocks which I should refer to the Pareora System was in the Waireka Valley. Here, in going from Elderslie to Windsor, we see blue clay, which, further north, passes upwards into white quartz sands and gravels, covered from Corriedale to Ngapara by a hard conglomerate, formed by well-rounded white quartz pebbles in a ferruginous cement (Section III.). These form conspicuous cliffs, which cap the hills on both sides of the railway. I did not find any fossils in these beds, and cannot, therefore, pronounce positively as to their age, but it was from somewhere in this neighbourhood that Mr. C. Traill made a collection of Pareora fossils some years ago. I cannot, indeed, conceive these beds to be older than the Ototara limestone, as supposed by Mr. McKay; and in November, 1873, I found the quartz pebble beds resting on the limestone near Mr. R. Gillies' farm, in the Awamoko District. The lignite, which lies also above the limestone, is here generally covered by the ferruginous conglomerate. These beds appear to me to be like the Pareora gravels and conglomerates of Waihao and other places, and to occupy a valley of erosion in the Oamaru System.

[Footnote] * “Quar. Jour. Geol. Soc. of London,” vol. vi., p. 324.

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In his earlier report, Mr. McKay says: “The outlier of these rocks [Pareora] between the Kakanui River and the Upper Waireka shows them to be quite unconformable to the Ototara limestone and the tufas and greensands underlying the limestone, as the limestone is absent and the conglomerates and blue clay seem there to lie on the tufas and basaltic rocks which are the northern continuation of the Mount Charles rocks at Otepopo. This conclusion is quite irresistible, if we consider the upper part of the valley of the Waireka as due to denudation, and not to a fault, which latter it could not well be.”* It will be seen that my observations confirm this (except the relation to the rocks of Mount Charles); but in his last report Mr. McKay abandons his former views without any remark except the statement that these beds are overlain by the Maerewhenua limestone, for which he adduces no evidence, and gives no section nor list of fossils. Mr. McKay, however, collected fossils in the Upper Waireka Valley, as well as beyond the first tunnel on the Windsor-Livingstone railway, which will, I hope, settle the question when they have been accurately named.

Silt Formation.—In my report on the Geology of Otago in 1875, I gave a section of the silt deposit, or loëss as it has been called, on the north side of Oamaru Peninsula, and stated that it rested upon gravels with marine shells. Quite lately Dr. Hector has called this in question. He says: “As far as I have observed, the presence of such shells under silt can always be accounted for by landslips of the slope deposit.” I therefore paid particular attention to this point, and can state confidently that on the north side of Oamaru Peninsula gravels with marine shells undoubtedly underlie the silt conformably. The cliffs have here been cut back for some distance to form the railway to the port; all traces of raised beaches, if they formerly existed, have been removed, and a true section has been exposed; as is proved by the intercalations of gravel and silt. But more than this: at the place where the railway sidings commence at the port, the cutting has exposed a large cave in the volcanic rocks which has been filled up to the roof with silt. On the floor of this cave are the gravel beds with marine shells, and these are covered by well-stratified sandy beds, passing up gradually into the silt, which is continuous with that of the rest of the cliff, as is clearly seen in the cutting. In this case a landslip is impossible, for the beds are covered by the roof of the cave; and if the fossiliferous beds pass under the silt here they must also do so in other parts of the cutting. On the south side of the peninsula, slips have, no doubt, occurred in places; but even

[Footnote] * “Rep. Geol. Expl.,” 1876–77, p. 57.

[Footnote] † “Rep. Geol. Expl.,” 1883–84, p. 59.

[Footnote] ‡ “Rep. Geol. Expl.,” 1883–84, Progress Report, p. xxv.

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here it is quite evident that the gravels have slipped with the silt, and that both retain their relative positions. North of Oamaru many road sections show the silt to be distinctly interstratified with gravel beds, but I observed no fossils in them.

Hampden District.

Sedimentary Rocks.—Onekakara Bay lies between the Peninsula of Moëraki and Lookout Bluff, just south of the mouth of the Otepopo River. Hampden is a little to the south of the centre of the bay (Section VI.). The sedimentary rocks consist of blue clay (Onekakara clay), overlain by a soft dark volcanic sandstone, or rock-sand, which weathers greenish; the whole being covered by beds of gravel and silt. The sandstone is found chiefly north of Hampden, but it also occurs at Moëraki. It is in the blue clay, south of Hampden, that the Moëraki septaria are found.

The sandstone consists largely of well-rounded volcanic débris, and is black on first breaking, but soon turns greenish. A similar soft sandstone is largely developed in the banks of the Otepopo River, near the railway; it differs in being almost entirely a volcanic sand, and in weathering to a distinct green colour. The sandstone here is also underlain by blue sandy clay, with dark soft sandstone again below it. It is this latter sandstone which occurs at the Herbert tunnel. Small beds of lignite are associated with it, which were explored by Mr. Fenwick in 1875.

As I have already mentioned, the age of these beds is a matter of difference of opinion. In 1884, Mr. McKay divided them into three divisions, all of which he considered to belong to the cretaceo-tertiary or Waipara System. The stratigraphical evidence he produces in favour of this view is the mistaken idea that they are overlain by the tuffs below the Ototara limestone in the Waireka Valley; this relation depending entirely on the supposed equivalence of the volcanic rocks of Mount Charles and of Kakanui. Of palæontological evidence, Mr. McKay adduces none, for he gives no list of fossils; but to get rid of the evidence in favour of their miocene age, he makes two most extraordinary statements:—

  • (1.) Previous collectors have “imperfectly collected at points where slips have mixed them [fossils] with the recent shells of the coast-line.”

  • (2.) Previous palæontologists have examined a mixture of cretaceo-tertiary and recent shells, “hence possibly one reason why these beds have been by some previous observers referred to the miocene period.”*

[Footnote] * “Rep. Geol. Expl.,” 1883–84, p. 62.

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With reference to the first statement, it is not easy to believe that either the Hon. W. Mantell or Mr. C. Traill mixed together fossil and recent shells. Mr. Traill's collection is still in existence, partly in the Wellington Museum and partly in that at Dunedin; and, as most of the fossils are still in their original matrix, it is easy to disprove Mr. McKay's statement in this case. Mr. Mantell's collection is not in the Colony, but his list does not contain any of the commoner shells found on the coast. South of Hampden there is a raised beach with recent shells (Section VI.,f), formed into a quartzose sandstone, which, at first sight, might be supposed to pass below the clay. The commonest fossils in it are Barnea similis, Mactra discors, Paphia spissa, Venus mesodesma, Venerupis reflexa, and Ostrea edulis; but as none of these genera, except the last, occur in Mr. Mantell's list, he could not have made any part of his collection here. The idea that a palæontologist, having before him a collection of cretaceous and recent shells, should, as it were, strike a mean and consider the whole to be miocene—although, of course, not a single characteristic miocene shell would be among them—needs no refutation.

To test the accuracy of these statements, I collected myself for an hour or two, in the blue clay north of Hampden, at the place marked “Fossils” in Section VI., with the following result:—

1.

Ancillaria australis

*2.

Voluta corrugata.

*3.

Pleurotoma fusiformis.

4.

Turritella ambulacrum.

*5.

Turritella ornata.

6.

Trochus (?impression only).

7.

Dentalium mantelli.

8.

Venus stutchburyi.

*9.

Solenella funiculata.

*10.

Limopsis insolita.

11.

Cucullœa, sp. (fragments).

12.

Pecten hutchinsoni (right valve).

13.

Pecten hochstetteri (? fragment).

14.

Ostrea edulis.

*15.

Trochocyathus mantelli.

16.

Notocyathus pedicellatus.

Of these 16 species, the three in Roman are still living, and the six marked with an asterisk are characteristic Pareora (i.e. miocene) species. This is, I think, quite sufficient to show that Mr. McKay is in error, but I will give a list of all the fossils reported from this locality:—

1.

Aturia ziczac, Sowb.

2.

Fusus australis, Quoy. and Gaim.

3.

Siphonalia nodosa, Martyn.

4.

Siphonalia nodosa, var. conoidea, Hutton.

5.

Cominella, sp. ind.

6.

Nassa tatei, Tenison-Woods.

7.

Ancillaria australis, Sowb.

8.

Voluta pacifica, Solander.

9.

Voluta corrugata, Hutton.

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10.

Pleurotoma fusiformis, Hutton.

11.

Pleurotoma buchanani, Hutton.

12.

Triton spengleri, Lamarck.

13.

Natica neozelanica, Q. and G.

14.

Natica suturalis, Hutton.

15.

Cerithium cancellatum, Hutton.

16.

Struthiolaria papulosa, Martyn.

17.

Trochita neozelanica, Lesson.

18.

Crepidula monoxyla, Lesson.

19.

Turritella rosea, Q. and G.

20.

Turritella tricincta, Hutton.

21.

Turritella ambulacrum, Sowb.

22.

Turritella ornata, Hutton.

23.

Trochus(?), sp. ind.

24.

Dentalium mantelli, Zittel.

25.

Venus stutchburyi, Gray.

26.

Cytherea multistriata, Sowb.

27.

Trigonia pectinata(?), Lamarck.

28.

Solenella funiculata, Hutton.

29.

Pectunculus laticostatus, Q. and G.

30.

Limopsis insolita, Sowb.

31.

Cucullæa, sp. ind.

32.

Mytilus magellanicus, Lamarck.

33.

Pecten hochstetteri (?), Zittel.

34.

Pecten hutchinsoni, Hutton.

35.

Ostrea edulis, Linneus.

36.

Entalophora zealandica, Mantell.

37.

Notocyathus pedicellatus, Tenison-Woods.

38.

Trochocyathus mantelli, M. Edw. and H.

39.

Trochocyathus hexagonalis, Mantell.

Some of the recent shells of this list may have been wrongly named, but it must be noticed that of the 32 named species of Mollusca (including the variety), all but Struthiolaria papu-losa, Cerithium cancellatum and Trigonia pectinata have been found in Pareora rocks in other places in New Zealand; and, of the exceptions, the first two occur in the Wanganui System, while the third (doubtfully identified) has not been found in any other part of New Zealand. Of the 29 Pareora species, 14 are not known older than the Pareora, 5 are not known younger than the Pareora, 7 are found in the Pareora only, and 3 go through all our tertiary rocks. Aturia ziczac occurs in New Zealand at Waihao Forks, with numerous Pareora fossils. The genera Cominella and Ancillaria are not known from mesozoic rocks in any part of the world. Entalo-phora zealandica is found at Wanganui, and in miocene rocks in South Australia. Trochocyathus mantelli occurs in the Pareora beds at Mount Horrible, near Timaru.

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The evidence is, I think, conclusive that the Onekakara clay belongs to the Pareora System. And this being so, it follows, almost certainly, that the clay overlying the limestone a mile south of Kakanui, which has been followed by Mr. Mantell through Allday Bay to the Otepopo River, also belongs to the Pareora System; and if it is the equivalent of the Hutchinson's Quarry beds, as I suppose, they too must be put into the Pareora. The only evidence wanting is the comparison of the fossils from Hutchinson's Quarry with those from the clay near Kakanui, and this I am not able to do as my lists are not sufficiently complete.

Volcanic Rocks.—The north side of Moëraki Peninsula is formed by dolerites (S.G. = 2.88), which are seen on the shore to overlie the Onekakara clay, here dipping 0° to 60° S.S.E. In one place I noticed, in 1873, that the blue clay had been altered by contact of a lava flow, and turned white for a distance of 2 to 4 feet. These volcanic rocks are therefore much younger than those described from the Oamaru District. Mount Charles, between Herbert and the Otepopo River, is also formed of dolerites, which appear to overlie the greensands and blue clay; at the same time the greensands are formed almost entirely of volcanic detritus derived from still older rocks. These dolerites closely resemble those from Moëraki, but are sometimes coarser in grain, and a less specific gravity (2.73), owing probably to their being more altered. They are compact, and dark greenish-grey in colour, or paler, owing to scattered greyish-white flecks which sometimes become very abundant. Under the microscope they are seen to be holocrystalline, without any older generation. The felspars are in lath-shaped crystals, usually polysynthetic. Sections, more or less parallel to the brachydiagonal, gave extinction angles up to 15° with the twinning plane; while long narrow sections, more or less at right angles to the brachypinacoid, gave extinction angles up to 45°. From this I judge the felspar to be labradorite. Augite of a pale olive-brown, sometimes with black margins, occurs in imperfect crystals; and in a slide from Mount Charles I found a well-defined crystal of rhombic pyroxene, giving straight extinctions. This pyroxene is slightly dichroic, the vibrations parallel to the macrodiagonal being pinkish-green, and those parallel to the brachydiagonal olive-green. This pyroxene is not striated, and, therefore, I suppose it to be enstatite. Ilmenite is abundant, generally in thin plates from Moëraki, but more irregular from Mount Charles; it is much altered into leucoxene, which makes the white flecks. No olivine was seen in any of these rocks.

Lookout Bluff (the “White Bluff” of Mr. Mantell's paper already referred to) is an old and much-denuded volcano, composed chiefly of agglomerate and ash beds. To the north, scoriaceous sandstones, dipping to W. at various angles up to

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45°, reach the Otepopo River, and their relation to the blue clay in Allday Bay cannot be ascertained; but to the south a series of dark-green soft sandstones, weathering reddish-brown, dipping 25° W., and underlain by blue clay, are apparently interstratified with tachylyte tuffs. I could find no fossils in these rocks; and, unfortunately, they are separated from the Onekakara clay by a mass of silt and gravel, so that here also their relations are not quite certain, although I saw no reason to doubt their identity with the Onekakara clay. One tachylyte which I collected is a compact, dull, earthy, black rock, and looks like a dark clay; it breaks up irregularly into small fragments, generally with curved surfaces (S.G.= 2.14) It is minutely cracked in all directions, is not vesicular, and of a clear olive-brown, in places paler with globulites, sometimes scattered, sometimes collected into irregular but sharply defined patches, generally angular, but often in lines. Other parts are darker, with abundant globulites. There are no microliths. Another specimen was dark blue-black, with a crystalline texture, and rounded black globules among the crystals (S.G. = 2.38). Under the microscope this is seen to be a tuff, made up of fragments of a brownish-yellow vesicular tachylyte in a crystalline calcareous cement. The vesicles are elongated in the same direction, but there is no other fluxion structure. These tachylyte rocks resemble those from Waireka Valley and White-water Creek in the Trelissick Basin, all of which belong to the Oamaru System. Whether they are or are not of the same age must remain for the present an open question. Their peculiar structure is probably due to lava streams, which have run rapidly into water and have been shattered into minute fragments.

Conclusion.

In a paper read before the Geological Society of London, in June, 1885,* I have taken it for granted that the Hutchinson's Quarry beds formed part of the upper eocene, or Oamaru System; and that the volcanic outbursts at Oamaru were contemporaneous with them. This was my former view, but I know now that I was wrong in one, and perhaps in both, of these points. The alterations, however, do not affect in any way the general drift of that paper, which is to show that the fossils of the upper part of the cretaceo-tertiary and of the upper eocene formations of the Geological Survey are identical, and that there is no stratigraphical break between them—i.e., between the Curiosity Shop beds and the Otakaika limestone as representing the upper eocene, and the Ototara and Maerewhenua limestones as representing the cretaceo-tertiary. My repudia-

[Footnote] * “Quar. Jour. Geol. Soc. of Lond.,” vol. xli, p. 547.

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tion of Mr. McKay's arguments in favour of unconformity between the Hutchinson's Quarry beds and the Ototara limestone remains intact, although I now, for other reasons, think his conclusion probable. The only alteration necessary to make in my paper is to erase the words I have italicised in the following sentence:—” Cape Oamaru is formed by an old volcano, which has broken through the Ototara limestone, and was active when the marine beds of Hutchinson's Quarry were being deposited.” (l.c., p. 561.)

Art. LV.—Note on the Geology of the Valley of the Waihao in South Canterbury.

[Read before the Philosophical Institute of Canterbury, 6th May, 1886.]

In 1875, Dr. von Haast sent to the Otago Museum a collection of fossils from Whiterock River; Mount Harris; Point Hill, Waitaki; and Waihao Forks, with the request that I would examine them. The results of my examination went to show that the whole collection belonged to the Pareora System.* Dr. von Haast agreed with me as to the age of the fossils from the first three localities, but had doubts about those from the greensands at Waihao. He says: “These greensands are overlaid by calcareous greensands with all the characteristic fossils of the Oamaru formation, on the edges of which the Pareora formation reposes unconformably; consequently a careful study of the more extended collections from these beds is needed to settle this point to my satisfaction.” In October, 1880, Mr. A. McKay examined the district for the Geological Survey of New Zealand. In his report he classes these beds, which he calls “marly greensands,” with the cretaceo-tertiary series of the Survey, and in his map he marks them as lower cretaceo-tertiary. He thus agrees with Dr. von Haast that they underlie the Waihao limestone, but he makes no reference to the disagreement between the palæontological and the stratigraphical evidence, and appears to see no difficulty at all in the structure of the district. Last year I examined the collection of fossils in the Canterbury Museum from Waihao, and in December I paid a visit to the district to try to clear up the difficulty.

[Footnote] * “Trans. N.Z. Inst., vol. ix., p. 594.

[Footnote] † “Geology of Canterbury and Westland, 1879,” p. 315.

[Footnote] ‡ “Reports of Geological Explorations for 1881,” p. 71.

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The right bank of the Waihao River, from a little above the Forks down to the bridge by which the road from Arno to Waikakahi crosses the river—a distance of about three miles—is formed by rocks of the Oamaru System. A northerly extension of these rocks, rather more than a mile in breadth, crosses the river about half a mile below the Forks; so that, for this distance, the Oamaru System* forms both banks of the river. On these points all are in agreement. The rocks belonging to the Oamaru System here are—

3.

Pale-yellow arenaceous limestone, about 50 feet thick, known as the Waihao limestone.

2.

Calcareous sandstone, with green grains, 150 feet.

1.

Dark-grey marl, getting more sandy at the top, with ferruginous bands or veins; thickness, 50 feet +; contains Pecten zittelli.

No rock is seen to underlie this marl anywhere between the forks of the Waihao and its mouth.

On the left bank of the river, both above and below this northerly extension of the Oamaru System, we find thick (200 feet +) beds of soft dark-green or grey argillaceous sandstone, sometimes with calcareous concretions, and containing numerous fossils (see fig.) It was from these beds that Dr. von Haast collected the fossils sent me in 1875. They are also the “marly-greensands” of Mr. McKay's report. The point to be settled is: Do these greensands underlie the marl of the Oamaru System? or do they lie unconformably against the eroded edges of that system?

The palæontological evidence is decidedly in favour of the second of these suppositions, as the following list of fossils from the Waihao Forks will show:—

1.

Teeth of crocodile (?).

2.

Aturia ziczac, Sowb.

*3.

Siphonalia nodosa, Martyn.

*4.

Ancillaria australis, Sowb.

5.

Ancillaria hebera, Hutton.

*6.

Voluta corrugata, Hutton.

*7.

Pleurotoma fusiformis, Hutton.

*8.

Pleurotoma buchanani, Hutton.

*9.

Pleurotoma awamoaensis, Hutton.

*10.

Clathurella hamiltoni, Hutton.

11.

Natica gibbosa, Hutton.

12.

Natica hamiltoni, Tate.

*13.

Natica suturalis, Hutton.

14.

Dentalium mantelli, Zittel.

[Footnote] * For a list of fossils found in these rocks, and a discussion as to their age, see “Quar. Jour. Geol. Soc. of London,” vol. xli., p. 559.

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15.

Teredo heaphyi, Zittel.

*16.

Leda fastidiosa, Adams.

17.

Pecten hochstetteri, Zittel.

18.

Flabellum circulare, Tenison-Woods.

Of these 17 species, all have been found in rocks of Pareora age except Leda fastidiosa, which is a recent species, only known fossil at Wanganui, and Flabellum circulare, which, however, occurs in both the Oamaru and Wanganui Systems. The nine species marked with an asterisk are not known anywhere in rocks older than the Pareora. Ancillaria hebera, Natica gibbosa, and Dentalium mantelli, are common Pareora species, but rarely found in the Oamaru System. Aturia ziczac occurs in Europe and in North America in the upper eocene and lower miocene only; in Australia it is found, according to Professor McCoy, in the oligocene, the miocene, and the pliocene. Consequently the palæontological evidence is decidedly in favour of these greensands belonging to the Pareora System.

The stratigraphical evidence is not so satisfactory, for no clear sections exist. It is possible—from a stratigraphical point of view—that these greensands might pass under the marl of the Oamaru System, although they occur at a higher level than the marl; because there is some evidence that the northerly extension of the Oamaru System lies in a flat syncline. But in no case are they seen either to pass below the marl or to lie upon it; consequently the palæontological evidence must be taken as proving the superior position of the greensands.

Mr. McKay, in making out his case, says (l.c., p. 72) that at Elephant Hill these greensands are succeeded directly by the Pareora System, which would be quite in accordance with the view that they themselves belong to that system; but Mr. McKay, in his section, shows an unconformity between them. This unconformity, however, does not appear to have been directly observed by Mr. McKay; and his section is evidently a hypothetical illustration of his views, and not a simple record of observed fact. This is at once seen by looking at his section, which is an impossible one. Mr. McKay says: “In the section above sketched, the marly greensands terminate at a peculiar fucoidal band, which in the Waihao River is seen to occupy the middle part of these greensands; the succeeding beds are the characteristic marine part of the Pareora formation, and unconformityis therefore manifest at this point. Not half a mile distant from the point of unconformity represented above, the lower part of the section is complete as high in the series as the Waihao limestone, which is overlaid unconformably by the Pareora beds. On the south side of the Maerewhenua River the marly greensands and coal rocks underlie in direct sequence the Maerewhenua limestone, and at no point do they come in contact with marine tertiary rocks” (l.c., p. 73).

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I have elsewhere examined Mr. McKay's statements as to the age of the greensands at Maerewhenua and Wharekauri,* and I will here only remark that he gives no evidence to show that they are the equivalents of the greensands at Waihao. Indeed, unless his Nautilus danicus is Aturia ziczac, he does not mention a single species common to both. For the present, therefore, the position of the Maerewhenua greensands cannot be taken as furnishing any evidence of the age of the greensands at Waihao.

With reference to the first part of the paragraph I have quoted, not much weight can be attached to the position of the “peculiar fucoidal band,” which is not mentioned elsewhere by Mr. McKay, and if unconformably overlain, could not always form the top of the greensands here. The evidence for the unconformity really rests on the absence of the Waihao limestone at this place, although found half a mile off. This, however, proves nothing; because it is the relative position of the limestone and the greensands which is the doubtful point; and to introduce an unconformity into the section because the limestone is absent, is to assume as true the very point which it is wished to prove.

Another exposure of the Oamaru System occurs on the right bank of the Waihao River just before it enters the plains. The rocks here are much obscured, and I failed to make out the section given by Mr. McKay. To me it appeared more like an inlier, surrounded unconformably by the Pareora System. According to Dr. von Haast, the Pareora System fills up valleys denuded out of the Oamaru System north of Elephant Hill, and there is no difficulty at all in supposing that these Pareora rocks cross both the south and north branches of the Waihao, and wrap round the rocks of the Oamaru System as far as the Waimate Hills. The annexed woodcut illustrates my view of the relation of the rocks, but it is of course to some extent hypothetical, as no positive stratigraphical evidence is available.

[Footnote] * “Quar. Jour. Geol. Soc. of London,” vol. xli., pp. 558 and 562.

[Footnote] † “Geology of Canterbury and Westland,” Sheet of Sections No. 5, Section No. 4.

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Art. LVI.—The Waihao Greensands, and their Relation to the Ototara Limestone.

[Read before the Wellington Philosophical Society, 20th October, 1886.]

Differences of opinion possibly are never wanting in connection with material advances in such sciences as are dependent on accurate observation and sound judgment, and in this respect geology in New Zealand has nothing to complain of; for whether as regards Tertiary, Secondary, or Primary formations, differences of opinion exist, and have led to the necessity of supporting particular views at greater length than would otherwise have been needful.

In the particular case I have to refer to on this occasion, the dispute concerns localities and beds rendered classical by the observations of the Hon. Mr. Mantell more than 40 years ago, differences of opinion even now existing with respect to the stratigraphical position of the Onekakara and Hampden beds, in the Moëraki District of Otago. These beds are placed by the Geological Survey as belonging to the Cretaceo-tertiary series; by Sir Julius von Haast as being of older Tertiary date; and by Professor Hutton they are referred to the Upper Miocene period. The Survey and v. Haast support their contentions with facts both stratigraphical and palæontological; Hutton's contentions are based almost wholly on palæontological grounds.

South of the Kakanui River the beds in dispute are not overlaid by the Ototara limestones of Oamaru, these being denuded from the Moëraki District; but in the district north of the Kakanui, and in Southern Canterbury, the Survey and v. Haast agree in placing the equivalent beds under the Ototara limestone; and in the Waihao Valley it has been held that this position of the greensands can be demonstrated. Hutton admits that the Waihao limestone is the equivalent of the Ototara stone, or at all events belongs to the “Oamaru formation,” and also admits that the Waihao greensands are the equivalents of the Onekakara beds, but holds that the greensands are younger than the limestones, and, with the Onekakara beds, belong to the Pareora formation. North of Timaru the same greensands occur in the valley of the Kakahu River, and here also, by v. Haast and the officers of the Geological Survey, are said to underlie a representative of the Ototara limestone. Hutton believes that the greensand beds only appear to pass under the limestones in the Kakahu, and considers them as showing this apparent relationship in consequence of a fault, supposed to be present, but which has not yet been observed.

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In 1865, the Director of the Survey placed the Hampden (Onekakara) beds below the calcareous rock of Oamaru, and the Caversham sandstone near Dunedin, referring both to the Eocene period; and in 1877 included them in the Cretaceotertiary series. In 1873, Hutton referred both the Hampden and the Kakahu beds to Upper Miocene; and in 1875, after having examined the stratigraphy, was confirmed in his opinions respecting the Miocene age of the Hampden beds. During 1867–68, v. Haast made collections from the Waihao green-sands, etc., which he forwarded to Otago Museum in 1875. These were examined by Hutton, who in the following year published a description of the new species the collection contained, and at the same time referred the Waihao greensands to the Pareora formation. In 1879, v. Haast took exception to the reference of the Waihao greensands to the Pareora formation, and, detailing the sequence, showed clearly that they underlaid the limestones belonging to the Oamaru formation. In 1880, I examined the geology of the Waihao Valley, and agreed with v. Haast that the greensands of the Waihao Forks underlaid the limestones in the near vicinity, and differed from him only in this, that I ascribed his Oamaru formation to the Cretaceo-tertiary period. In 1884, Lindop arrived at the same conclusion, as far as concerned the relative position of the greensands and the limestones.

In 1873, Professor Hutton expressed the opinion that our young secondary and tertiary rocks are in many instances deposits accumulated in the narrow valleys of a submerged land;* and in 1875 he argues that, after the close of the Eocene period, these valleys were in some instances re-excavated and others formed, within areas covered by cretaceous and upper eocene deposits; and, in Upper Miocene times, were again filled with marine deposits. In this way he finds the stratigraphy of some districts of the east coast of the South Island very perplexing, and would have us believe that the so-called miocene beds appearing to pass under the upper eocene deposits in reality flanked them on the inland side, or filled valleys excavated in them. This theory, though it obviated the necessity of grappling with a serious palæontological difficulty, led but to another, as it implied the existence in cretaceous times not merely of the principal outlines of the physical configuration of the country, but of many of the minuter details, and at the same time the existence of a profusion of fords and islands along the coasts of eastern Otago and South Canterbury during miocene times. Most other geologists holding that the phenomena thus to be explained were capable

[Footnote] * “Geological Reports,” 1873–74. p. 37.

[Footnote] † “Geology of Otago,” 1875, p.—.

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of being accounted for in another way, this theory has not been generally accepted, and for a time seems to have been lost sight of even by its author.

This theory was intended to explain how the Onekakara and Waihao greensands might appear as though they underlaid the Ototara limestone and yet be younger than the limestones. In 1885 Hutton appears to have altered his opinion respecting the position of the Waihao greensands, as he includes them with other beds in the Oamaru System, and as in position underlying the Ototara limestone. However, having in the meantime examined the Lower Waitaki Valley, the neighbourhood of Oamaru, Kakanui, and Hampden, and the Waihao Valley, where the greensands and limestones appear, he revives the fiord-island theory as the only one consistent with the palæontological evidence he brings forward.

Selecting the Waihao Valley, as affording most convincing proofs of the correctness of his theory, on the 6th of May, 1886, he read before the Canterbury Philosophical Institute a paper, in which he discusses the relative age of the Waihao Forks green-sands and the limestones on the south side, opposite the Forks, and further down the river. In thus selecting the lower basin of the Waihao as the battle-ground within which the issues of the dispute are to be decided, he promised himself one or two advantages not afforded by other localities that might have been chosen. Here the stratigraphy was less decisively in favour of the opposing view than at the Kakahu, and the palæontological evidence as much in his favour as at Hampden.

In the Waitaki Valley there was no disputing the position of the greensands in relation to the limestone members of the Oamaru formation; while at Mount Royal, and near Palmerston, the greensands had afforded him no palæontological evidences. Hampden and Onekakara, from the absence of the limestone there, failed to yield that measure of stratigraphical proof which was requisite to set off the superior claims of palæontology; while at the Waihao, if v. Haast did not support his views, at least he did not favour those of the Geological Survey.

After examination, he decided that the stratigraphical evidence is obscure, but more in favour of his own theory than that of v. Haast, or of the Geological Survey. He discredits the evidence of sections he does not understand, and characterises as impossible others that he did not see.* He totally ignores v. Haast's description of the sequence, and is equally silent as to the nature of the beds upon which the greensands rest. He proves in nothing the correspondence of the greensands with

[Footnote] * The sections on the Waihao, at the south end of the Waimate Hills, and that at Elephant Hill, are here alluded to. With reference to the last, there is nothing in Professor Hutton's “Note on the Geology of the Waihao Valley” leading to the belief that the locality was visited by him.

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any of the beds forming Mount Harris, and seems to think that most characteristic greensands may, through a vertical thickness of 200 feet, alter to beds of a totally diverse character in the horizontal distance of a few feet; and, amazed at the difficulties that beset his own explanation of the sequence, marvels that I could not discover the like from my point of view. Yet, regardless of what may follow, he decides that there is no proof of the greensands underlying the limestone; and, dismissing this part of his subject, is satisfied that the palæontological evidence is less unsatisfactory. This would indeed seem to be the case.

According to Hutton's lists of fossils, the palæontological evidence is to all appearances decisive. Sixteen species of Mollusca are known; all of them said to have come from the Waihao greensands: the collections of 1867–68, named by him in 1876; and collections (of latter date?) now in the Canterbury Museum, 8 more, making 24 in all. Twenty-four, it would appear, then, are known to him, and in the Canterbury Museum; yet only 16 species are now cited by him—what of the remaining 8 species? They were sent by v. Haast to the Otago Museum and named by Prof. Hutton in 1876. They are cited as fossils of the “Waihao” in the “Geology of Canterbury and Westland,” and now they are not! What has become of them? Lost? No; for their record remains. But we have 16 left, the 16 that now constitute the fauna of the Waihao greensands. What of them? They have all been found in the Pareora formation: 9 of them have never been collected from beds of greater age, and 5 of them are actually living forms. Of the 16 species from the Waihao greensands, 9, or nearly 57 per cent, are unknown as coming from the Oamaru formation, and 60 per cent, are in like case, taking the Pareora formation as a whole; therefore the Waihao greensands are typical Pareora beds; and there is no need to inquire how their fossils stand related to those found in the neighbouring Mount Harris beds. The stratigraphy has been wrongly read hitherto, is difficult of decipherment, and at best obscure.

If we admit all these premises, there can be no doubt, identifying myself with the stratigraphists, that ours is a desperate case; at least, it looks so on paper—hardly so bad along the banks of the Waihao.

Last June I paid a short visit to the Waihao, and first examined the section at the Waihao Forks, south to the limestone scarp. I could not avoid the conclusion that the green-sands dipped south and passed under the limestone. I followed up the first creek below the junction, and in the west branch of that found it had cut through the limestone and exposed the greensands. I tried the middle branch with the like success, and that to the east with the same result. I examined the south bank of the river more to the east, and, opposite the

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western end of the limestone, on its north bank, had further proof of the inferior position of the greensands.

Here a small stream, coming from the northern slopes of Mount Harris, joins the Waihao. Part of its course is through a limestone gorge; nearer its junction with the river the limestone walls diverge, but again approach towards the infall of the creek. The basement beds of the limestone are 20 to 30 feet above the creek at its junction with the river on the east side, and higher on the west side. On the west side the limestone forms a high bluff overlooking the river, which sets as a deep pool at its foot. The lowest beds seen are dark, almost black, with greensand grains. The creeklet ripples over these into the pool. On the right hand (down the river) they form a flat ledge above ordinary flood-mark. Fossils were collected here, the same species as at Waikakahi Bridge farther down the river. The fossiliferous beds are overlaid by the “marl beds” under the limestone, and the dip of the conformable junction line can be traced from the side of the cliff facing the river round the corner, and up the little creek till it crosses and returns on the opposite bank. This carries us to the road-line, the creek being crossed by a bridge, above which greensands overlie the marly beds. The limestone frowns above, on the right bank of the stream; the greensands and other beds just described pass under the limestone. And again we are satisfied that the Waihao greensands cannot and do not overlie the limestone. The same beds are seen at Waikakahi Bridge; and if the passage of the greensands under the marl is less evident, on account of the junction being in low ground and obscured by the alluvial banks of the river, there is, at least, from what is seen, every probability that they do.

A section on the north or left bank has been given by Professor Hutton (see ante, p. 433). That part of the same section from where the greensands (4) are made to rest on the east end of the limestone ridge (3), and thence across the valley marked “W.B.” on Hutton's section, I sketch below, but subdividing the strata as I read the section in 1880. There is certainly some difference in the rendering, which the reader must try to reconcile if he can.

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North of Arno railway-station the reading of a similar sequence in the same relation of the beds to each other is unavoidable; and the same occurs in the west branch of the Waihao, above the road to Pudding Hill station; and evidence can scarcely have been looked for by those who say there is little evidence to be found, and that little not of a decisive character. No stratigraphy could be plainer than in some of the sections, and the evidence of those that are less clear supports, as far as it goes, that which the others exhibit.

Beyond all question, the greensands underlie the Waihao limestone: and as explanations of the contrary view, islands and fiords without number, crush, faults, contortions, and, in short, all that might render the geology of a district complicated and obscure, are invoked in vain. Not merely do the sections specially examined show this; the general structure of this district, and that of all Southern Canterbury and North-Eastern Otago, points to the same conclusion; and it is rare, almost never, that the Pareora rocks rest on other beds than those of Upper Eocene or Cretaceo-tertiary age. Sir J. v. Haast, in “The Geology of Canterbury and Westland,” points out no instance of their doing so, but says: “The strata belonging to this series lie either conformably upon the Oamaru formation, or, what is still more usual, unconformably upon it.”

I might here stop, and only ask the palæontologists to bend their pliant facts to conformity with the stratigraphical facts; and would have done so, but that I may be expected to say something respecting the nine species of Mollusca that, coming from the Waihao greensands, are said to occur only in Pareora or younger beds. The rest are acknowledged to be fossils of the Oamaru formation. The following is a list of the nine species referred to:—

1.

Siphonalia nodosa, Martyn.

2.

Ancillaria australis, Sowb.

3.

Pleurotoma fusiformis, Hutton.

4.

Pleurotoma buchanani, Hutton.

5.

Pleurotoma awamoaensis, Hutton.

6.

Clathurella hamiltoni, Hutton.

7.

Voluta corrugata, Hutton.

8.

Natica suturalis, Hutton.

9.

Leda fastidiosa, Adams.

10.

Siphonalia nodosa, or a form as like Martyn's species as that which from the Waihao receives the name, I collected from the Whaingaroa clay, Raglan, at the time Mr. Cox's first examination of these beds was made. This is, therefore, a fossil of the Oamaru formation of Hutton.

2.

Ancillaria australis.—All the specimens from the Waihao greensand that could possibly be referred to this species, agree

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badly with specimens now living, and closely resemble A. fusiformis from the Eocene deposits of Britain.

3.

Pleurotoma fusiformis was described from Mount Harris. Von Haast does not mention it as coming from the Waihao greensands. I have collected it often, but not at the Waihao, and think it should be dropped from the list.

4.

Pleurotoma buchanani.—This is mentioned by Dr. von Haast as a fossil of the Waihao greensands. A distinction of the Waihao specimens from those coming from younger formations might be shown, but I choose to admit it a fossil of the Waihao greensands.

5.

Pleurotoma awamoaensis.—This, in the first lists, was given as a variety of P. awamoaensis. Why should it now be otherwise?

6.

Clathurella hamiltoni.—I do not know this species, and accept it as coming from the Waihao.

7.

Voluta corrugata.—That such a prominent fossil in all the beds in which it occurs should be absent from the collections made by v. Haast and myself, leads me to think that the specimen from the Waihao greensands must, in the first list, have been named V. elongata, Hutton. I have a species of this genus from the beds, but it is neither V. corrugata nor V. elongata; therefore, until its occurrence be verified, I cannot accept V. corrugata as a fossil of the Waihao greensands; though, at the same time, I suspect that it occurs in the Oamaru formation.

8.

Natica suturalis comes from Mount Royal, near Palmerston, Otago, where the beds are most certainly the same as those elsewhere referred to the Oamaru formation of Hutton.

9.

Leda fastidiosa comes from beds belonging to the Oamaru formation in the Trelissick Basin; that it is recent, concerns us not at the present time.

Thus, of these nine species, there are only three that can be fairly claimed as being unknown in rocks of greater age than the Pareora beds. Pleurotoma fusiformis is very doubtfully a fossil of the Waihao greensands. Pleurotoma buchanani and Clathurella hamiltoni are, therefore, the only evidences that the Waihao greensands belong to the Pareora formation.

Are the palæontological proofs, then, of such a character that we must disregard the clear stratigraphical evidence as above stated?

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Art. LVII.—Geology of Scinde Island, and the Relation of the Napier Limestones to others in the surrounding District.

[Read before the Hawke's Bay Philosophical Institute, 11th October, 1886.]

Plate XXVII.

In the last volume of the “Transactions,” two very interesting and, so far as they relate to the geology of this district, two important papers, appear on the geological structure of the Napier hills. One of the papers is by Captain F. W. Hutton, F.G.S., Professor of Geology at the Canterbury College, and it is headed “On the Geology of Scinde Island.” The other paper is by Mr. A. McKay, of the Government Geological Department, and bears the title “On the Geology of the Napier Limestones.”

Napier, or, more properly, that portion of it which is known as Scinde Island, has formed for years past a kind of battleground for the geologists; and, if we may judge from the two papers referred to, it is likely to remain so for some time to come. The questions to be decided are: 1st, As to the age and conformity of the Napier limestones; and, 2nd, As to the relation they bear to the other limestones in the surrounding district.

I cannot do better than state in their own words the conclusions arrived at by the authors of the above-named papers, after paying special visits to this district to prosecute their inquiries.

Captain Hutton says (“Transactions,” vol. xviii., p. 329): “The result of my examination is to show that the northern end of the island is formed by the Petane series. This series rests unconformably on the Scinde Island limestone, which forms, with the underlying sandstone, all the southern part of the island.” On page 371 of the same volume, Mr. McKay, after an examination of the Napier beds extending over three days, concludes that “there is an upper and a lower limestone in Scinde Island,” but he sees no reason to suppose that these are unconformable to each other. “To me,” continues Mr. McKay, “the evidence was quite clear that the lower limestones and overlying sands are connected by passage-beds, and shade into one another;” and, further, “that not the northern, but the western side of Scinde Island shows the presence of the younger series.” Nor could Mr. McKay” arrive at the conclusion that the lower beds [of Scinde Island] are the equivalents of the Te Aute limestones, nor of any formation containing no more than 35 per cent of recent species.” I am informed that Dr. Hector agrees entirely with the conclusions arrived at by Mr. McKay, as here quoted.

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It is useless to point out how entirely different are the opinions of these geological experts, and it seems to me that this Society, or at least those members who take an interest in geology, should endeavour to clear up the points of difference as soon as possible.

It is a curious circumstance that each geologist who has written about Scinde Island differs as to the dip of the beds. Mr. Cox* says: “At Scinde Island, Napier, where the typical development of these beds occurs, they are forming a low anticline, dipping on the sea face S. 10°, but on the harbour side N.W. 25°.” Mr. McKay says: “These marls form the west side of the Napier Harbour…the lowest beds exposed on the south-west side of the island …they dip N.E., bringing the limestones to the sea level at the north end of Shakespeare Road.” As Mr. McKay says in his recent paper that there is no unconformability between the upper and lower Napier limestones, and as the marls are certainly not the lowest beds, but are above the lower limestones, I infer that he wishes it to be understood that the general dip of the Napier rocks is to the north-east.

On the other hand, Captain Hutton, in the paper from which I have already quoted, says: “On the south-east side of the island this series [i.e. the Ahuriri series] dips about S.E. 5°. To the northward it gets horizontal, and then dips to the northwest. On the east side, at Curling's Gully, the dip is N.W. 20°, and on the west side, at Taradale Bridge, it is N.N.W. 10°.”

These quotations will serve to show how wide are the differences of opinion between the geologists on a question of fundamental importance, and to me they constitute strong presumptive evidence in favour of unconformability between the Napier series.

The conclusions at which I have arrived with respect to the Napier series are that, exclusive of the comparatively recent surface-deposits of brick and pumiceous clays and sands and ordinary soils, there are three distinct series of rocks forming the Napier hills. These series are unconformable to one another, the lower limestones being succeeded by marls, and the marls by limestones, which in this paper are termed the upper Napier limestones. My reason for arriving at these conclusions will be found in the following evidence:—

In a journey round the base of the Napier hills the following principal alterations in the dip of the beds will be seen:—

Commencing at the junction of Byron Street with Beach Road, there is at this point an important exposure of what I

[Footnote] * “Geological Report,” 1874–76, p. 100.

[Footnote] † “Geological Report,” 1876–77, p. 84.

[Footnote] ‡ “Trans. N.Z. Inst.,” vol. xviii., p. 329.

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venture to say are the lowest of the lower characteristic Napier limestones, in bands of a steel-grey colour and interbedded with yellow and grey calcareous sands and breccia. These beds dip N. by W. at an angle of about 5°. At the junction of Coote Road with Beach Road the rocks forming the bold cliffs along the seaward side of the island are seen to dip to the S.E. at an angle varying from 5° to 10°. Thus, at the point where the prisoners from the gaol carry on their work of stone-breaking, a syncline is observable in the lower beds. Further on, along the beach, the rocks of the lower series dip to the N. by W. at a low angle, in no case exceeding 12°. On the Ahuriri side of the island, at the junction of Hospital and Battery Roads, an anticline is formed by the lower limestones, where they are to be seen dipping N.E. and N.W., at varying angles from 10° to 25°. Along the S. and S.S.E. sides of the hills, extending from the recreation-ground to the starting-point on Beach Road, none but the lower limestones are to be seen—overtopped here and there by marls—and these dip to the N.W. at slightly varying angles, but in no case exceeding 15°. At the places known as Battery Point and Pandora Point, on the west side of the hills, the limestones and sands overlying marls are seen dipping W. and S.W. at an angle of 10°; but near to the large exposure of marls, limestones, and sands belonging to the Railway Department, and locally-known as Scandinavian Point, the lower limestones are just exposed, and are seen to dip to the N.W., or N. by W., at a low angle, whilst the upper limestones have a similar dip to those exposed at Pandora Point.

My own opinion is that the general dip of the lower Napier limestones is N.W., at angles varying from 5° to 25°, and that the oldest rocks exposed in the Napier hills are those seen between the Napier public school and the quarry at the junction of Byron Street and the Marine Parade.

1st. Now, as to unconformability or otherwise of the Napier series.

Captain Hutton says: “The upper limestones in Scinde Island are unconformable to the lower;” whilst Mr. McKay says “there is no unconformability between the upper and lower limestones.” After a detailed examination of the numerous exposures to be seen on and around the island, I agree with Captain Hutton as to unconformability between the limestones; but I am prepared to go a little further by stating that there is unconformability between the lower limestones and the marls which rest upon them, except where denudation has taken place, and between the marls and the upper limestones.

My reasons for holding this opinion are to be found in the following evidence:—

Along the east side of the island, extending from Beach Road on the south to Lyndon's corner, at the Ahuriri end of

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Shakespeare Road on the north, all the principal exposures of the Napier series are to be found. I have already pointed out the existence of a syncline at the junction of Coote Road with Beach Road in connection with the lower limestones. If these limestones are followed along the ocean side from Coote Road in a northerly direction, a marlbed will be seen to make its appearance about half-way between Coote Road and what is locally known as the First Bluff. This marl is exposed about 100 feet above high water-mark, and where first seen is only a few feet in thickness. It is readily distinguished from the overlying beds and from the limestones by its yellowish straw-colour. A little further on the marl thickens out rapidly, but at the point the marl seemingly disappears, and the limestones are overlaid by the reddish-coloured pumiceous clay sands—the loëss, or brickearth, of Hutton. A little further to the north the marl again reappears, and at the highest point in the island, immediately above where the breakwater operations are being carried on, the marl is seen to thicken out, in a distance of not more than 120 yards, from about 15 feet to more than 60 feet, and the upper series of Napier limestones make their appearance, resting, as they do, unconformably upon the marls, and being in their turn overlaid by extensive deposits of brick-earth, pumiceous sands, and black soils composed of vegetable matter, volcanic dust, scoria, and pumice grit. Structurally, the upper Napier limestones are quite unlike the lower ones, and, once seen, their peculiar compact and dark shelly structure is readily distinguishable. At the time when the pumiceous clays, sands, and grits were deposited, it would appear that denudation had washed away a large proportion of the upper limestones and the underlying marls, and that the lower limestones, equally with the marls and upper limestones, had become surface-rocks.

Between Coote Road on the south-east and Taradale Bridge on the south-west the lower limestones have undergone a large amount of denudation, and in one place only is the marl to be found, this being on the town side from the residence occupied by Dr. Hitchings, and nearly opposite Holt's sawmill. Near the Taradale Bridge there is a large exposure of the marls, and the unconformity between the lower limestones and the marls and between the latter and the youngest beds of the upper (?) limestones is well defined. Near Mr. Glendinning's brickyard the upper or higher marls become somewhat sandy in character, as compared with those seen on the east and north sides of the island, and in one place they are overlaid unconformably by a remarkable bed of pure pumice, dipping to the S.S.E. at an angle of about 40°, and occupying the place of the otherwise denuded fossiliferous sands and craggy limestones. This pumice-bed is the one, I imagine, referred to by Mr. McKay, in one of his reports, as underlying the limestones. An inspection of the

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sections a little further to the westward shows that Mr. McKay was in error in this surmise. At the quarry used by the Railway Department, at Scandinavian Point, the marl is at least 50 feet thick; and when the exposure is viewed from the second bridge along the Taradale new road, the unconformability between the different series can be readily distinguished. At this point several new overlying beds make their appearance, being similar to the upper beds at what is known as Battery Point, some half-mile further to the north-west in the direction of Ahuriri. I am doubtful, however, as to whether these new beds belong to the same horizon as the upper Napier limestones, as seen at the Bluff Point, or whether they are the representatives of the limestones as seen on the Pukekuri Hill and the other hills lying between Napier and Puketapu. I am inclined to the latter opinion, because behind Mr. Glendinning's brickyard, immediately E. by N. of the craggy limestones containing pebbles, and which are the highest limestone beds at Scandinavian Point, the dark compact shelly limestones are met with, dipping S. by W. at an angle of about 15°. Where the compact limestone is found, the sequence of the beds in ascending order is—

Marls.

Compact limestone.

Craggy limestone, with nests of broken and loose shells.

Coarse and impure limestone.

At Scandinavian Point the sequence is:—

Limestones (lower)

Marls.

Compact limestone.

Cretaceous sands, with thin beds of coarse nodular sandstone.

Craggy limestones with pebbles.

Fossiliferous sands, with thin chert bands.

At Pandora Point, which is about midway between Scandinavian and Battery Points, the marl appears to be the only exposed rock, but this is true only of the south side of the point. On the north side the craggy limestone is seen to rest unconformably upon the marls, the evidence being quite clear.

At Battery Point the sequence of the rocks exposed is:—

Marls.

Hard compact limestone.

Sands.

Brecciated limestone with pebbles.

Black pebble bed, 12 inches thick.

Sand beds (fossiliferous), with thin chert bands.

Pumice sands.

Clays.

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Here the marls are largely developed, and unconformability clearly exists between the marls and overlying beds. None of the lower limestones are seen at this point. On the Ahuriri or Port side of the island the marls are exposed in one or two places only, one being near the junction of the Battery and Lighthouse Roads, where the anticline appears to which reference has already been made. In several places on the N.E. side of the island, between Curling's Gully and Breakwater Point, the marls are exposed. Near Sturm's Gully they are interbedded with the pale blue sandy clays, similar to the rocks on the western side of the Napier harbour. From their position in the cliffs, I have been unable to obtain good sections at this point, but I hope to do so shortly, Mr. Goodall, C.E., the harbour board's engineer, having promised to render me some assistance in this matter.

Summarizing the foregoing, it appears to me that the lower Napier limestones, if denuded of the marls, upper limestones, and overlying beds, would resemble a wedge in appearance, having the thicker beds facing S.E. and slanting off in a N.W. direction. Upon the irregular surface of this imaginary inclined plane come the marls, of varying thickness, being somewhat sandy above, earthy below, and having their chief development along the east and west sides of the island. The upper Napier limestones have their chief exposures on the east and west. They dip to the south-west, and near Mr. Glendinning's these limestones must be at least 100 feet thick. On the denuded surfaces of the three series come the pumiceous clays, with grits, pumice sands, brick earth, and black soils, which are to be found more or less over the island, and which, I am inclined to think, will be found the Napier equivalents of the Redcliffe and Kidnapper pumice and conglomerate beds.

2nd. As to the relation of the Napier limestones with those of the surrounding district:

With a single exception, the Napier lower limestones are not represented, as far as I can find, among the rocks to the west and north-west of Napier within a radius of fifteen miles. This exception is to be found in the hills on the west side of the inner harbour and lagoon, having Pukekuri, the hill at the back of Greenmeadows Station, near Taradale, on the southern boundary, and the island known as Quarantine Island as the northern. Considered in connection with the limestones covering the hills between Napier and Tiwhinui Hill, a few miles to the south of Lower Mohaka, these limestones form an important link. Pukekuri is a hill 472 feet high, and consequently 140 feet higher than the highest point on the Napier hills. It is mostly composed of marls similar to those exposed on the saddle at the back of Taradale, on the road to Puketapu. Its summit, however, is covered with limestone similar to the

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upper limestones found at Battery Point and Scandinavian Point, containing well-worn pebbles. These limestones do not appear on the old coast hills between Pukekuri and Petane, but they top the hills further to the west as far as Puketapu, and they are seen to overlie the Napier marls which are exposed in a small cutting on the Petane-Puketapu Road, near Alexander's pleasure-gardens. The beds exposed at the place known as Quarantine Island belong to the lower Napier limestones, and are similar to those seen near Mr. Dolbel's brickyard; and it would seem as if Scinde Island were once joined to the mainland in this direction. Between Napier and Lower Mohaka, along what is known as the Napier-Wairoa Road, the whole of the country as far as Waikaari River is covered with limestone. At Tiwhinui (1,289 feet), which is the highest point reached on the Napier-Wairoa Road, the limestones and sands similar to those seen at Battery Point are exposed as the highest beds in the perpendicular cliffs. Underlying them unconformably are light sands and marls similar to the Napier marls, which are here interbedded with the pale blue-clay bands. These are followed by the leda marls (fault?), which rocks, Mr. Cox, in his report upon the country between Poverty Bay and Napier,* places among the cretaceo-tertiaries. The leda marls at Tiwhinui are similar to those that are exposed near the mouth of the Mohaka River, and which are seen dipping S.S.E. at an angle varying from 10° to 20°.

These leda marls form, so it appears to me, the northern bend of a syncline which extends to Patangata, near Kaikora, on the Tukituki River, where the leda marls are seen on the right bank of the river, nearly opposite the hotel, dipping to the N.E. at an angle of about 15°. It is at Tiwhinui, to the north of Napier, and at Patangata to the south, where the limestones are met with resting unconformably upon the lower tertiaries, and it would seem that within this syncline all the limestones, marls, sands, and conglomerates found between Patangata and Tiwhinui must be classed. They rest within the syncline as in a basin, and the Napier limestones occupy almost the central position in the trough of the syncline. The limestones, marls, and sands which are so largely developed on the Tiwhinui, Moaeangiangi, Arapanui, and Tongoio Hills, to the north of Napier, undoubtedly belong to the Napier upper limestones only, as seen at Battery Point and Scandinavian Point. There is no trace whatever of the lower Napier limestones north of Tongoio; but on a small rise about midway between the Maori pahs at Petane and Tongoio traces of the lower Napier limestones are seen, overlaid by marls, followed by a conglomerate bed.

Between Napier and Patangata, viâ Havelock, through what

[Footnote] * “Geol. Report,” 1874–76, p. 97.

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is known as the Middle Track, the marls similar to those at Napier are to be met with among the higher rocks only. The lower rocks are classed by Mr. McKay as belonging to the Te Aute limestones. If such is the case, I venture to disagree with Mr. McKay in his conclusions that “the Napier lower limestones are not the equivalents of the Te Aute limestones.” There is no doubt in my own mind that the limestones behind Havelock correspond stratigraphically with the Napier lower limestones; and I believe that palæontological evidence will shortly be forthcoming to prove the correctness of this statement.

I have purposely omitted all reference to the fossils collected in the different beds to which reference has been made, my aim having been to show, as far as I could, (1) that the Scinde Island rocks are made up of three distinct series, which are unconformable to one other; and (2) that the upper Napier limestones are related to the limestones to the N. and N.W. of Napier, whilst the lower limestones have their equivalents in what have been termed the Te Aute limestones.

Description of plate XXVII.

Fig. 1. Ideal section of Scinde Island, from east by north to west by south:—a. Pandora Point.—1. Lower limestones. 2. Marls and clays. b. Breakwater Bluff.—3. Upper Napier limestones. 4. Pumiceous clays and sands.

Fig. 2. Scandinavian Point.—1. Pumiceous sands and clays. 2. Brecciated limestones. 3. Calcareous sands. 4. Limestone and pebbles. 5. Sands and marls. 6. Compact limestone. 7. Marls and sands (blue paper).

Fig. 3. Breakwater Point.—1. Pumiceous sands and clays. 2. Compact limestone. 3. Marls. 4. Lower Napier limestones. 5. Fault (downthrow). 6. Blue sands (fossiliferous).

Fig. 4. Junction of Byron Street with Marine Parade.—a. Lowest exposed Napier beds, dipping N.N.W. b. (see description fig. 5.)

Fig. 5. Junction of Marine Parade with Coote Road.—b. Showing syncline; c. marls; d. clays and pumiceous sands.

Fig. 6. Battery Point, West of Scinde Island.—1 and 2. Pumiceous clays and sands. 3. Fossiliferous sands (calcareous). 4. Limestone (brecciated). 5. Calcareous sands with nodular chest-band (fossiliferous). 5′. Black pebble bed. 6. Calcareous sands (fossiliferous). 7. Limestone.—compact, similar to 2, Breakwater Point, Fig. 3. 8. Marls and sands.

Picture icon

Geology of Scinde Island

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Art. LVIII.—Notes on the Age and Subdivisions of the Sedimentary Rocks in the Canterbury Mountains, based upon the PalæEontological Researches of Professor. Dr. C. Baron von Ettingshausen in Gratz (Austria).

[Read before the Philosophical Institute of Canterbury, 2nd September, 1886.]

For many years past a great diversity of opinion has prevailed concerning the age and relative position of the Mount Potts beds in the Rangitata River, containing only fossil shells and saurian remains in one, and some plant remains in another, locality, not far distant from each other; and the Clent Hill beds in the Upper Ashburton District, in which only fossil plant remains have hitherto been found.

Whilst Professor McCoy, in Melbourne, as far as 23 years ago, assigned the Mount Potts beds to the Lower Carboniferous or Upper Devonian, and the fossil plants of the Clent Hills to Jurassic times, I always maintained, based upon the stratigraphical relations of those two groups of beds to each other, that they were of the same age, having shown at the same time, and as I hope conclusively, that both occur near the base of the whole series. Since then, the Geological Survey of New Zealand has repeatedly examined these localities, the result being that the shell-beds were first called Liassic, then Triassic, and now Permian; and the plant-beds in the Clent Hills, Jurassic, with which those of the Malvern Hills and some other localities were associated.

The principal point of difference between Professor McCoy and myself on the one hand, and the Geological Survey of New Zealand on the other, was not the real age of the Mount Potts and Clent Hills beds, but the great difference of age assigned to them.

In a paper on the “Geological Structure of the Southern Alps of New Zealand,”* I once more reiterated my views on the subject; and my researches for the last twenty years have amply confirmed this. Dr. Hector, however, has continued to defend his own views, of which his attempted refutation of my paper in the same volume is a proof.

For many years past, together with other New Zealand geologists, I have waited in vain for a reliable description of our fossil plants by a competent palæontologist, so that the data upon which the different views were based could be verified. I

[Footnote] * “Trans. N.Z. Inst.,” vol. xvii., p. 322.

[Footnote] † “Notes on the Geological Structure of the Canterbury Mountains,” etc., l.c., p. 337.

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availed myself, therefore, gladly of the kind offer of Professor von Ettingshausen, an eminent Austrian palæontologist, who has made palæo-botany his special study, to describe our fossil flora, and to bring light into the chaos which hitherto has reigned. I sent to him not only all the fossil plants collected by myself in New Zealand, but Professor Parker forwarded all those contained in the Dunedin University Museum, so that ample material was in the hands of Professor von Ettingshausen to go carefully into the whole subject. This eminent palæo-botanist has just finished his labours, for which he had not only to go repeatedly to Vienna, but had also to pay a visit to London to study and compare the material there.

His paper, illustrated with numerous plates, will appear in the “Transactions” of the Imperial Academy of Science in Vienna, but in the meantime he has kindly favoured me with a short résumé of the results of his labours, of which I hasten to lay a translation before you.

Professor von Ettingshausen states as follows:—

“In the first instance, you will doubtless like that I should place together all the localities according to the flora contained in them:—

To the Trias belong: Mt. Potts, Clent Hills (Haast Gully), Malvern Hills (older series), Mataura, and Waikawa.

To the Cretaceous period belong: Grey River, Pakawau, Wangapeka.

To the Tertiary period belong: Shag Point, Malvern Hills (younger series), Murderer's Creek, Radcliff Gully.

“Now some few observations on the characteristic plants of each locality, and the flora in general:—

Mt. Potts offered only very few distinguishable plant remains. However, I could recognise amongst them with certainty Asplenium hochstetteri, Tœniopteris pseudo-vittata, which belong also to the other Triassic beds. I found amongst them also a Baiera, which confirms the age of the locality as Triassic, A fragment, though rather defective, is doubtless a Thinnfeldia, which again does not militate against such a designation, which however excludes older beds, like Permian for instance.

Clent Hills (Haast Gully).—These shales contain very interesting plant remains, and appear to promise still a greater harvest of valuable things. To the leading and characteristic remains belong four species of Tœniopteris, Asplenium hochstetteri and palœo-darea, Palissya podocarpites and two species of Thinnfeldia. A very peculiar Comptopteris and an Equisetum are closely allied to Triassic forms.

Malvern Hills (older beds).—Tœniopteris, analogous to other Triassic species, Asplenium hochstetteri, Thinnfeldia, a Podozamites,

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and a Pecopteris, are the most remarkable plant remains from this locality.

Mataura and Waikawa.—The Tœniopteridœ, Zamites, Pterophyllum, Nillsonia, altogether in forms analogous to Triassic genera, with Asplenium ungeri, of such universal occurrence, prove the identity with the last-mentioned beds.

Grey River, Pakawau, and Wangapeka contain a flora which is well distinguished from that of other localities of the Cretaceo-tertiary formation, and which decidedly ought to be placed with the Cretaceous formation. However, the material at my command will not allow me to state at present with certainty to which of its subdivisions these remarkable beds belong.

“The flora contains four Filices, amongst them one form, Martensia, specially characteristic of Cretaceous beds; one Dammara; one new genus of Taxinea; four species of Podocarpium; one Dacrydium; one most interesting genus uniting the genera Ginkgo and Phyllocladus; two Gramineœ; one Musacea; one Palma, closely allied to a Cretaceous species; one Casuarinea; three species of Quercus; one Dryophyllum; two species of Fagus, Nemophylon; one genus of Ulnacea, uniting Ulnus and Planera; one Ficus, Cinnamomum haasti, two Proteaceœ; and several Dialypetalæ.

“From the Tertiary deposits, Shag Point and the Malvern Hills furnished the most interesting plant remains.

“The flora contains three Filices, amongst them one form closely allied to European Tertiary species, a Sequoia, closely allied to the European Sequoia couttsia; Araucaria haasti; two species of Dammara; two of Podocarpus; one Dacrydium; one Najadea; one Palma; one Casuarinea; three species of Myrica (!), amongst them one almost identical with a European Tertiary species; one Alnus (!), most remarkably near a European Tertiary form; four species of Quercus; three of Fagus; one Ulmus; one Planera; one Ficus; one Hedycarya; three Laurineœ; one Santalacea; one Protacea; three forms of Gamopetalœ; and several Dialypetalœ.”

I need scarcely point out that this information is very valuable, and will gladly be received by New Zealand geologists; and I have no doubt that, if once in possession of Baron von Ettingshausen's interesting paper, a great step towards the elucidation of many obscure questions in our stratigraphical geology will have been accomplished.

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Art. LIX.—Notes on the Geology of the Bluff District.

[Read before the Southland Institute, 21st January, 1886.]

Now that the Bluff is becoming a sea-side resort to the inhabitants of the district, as well as a place of call, and often of a little detention, to strangers passing to and from the Australian Colonies, it may be interesting to some to know a little of its geology. The first thing that will attract the attention of the visitor who has an eye to the rocks will be the ragged slaty strata standing on edge, and striking N.W. and S.E., exposed between low and high water, and in some places considerably above, and flanking the hill from the pilot station to the jetty. These, according to Dr. Hector, belong to the Devonian period, and to the great series of palæozoic rocks that form the backbone of New Zealand, or, in other words, the axis of the great mountain system extending from Auckland to Stewart Island. On closer examination, these argillaceous slates are seen to be, at least near the jetty, interstratified with bands of syenite, or granite, from a few inches to several feet thick, becoming more granitoid towards the base of the hill, which is a solid mass of syenite. This would almost lead one to suppose that the hill itself had once been a mass of slate formations of similar age, and that it has been granitized by metamorphic action, and that, at the present junction with the slates, the bands of interstratified granite are only the more silicious layers which have become granitized; while the more argillaceous layers have withstood the dying-out metamorphic action.

This appearance Captain Hutton says he is “positive is fallacious,” and holds the opinion that the whole range from the New River Heads to Ruapuke is an immense dyke of intrusive syenite. I am not aware that Dr. Hector gives an opinion on this point; but from the fact that in his Geological Map it is coloured as metamorphic, instead of true granite or volcanic, it would appear that he inclines to this view. It may also be observed here that Mount Anglem, and the northern half of Stewart Island, is also coloured in his map as metamorphic, while the southern half of the island is coloured as true granite, the same as the West Coast. There can be very little doubt, however, that Captain Hutton's view is the correct one, and that both Mount Anglem and the Bluff Range are of volcanic, or at least of eruptive, origin. Conclusive proofs of this are seen in following round the beach from the Bluff to the Greenhills railway-station. For a mile or two the interstratified bands of syenite or diorite are parallel with the slate and the base of the

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hill; but as soon as the range trends to the north, the outlying dykes strike still parallel to the base of the hill, but almost at right angles to the strike of the slates, cutting them transversely, and crumpling and contorting them in every conceivable way, just as a wedge driven into wood transverse to the fibre would bend and crumple the parted ends towards the right or left. Many instances of this are seen where the slate beds are cut at different angles by dykes of syenite, or diorite, from 4 to 20 feet thick, and bent by the intrusion of the latter sidewise in curves, in some instances almost semicircular.

In the débris of these dykes I found two large crystals, apparently of amphibole; one a thick hexagonal prism about 7 inches long, and as much or more in circumference, dark greenish-grey, and rough on the faces; the other about 4 inches long, also hexagonal, but instead of ending in a pyramid its ends consisted of only two planes meeting at an angle of about 60°, but I did not measure it, intending to examine it more carefully at home. This, unfortunately, I was precluded from doing. As they were somewhat heavy to carry, and I had a day's walk before me, I put them aside, meaning to get them on my way home. On my return the tide had risen higher than my calculations, and had taken temporary charge of my crystals; and notwithstanding that I have twice sought for them since, I have not been able to pick them up again.

In these dykes also blade-like crystallizations are not rare, of large size, and sometimes ending in an imperfectly-shaped four-sided pyramid. Small rough crystals are also frequently observable of undoubted hornblende or augite. All these could not have been the result of metamorphism, and prove conclusively that the range itself, of which these are but the outliers, must be a truly instrusive mass.

The age of the syenite, or, in other words, the period of intrusion, is the next question: and this can only be inferred from the characters of the rock itself. In many respects these are quite peculiar. It is heavily charged with sulphides and bisulphides, and so full of magnetite that a piece of the size of the hand will, in many cases, deflect the compass-needle 8° or 10°. The whole mountain is an immense magnet; and, in walking over it, the needle is constantly varying both in declination and dip. Iron is therefore present in far larger quantity than is usual in ordinary granitic rocks. Copper is present in every specimen I have tested, and often in considerable quantity. It is not at all improbable that a workable lode may yet be found of this metal at some of the points of junction with the slate. Manganese occurs plentifully in the detritus on the shore, from the wearing down of the rock by the sea. Black ironsand, auriferous and platiniferous, occurs under the same conditions so plentifully that it has been profitably washed for

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gold. Molybdenum, tungsten, tin, antimony, and arsenic are also found in small quantities in many parts of the range. The great quantity of iron and sulphur alone would argue a younger age than that of ordinary intrusive granite. The argillaceous slate through which it has burst is, as has been said, according to Hector, of Devonian age, and, according to Hutton, of carboniferous; and corresponds in this respect with the formation of Longwood, the Takitimos, Lake Te Anau, and the south of Lake Wakatipu. As there are no fossils, this can only be inferred from the lithological character of the strata. There is, however, little room to doubt that it is at least not younger than the Devonian. The outburst must, therefore, have taken place posterior to this period, but probably at no great distance of time, geologically speaking.

It is probable that the basin of the Southland Plain, now filled up by younger formations, was formed at the time of this outburst, and that the elevation of the Bluff Range was at the expense of Southland, by the extrusion of material in a plastic condition from under the surrounding district. There is evidence to show that strata may become plastic at no great elevation of temperature in many parts of the Hokonui District, in formations ranging, according to Hector, between the Permian and the Cretaceous. In many places, where there is not the least sign of any volcanic agency, patches occur, often not more than an acre or two in extent, of true trap rock full of small round boulders, and rock of a basaltic character, which must have resulted from the ordinary strata becoming plastic through chemical agency, and presenting all the appearances of an incipient volcano on the smallest possible scale.

The Cannon Ball sandstone of the Bastion and the Otapiri (so named by the officers of the Geological Department) seems to have originated in a similar way. If this be so, it is quite conceivable that the ancient strata under the Southland Plain, underlying the great Silurian and Devonian period, had, from chemical agencies, become plastic on a large scale, and, under pressure from the slow evolution of gases, had ruptured the overlying strata that imprisoned the sulphurous semi-fluid mass at the weakest places—in this case, along the line of the Bluff and New River Ranges—and by exuding a great viscid drop-like irregular excrescence, formed, on solidifying and recombination of material, the present range of granitic hills, extending from Ruapuke to the New River Heads.

Whether this hypothesis will fit in with all the facts, or not, must be left to the judgment of observers. It may at least serve till a better is found. Between the Greenhills quarries and the Mokomoko, the slates flanking the syenite are dark-blue, and of a fine compact texture, intersected here and there by veins and dykes of white quartz, which, being in the vicinity of much

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finely-crystallized iron pyrites, are likely to be auriferous in parts. Indeed, alluvial gold can be obtained in small quantities almost everywhere along the flank of the range. The beds are here, as at the jetty, quite perpendicular, and even more contorted and crumpled. As they recede from the range they flatten out to a gradually-decreasing N.E. dip, and change in character to a massive indurated sandstone of a greenish colour, often studded with splendid crystals of iron pyrites that stand exposure for a long time without rusting.

It is in these blue compact slates that fossils are likeliest to be found. I have often seen what I took to be fragments of shells, but have never been able to prove conclusively that such was the case; but from the abundance of lime in the composition of these blue slates it is almost certain that shells were embedded with them, and may still be found where the conditions of preservation are most favourable. They are not so much metamorphosed as might have been expected from their close proximity to the granite, and in some places fossils are quite likely yet to be found. The Bluff Harbour itself seems to have been at no distant date a freshwater lake. The floor of the harbour is a soft bluish-green very friable sandstone, scarcely more than hard-pressed sand with a little clay in it, and highly micaceous. There is not even a spectroscopic trace of lime in it, which must have been the case had it been a marine deposit. There is a good deal of sulphur, as sulphide of iron, which sea-water would have decomposed. There is also timber, quite fresh, and apparently in situ, from the roots being dredged up by the dredging-machine, with the embedding clay still adhering to the curly gnarled roots as naturally as if the tree had been pulled out of the ground on which it grew. The timber dredged up was evidently that of rata (Metrosideros lucida), which is still abundant in the vicinity.

Art. LX.—On the Formation of Timaru Downs.

[Read before the Hawke's Bay Philosophical Institute, 12th July, 1886.]

Plate XXVIII.

Dr. von Haast, in his work on the “Geology of Canterbury and Westland,” p. 367, ascribes the formation of the Timaru plateau to a sub-aerial origin, and compares its structure to the loëss (or loam) deposits of China, the Rhine, and Danube, as described by Baron von Richthofen, the eminent German traveller and geologist, who, he says, “has shown in his last publications

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that the loëss in China could only be of sub-aerial origin, deposited by apnais, which at the present time are still at work in forming that rock. Atmospheric currents, together with the growth of grass and other vegetation, during an untold number of years, are the principal agencies by which the loëss has been deposited. In the first instance, rain water, running down the more or less steep slopes of the country, carries with it fine particles, which are partly retained by the grass or amongst its roots; whilst the wind, blowing across the land, takes up a great amount of fine sediment, afterwards also partly caught and retained by the grass. However, a third and most important agent is to be found in the roots of the plants themselves decaying, and thus raising the ground. There is a peculiar vertical capillary texture observable in the true loëss, deriving, doubtless, its origin from the decaying of numberless rootlets during many past generations of grasses.” Dr. Haast goes on to state, “during the Great Glacier Period of New Zealand, beginning towards the end of the pliocene and ending in the post-pliocene period, during quaternary and recent times, the loëss-beds have gone on accumulating steadily so as to reach such a considerable thickness, as we find them, amongst other localities, as the lower slopes of Banks Peninsula, and on the Timaru plateau.”

This view has been opposed by Professor Hutton, who, in an article on the silt deposit at Lyttelton, laid before the Philosophical Institute of Canterbury,* clearly shows that those deposits do not belong to the loëss formation. After weighing all the evidence he could obtain, he arrives at the conclusion “that the evidence in favour of the marine origin of this deposit preponderates enormously over the evidence in favour of its sub-aerial origin,” including in this judgment the Timaru formation. Not having seen much of Banks Peninsula, I am unable to make any personal remarks on the silt formation there; but with Timaru it is different, as having been resident there for some time, I have had the opportunity to obtain such information as makes me differ from Dr. von Haast as well as from Professor Hutton.

The Timaru Downs are situated to the south of the Canterbury Plains; they are about six miles broad, and extend inland from the sea about ten miles. They consist of gentle undulating country, well adapted for agriculture. The structure of these rolling downs is very peculiar. It is very evident, from abundance of data, that the Canterbury Plains at one time extended all along where these downs now exist, and that actually the plains are there at present (beneath), and that the downs have been built on the plains. The plains beneath the downs have been covered over with beds of dolorite or basalt, and over the

[Footnote] * “Trans. N.Z. Inst.,” vol. xv., p. 411.

Picture icon

Sections Showing Effects of
Two Blasts at Ahuriri Bluff
Napier N. Z.

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dolorite occur beds of fine brownish-yellow material, interlaid with regular streaks of volcanic ash. These beds curve with the hill, and do not occur in flat beds, as in marine deposits. The regular streaks of volcanic ash are very evident in any new cutting, and the pieces of ash can be readily picked out. That dolorite exists below the downs, and resting on the shingle plain, there is ample evidence, as both can be traced up all the deep gullies; and has also been proved from wells that have been sunk, from bores put down, and from quarries. The shingle beneath the dolorite beds shows evidence of having been subjected to great heat, and the dolorite in many places is scoriaceous; in fact, many pieces can be found that could not be distinguished from Auckland (Mount Eden) scoria. Nobody can for a moment doubt but that this dolorite was emitted as lava from some volcano situated above these downs—probably near Mount Horrible. This lava spread over the country in two or three layers, pouring down in ridges. The volcano being spent as to lava, it then, doubtless, belched out ooze and mud, with occasional showers of cinders and ash. The ejected material would overlay and envelope the dolorite beds. There is an excellent section north of Timaru, formed by a railway cutting, showing the dolorite bed, and above it the beds of ooze, with unmistakable layers of cinders (Pl. XXVIII.). In this bed of ooze, deep down, I have found moa bones, but no trace of land or marine shells; and I have not observed the peculiar vertical capillary texture observable in the true loëss, as described by Dr. von Haast. The occurrence of moa bones would tend to prove that these beds were comparatively recently formed, as might be from a sudden volcanic outbreak, and not from a slow formation as that of the loëss, which would take ages, and so reach the time prior to advent of the moa.

I am led the more strongly to uphold the volcanic origin of these downs from having seen very similar formations elsewhere, when there could not be the slightest doubt of their formation. That was in Auckland, during the execution of the Auckland improvement works at Albert Barracks. Heavy cuttings had to be made for the streets, and one of these cuttings went actually into the cinder cone of an old crater. Further away from the cone were similar beds to those at Timaru, with layers of cinders through them.*

There is a peculiar feature in these downs which is a puzzle to all, and that is the occurrence of small lagoons or shallow ponds on the brows of the hills. Almost invariably, as you mount a hill you will find a lagoon on top. Had these lagoons only occurred anywhere else, they would not have caused any

[Footnote] * A drawing of this in section can be seen in the “Trans. N.Z. Inst.,” vol. vii., p. 144.

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attention; but, occurring as they do, it does seem strange how they could have been formed. The only suggestion I can offer to explain this circumstance, is that—having adopted the volcanic theory in the formation of these downs—immediately after the lava or dolorite beds were spread over the country, the mud and ooze were deposited on them. The great heat of the beds—greatest when thickest—would for a long time keep the mud boiling, and so a quantity of solfataras or mud volcanoes would be formed, and when the whole cooled a shallow basin would be left where they existed.