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Volume 9, 1876
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Art. IX.—The Building Materials of Otago.

[Read before the Otago Institute 5th September, 1876.]

Limes, Cements, and Aggregates.

Properties of Cementing Materials.

Before proceeding to treat in detail the native productions, it is necessary to consider the properties of limes and cements generally. In doing so, I should begin by stating that the terms “Lime” and “Cement,” although always used to denote different and distinct articles, are applicable

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to either of them. The cementing ingredients are the same in both cases, the only difference being in the proportions in which they occur. Pure lime is practically worthless for building purposes; it never acquires the necessary cohesive strength in any situation, and never hardens at all in a damp place. In order to make good mortar the limestone must contain a mixture of clay—the proportion varies from 8 per cent. in ordinary building lime to 35 per cent. in strong hydraulic cement. If it were necessary to have a clear dividing line between limes and cements, the best place to strike it would be at the neutral point where the adhesive and cohesive forces are equal. The particles of rich and moderately hydraulic limes adhere more readily to a foreign substance than to each other, but the conditions are reversed with strong hydraulic limes and cements. This gives the only tangible difference I can imagine between the two articles, but as it does not admit of a practical application, the distinction would only be valuable from a scientific point of view.

Limes and cements are usually divided into four classes, according to their properties and strength—

1st.

The Common or Rich Limes that contain less than 10 per cent. of clay or other impurities.

2nd.

Poor Limes, in which the impurities consist of from 10 to 25 per cent. of sand or other insoluble ingredients that will not enter into chemical combination with the lime.

3rd.

Hydraulic Limes, such as contain from 10 to 30 per cent. of alumina and soluble silica.

4th.

Hydraulic Cements, containing from 30 to 40 per cent. of alumina, soluble silica, and other impurities.

In addition to the ingredients named, each of the above classes frequently contains small quantities of iron, manganese, magnesia, potash or soda, with sulphuric and other acids, which do not seem to have an injurious effect on the cementitious properties of the article; on the contrary, some of them, such as iron and soda and some of the acids, are always present in the best cements;—the quantity, however, of all foreign substances, except silica and alumina, seldom exceeds 5 per cent. We may therefore assume, shortly, that our mortars are simply lime and clay in varying proportions.

As already stated, the common or rich limes are comparatively useless where strength is required, and absolutely worthless in a damp situation. They are easily burned and slaked, swell to a great extent in slaking, shrink in drying, and are soluble in water when set. Their adhesive properties are stronger than their cohesive ones, consequently they cannot be used without a large admixture of sand. It is common to hear the expression that

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mortar is injured by too much sand, but the chances are that its bad qualities are the result of the opposite condition, and, above all that, the sand and lime are not properly mixed. If greater care was exercised in this behoof, so that an approach could be made to the theoretical maximum of an atom of sand between each atom of lime, the result would be an immediate doubling of the strength of rich lime mortar.

Poor Limes possess all the bad qualities of the rich ones, and have an additional drawback in irregularity of consistency through not slaking so readily, which necessitates grinding.

Hydraulic Limes are frequently sub-divided into three or four sections, ranging from slightly to eminently hydraulic, the former being practically a rich lime, and the latter a cement. These limes do not slake readily, nor do they expand much in the process. The higher kinds slake so slowly and so imperfectly that they are always pulverized by grinding. Hydraulic limes set under water in from three to fourteen days, according to the strength of the sample.

Hydraulic Cements cannot be slaked by water in the usual way; they are, properly speaking, not calcined, but vitrified. The produce of the kilns resembles slag from a blast furnace, and it requires the aid of stone-breakers, iron rollers, and French burr mill-stones to convert it into the cement of commerce. In common with the higher kinds of hydraulic lime, cement does not require any admixture of sand to make it into mortar; the maximum strength is obtained by using it in a pure state. Some hydraulic cements set under water in a few minutes, but the best kinds take a few hours. In seven days the latter attain a tensile strength of 250 pounds to the square inch.

The quality of limestones cannot be determined by a knowledge of the geological formation in which they occur, nor by their general appearance. Hydraulic limes are perhaps more plentiful in what may be called the mediæval rocks—cretaceous to carboniferous—than in any others; but, as they are frequently met with in the formations above and below those named, we may give them an almost universal range of locality. The character of the stone seems to be determined chiefly by its immediate surroundings—the outer beds are argillaceous or silicious, according as the adjoining stratum is clay or sand, and the whole rock is influenced by the manner in which it was deposited, and the subsequent changes to which it was subjected. If the lime had been deposited in still, clean water on a rocky bottom, and had attained a considerable degree of hardness before being disturbed by convulsions from below, or pressure from above, we might expect it to be comparatively pure; but if deposited in an estuary where the water is muddy and the bottom soft, and where floods leave

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occasional beds of silt and sand, the stone cannot fail to contain impurities. Even after the deposit has taken place the stone may be altered by mechanical and chemical agencies, there being a peculiar relationship between the lime and clay in hydraulic limestone that seems to be easily affected by external causes. A good illustration of the influence of its surroundings on the character of the stone is found at Mr. Macdonald's quarries, Otago Peninsula. The rock is much shattered, and divided into large blocks by “backs” running through it in all directions. The blocks in one of the beds produce two distinct varieties of stone, the analyses of which are given in. Nos. 13 and 15, Table III. The light-coloured stone occupes from two to three feet of the outside of the block, and gradually merges into the dark one which composes the heart;—they vary little in consistency, but, as will be seen from the table, there is a great difference in their composition. Assuming the block was originally homogeneous, of which there can be little doubt, we find that the crust has lost 4 per cent. of carbonate of lime and 2 ¼ per cent. of carbonate of magnesia, while, on the other hand, it has gained 2 per cent. of iron in addition to the increased percentage of silica and alumina due to the abstraction of the lime and magnesia.

Hydraulic limestones are generally compact in texture and dark in colour, grey, blue, drab, or brown being the prevailing colours; white indicates pure lime. It does not, however, follow that all the dark-coloured limestones are hydraulic, for they may contain sand and other insoluble matters that neutralize the effect of the clay; and the darkest of all limestones—black marble—is almost pure carbonate of lime. Still, a rule may be established in a negative manner by saying that no white limestones produce hydraulic lime.

Notwithstanding the advance made in all the practical sciences within the last few years, there is still a doubt as to the causes that produce the setting and hardening of lime and cement mortar. The old theory was that all mortars hardened by the absorption of carbonic acid from the atmosphere, and it was supposed that in time the quantity absorbed would equal that expelled in burning, so that the mortar would revert to its original carbonate, and become again a limestone. It is true that rich limes will not set without carbonic acid. The mortar in the inside of a bastion at Strasbourg was found, after 160 years, to be quite soft, and the same thing was observed in a masonry pillar, nine feet in diameter, at St. Peter's, Berlin, its age being 80 years. It has also been found by experiment that a mortar of rich lime will not set in the exhausted receiver of an air pump. But carbonic acid alone will not perfect the hardening process, consequently it is supposed to be assisted by the crystallization of the carbonate of lime between and around the particles of the aggregates.

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Without such extraneous aid it is difficult to account for the hardening of mortar in thick walls. The operation proceeds from the outside, consequently every advance made is a barrier to the next in so much that it excludes the air from the softer mortar inside. There is every reason to believe that hydrate of lime, when exposed to the atmosphere, will revert to its original carbonate; but the process is such a slow one that it may be almost classed with the geological epochs. The oldest mortar in the world, that from a Phœnecian temple in Cyprus, is still far short of the ingredients it possessed when a limestone.

The induration of hydraulic mortars is attributable in a small degree to the same causes as affect the rich ones, but principally to the formation and crystallization of complex silicates of lime and alumina, the precise nature of which is imperfectly understood. It is quite evident that the absorption of carbonic acid has very little to do with the setting of hydraulic mortar, for against its slow action already noticed we have the fact that large blocks of cement concrete harden uniformly to the consistency of stone in a few months under water, which proves that the setting property is inherent, and not the result of external influences.

The treatment they receive in burning has a considerable effect on the quality of limes and cements of all kinds, but more particularly on those that are only moderately hydraulic. Under burning has been known to impart a spurious hydraulicity to rich limes, and over burning occasionally destroys that property in cement, but as a rule there is little trouble in obtaining maximum results with these extreme classes. The burning of hydraulic limes is a much more delicate operation, the niceties of which can only be acquired by long experience in the art generally, and considerable practice with the actual materials that are to be operated on.

As already indicated, the ordinary aggregates are essential to the induration of rich limes, but in the higher hydraulic varieties and in cement they are simply diluents. As rich limes do not possess the faculty of expelling any excess of moisture with which they are in contact, it is advisable to employ a porous aggregate, such as the sands produced by aluminous and calcareous rock, but when the aggregate is only employed to weaken the mortar by making it go further, there is little danger in using hard silicious sand, provided it is free from earthy impurities; indeed, this is an indispensible condition in all aggregates. It has been ascertained by experiment that the best proportion of sand for rich limes is 2 ½ to 1, and for ordinary hydraulic limes 1 ¾ to 1. This explains the partiality of builders to rich limes. It will, in their own phraseology, “carry more sand,” which means that strength and comfort are sacrificed for an insignificant saving in cost.

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In order to institute a comparison between the various articles under discussion, I give the following table of tensile strength per square inch in pounds on limes, cement, and mortar one year old.

Cement and Limes neat.

Portland cement 500 pounds
Roman " 185 "
Good hydraulic lime 170 "
Ordinary " " 120 "
Rich lime 40 "

Mortars.

Portland cement with 1 of sand 310 pounds
" " " 2 " 205 "
" " " 3 " 140 "
" " " 4 " 100 "
" " " 5 " 50 "
Good hydraulic mortar 140 "
Ordinary " " 85 "
Good mortar of rich limes 50 "
Bad " " " 20 "

Geographical Distribution.

It was shown in a former paper that limestone as a geological formation occupies an immense area of Otago, but it does not follow that the supply of lime for industrial purposes is equally extensive, many of the calcareous rocks being incapable of producing lime of good quality. There is, however, no scarcity of lime suitable for building and agricultural purposes throughout the province. It is known to exist in considerable quantities in the following districts:—Oamaru, Otepopo, Waihemo, Maniototo Plains, Waikouaiti, Lower Harbour, Peninsula, Waihola, Waimea, Winton, Aparima, Waiau, and Wakatipu. These localities are so widely dispersed that we may safely calculate on a supply being available for any demand that can arise.

The only natural cement hitherto discovered in Otago is the well-known Septaria or cement boulders of the Moeraki district, which resemble in every respect the English stones from which Roman cement was originally manufactured. According to Dr. Haast, the boulders follow the coast from Shag Point to the Terapupu Creek, then run in a straight line to the Little Kiwi Creek, which is struck at a point about half a mile from the sea. In the first four miles the deposit is a mere line of boulders lying on the beach or imbedded in the cliffs, but on leaving the coast it expands into a belt from 20 to 30 chains wide and 5 ½ miles long.

Many of the volcanic clays that exist in such profusion along the sea board from Saddle Hill to Oamaru possess cementitious properties similar

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to the Pozzuolanas of Italy and the Tyrass of the Rhine, but as they are only used in combination with lime, they will be considered along with the other aggregates, or as a component part of artificial cements.

The aggregates proper consist of shingle, gravel, and sand, which have an almost universal distribution throughout the province.

Tables of Analyses.

The subjoined tables Nos. I. to IV. give the analyses of the principal lime and cement stones hitherto discovered in Otago, together with English and foreign types. They are arranged into the four classes already referred to, viz., 1st, Rich Limes; 2nd, Poor Limes; 3rd, Hydraulic Limes; and 4th, Cements. A large number of the analyses of Otago stones are from the Jurors' Report of the New Zealand Exhibition and the publications of the Colonial Museum, but all the recent ones are by Professor Black, to whom I am very much indebted for assistance in investigating this subject. Under his direction fifteen analyses of limestones and clays were made specially for the purpose of this paper by Mr. P. S. Hay, B.A. These analyses were done with great care and accuracy, and in the most exhaustive manner, consequently they form a valuable contribution to our information on one of the most important colonial resources.

Rich Limes.

The English and foreign types given in Table I. comprise eight examples that range in purity from statuary marble, a pure carbonate of lime, to the carboniferous limestone of Whiteford in Wales, that has ten per cent. of impurities. It will be observed that ordinary white chalk approaches next to marble in purity, it only contains ½ per cent. of foreign ingredients.

Analyses are given of fifteen Otago limestones that furnish rich limes, which shall now be considered seriatim.

No. 9 is a white, compact, crystalline stone from Southland, locality unknown, probably Winton. Its constituents are 98.80 per cent. of carbonate of lime, and 1.20 per cent. of soluble silica. It is thus entirely worthless as a cementing material.

No. 10. A compact crystalline stone of faint yellow colour from Winton, evidently closely allied in all its essential properties to the preceding one, and equally deficient in cementitious qualities. I believe that these two specimens are fair samples of the stone in the vicinity of Lime Hills, Winton, of which there are about 1000 acres.

No. 11. Fossiliferous, compact, and very hard stone of a dirty yellow colour, from Kakanui. This specimen was analyzed by Professor Black for Mr. Cairns. It contains 98 per cent. of carbonate of lime and magnesia, and 1 ½ per cent of sand, consequently must be placed in the same category as the Southland limes. The stone is burned extensively for building

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purposes, so I am sure the houses in which it is used cannot be very dry.

No. 12. Yellow fossiliferous stone from the Oamaru district, the precise locality “unknown. It is referred to by Dr. Hector as a stone largely employed by Mr. Hutcheson for burning into lime. From the analysis and description given it must be closely allied to the preceding specimen.

No. 13. Soft fossiliferous stone from the eastern side of Waihola Gorge, white in colour, granular in texture, and very absorbent. This is not so abundant nor so much used as the hard variety No. 16.

No. 14. Yellow lithographic stone from the Oamaru district. It has all the external appearances of a lithographic stone, but does not exist in large quantities; it is found associated in the same rocks with No. 12.

No. 15. Grey and yellow travertine limestone of a porous texture from the Dunstan Gorge. This stone, which is sometimes called calcareous spar, is formed by the deposition of lime held in solution in the water of streams and springs. The water acquires the lime in flowing over or through rocks containing this mineral, and it is deposited in concretionary masses on the banks. Travertine is found in the small creeks that flow into the Clutha and Kawarau rivers between Clyde and the Shotover. This stone was first burned for lime in 1864, when it was used in the masonry of the Gentle Annie Bridge.

No. 16. White, compact, and very hard stone from Waihola. This is the stone from which the well-known Waihola lime is produced. It exists in large quantities in available positions on both sides of the gorge through which the railway runs. The rock is very much shattered and dislocated, few of the horizontal joints being more than six inches apart. This facilitates quarrying and breaking, and to some extent balances the excessive hardness, which otherwise would be a great barrier to cheap working. I regret that the Waihola limestone cannot be pronounced good, as, from its favourable situation, it would be an immense boon to Dunedin and the surrounding districts. The limestone contains 94 ½ per cent. of carbonate of lime, which is decidedly too rich for building in a damp situation, or where strength is required. This, and analysis No. 13, by Dr. Hector, are copied from an old advertisement of Dr. Croft's; they refer to specimens taken from the eastern side of the gorge, but I believe the stone now used, on the western side, is equally pure with No. 16. Indeed, it was lately stated in the papers that it contained 98 per cent. of carbonate of lime, which, if correct, makes the matter still worse.

No. 17. Grey granular stone from Oamaru, found in the same locality as Nos. 12 and 14. It contains 2 ½ per cent. less carbonate of lime than the former, and is therefore so much better in quality.

No. 18. Bluish-grey compact stone from Dowling Bay. This is a

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sample from the top seam. Although a rich lime it contains small quantities of all the ingredients that give hydraulicity with little sand, consequently it will make fair mortar for ordinary work in a dry situation. It forms one of five beds of limestone that occur at Dowling Bay, Lower Harbour, the particulars of which will be given further on.

No. 19. Fawn colored, incoherent, and absorbent stone from Aparima, in Southland. It contains 92 per cent. of carbonate of lime, and 5 ½ per cent. of insoluble matter, the precise nature of which is not stated. As the chances are that this is not all sand, we may pronounce the sample a good lime of its class.

No. 20. Compact grey stone from Fews Creek, Lake Wakatipu. According to the analysis, this sample contains 4 ½ per cent. of insoluble matter not defailed out, but Dr. Hector, says that this consists of black sand, iron pyrites, and bituminous matter, in which case the quantity of sand must be inappreciable. The stone will yield lime suitable for ordinary building purposes in the dry atmosphere of the Lake district in which it occurs. Another specimen of stone from this locality was analyzed by Professor Black, with the results given in item No. 16, Table II. It contains 12 ½ per cent. of sand, so I had no hesitation in putting it in the class of poor limes. There is nothing strange in the discrepancy between the two analyses. They may both be correct, although the samples had been collected within a few feet of each other. Impure limestone deposits all over the world have the same character of irregularity in composition between the various strata. The difference may therefore be accepted as a favourable indication of the quality of the Wakatipu limestone. In all probability the intermediate beds will produce strong hydraulic limes. In his “Geology of Otago,” Captain Hutton estimates the thickness of the calcareous deposits in the vicinity of Fews Creek at 600 feet, and reports the existence of similar rock at Afton Burn, on the west side of the lake, and at Stoney Creek, on the Upper Shotover.

No. 21. Bluish compact stone from the Horse Range. This stone belongs to the higher class of crystalline limestones, such as partake of the character of marbles; indeed, it merges into true marble in many places. The deposit occupies a large area of the western side of the range, near Palmerston, in accessible situations for working. With proper treatment this stone would yield a lime suitable for the ordinary purposes of the house builder. The analysis shows a deficiency of alumina, which indicates slow setting, but its ultimate induration is not thereby affected.

No. 22. Grey shelly limestone from Southland, locality unknown. Although the analysis is not complete, it shows this to be a very good lime of its class, probably the best hitherto discovered in Southland.

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No. 23. White granular stone from the Oamaru district. This is the well-known building stone. So far as can be judged from the analysis, it would furnish a much better lime for building purposes than the stone usually burned in the locality.

Poor Limes.

Table II., which gives the analyses of two foreign and nineteen Otago stones that furnish poor limes, is introduced more for the purpose of showing those that are to be avoided than as a basis for the consideration of their properties. It will be observed that with the exception of No. 16 from Wakatipu, all the stones contain upwards of 20 per cent. of silica in the form of sand, consequently their character as poor limes is fully established. The great majority of the samples are from what may be termed the Caversham stones, varieties of which occur at Waihemo, Waikouaiti, Upper Harbour, and Kaikorai. No. 12 is a portion of a Moeraki boulder analyzed by Professor Black, and found to contain 21.00 per cent. of sand. No. 18 is the grey building stone that overlies the white limestone on the eastern side of Waihola Gorge. Although objectionable in a cementing material, the excess of sand is an advantage when the stone is used for building purposes. It is worthy of note that instead of being black as might be expected from the appearance of the stone, the sand it contains is found to be pure white. No. 16 above mentioned is a compact dark stone from the same locality as No. 20 in the class of rich limes. It has been referred to at some length in considering the properties of the latter, but I might add that possibly the presence of 12 ½ per cent. of sand is not sufficient to neutralize the other good qualities. If it were entirely absent the composition of the stone would resemble that of the English ones, which yield quick setting Roman cement.

Hydraulic Limes.

I now come to the consideration of the most important branch of my subject, that of hydraulic limes, and in doing so you should be reminded that its importance does not arise from the simple fact that the lime has the faculty of hardening under water. That is mainly useful in being the test by which the character of the material is established. In displaying this property we know that it is an hydraulic lime, and as such possesses a certain degree of strength and certain powers of resisting moisture, which render it infinitely superior to the richer sorts. Even now, when the manufacture of Portland cement has reached a high stage of perfection, we find the blue Lias limes of England used in the Liverpool docks, and on the other hand no building of any pretentions to stability or comfort is erected with common or rich mortars. Hydraulic lime is therefore more capable of universal adaptation than any other cementing material we possess.

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Table III. gives the analyses of three English and seven foreign limestones that yield hydraulic limes of varying strength. The former are from the blue Lias limestones, an extensive geological formation that extends diagonally across England from Dorset to York. They are undoubtedly the best in the Old Country, and have been extensively used in all the principal engineering works there. The Eddystone and Bell Rock lighthouses were built with a mortar of Aberthaw lime (No. 2) and Pozzuolana. The blue Lias lime of Lyme Regis (No. 5) was used in the London docks, and that from Holywell (No. 10) is still preferred to cement at the Mersey docks, Liverpool, where it is made into mortar with two of sand and one-third of smithy ashes. Recent experiments show that this mixture is only a tenth weaker than Portland cement mortar made with three parts of sand, which is the usual proportion for similar work. Although not shown directly by the analysis, Professor Black calculates that the Holywell stone contains about nine per cent. of silica in the form of sand.

The best known of the foreign hydraulic limes in the table is the Theil stone from Ardiche, in France (No. 4). Perhaps there is no other hydraulic lime in the world that has been so much used in exposed marine works as this one. The harbour works at Algiers, Marseilles, and Port Said all bear testimony to its high character. It has been 20 years in the sea at Algiers without showing symptoms of deterioration; and Mons. Vicat, the great French authority, said that Thiel limestone was the only one he knew that would unquestionably yield a mortar indestructible in salt water. The cementitious properties of this lime have been subjected to a severe test at Port Said breakwater. It is used with fine sand in making large concrete blocks like those at Oamaru. Sand of this kind by itself is not a particularly good aggregate, and the blocks have to stand very rough treatment, as they are thrown into the sea, instead of being lowered gently by machinery. My apology for referring to these foreign materials at such a length is that we have hydraulic limes in Otago that are, so far as chemistry can determine, identical with them in all their essential properties. In fact there is no difference in the composition of the two articles, the discrepancy in the analysis being in all cases within the limit of error claimed by the best analytical chemists.

No. 11. Yellowish white conglomerate stone of a hard compact texture, found 3 ½ miles south of Oamaru. Dr. Hector's analysis is not quite exhaustive, as the soluble silica is not estimated. It is evident, however, there must be a certain quantity of that base in combination with the alumina, in which case we may assume the lime to be feebly or moderately hydraulic. I have no information as to the exact locality of this deposit, nor as to whether it is used for mortar, but I have no hesitation in pronouncing

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it the best lime for building purposes hitherto discovered in North Otago. It is very much superior to the lime in common use from the Kakanui kilns.

All the other Otago limestones in Table III. are from the Peninsula and Lower Harbour Districts; they seem to be members of one large deposit that extends from Seal Point, on the southern side of the Peninsula, to Dowling Bay, on the northern shore of the Lower Harbour. It is near the surface from the ridge south of Mr. Macdonald's kilns to the gully at Harbour Cone; appears again at the head of Hooper's Inlet, and for the last time on Mr. Dodson's property in Dowling Bay, right across the harbour. The breadth of this reef or dyke is unknown; probably it is not more than half a mile, and the aggregate thickness of the seams now visible is at least 70 feet. There are five or six distinct beds of varying quality and depth; as a rule they are well defined, particularly near the upper and lower sides, but occasionally more than one kind of stone is found in the same stratum. Mr. Macdonald, of the Peninsula kilns (the highest on the reef), only counts four beds, while Mr. Robertson, of the Glenmore kilns (which are situated on a much lower level), shows six tolerably distinct specimens from as many different layers. Two of them are, however, so thin that they can scarcely be called beds, and it is also quite possible that they exist in a less marked degree in the upper quarry. There are five well defined seams at Dowling Bay, four of which have been analyzed, viz. —one, two, three, and five, counting from the top. The fourth, which is 20 feet thick, was partially analyzed, but, being found to contain 28.18 per cent. of sand, it was useless to proceed further. Whether regarded as to structure, consistency, general appearance, or chemical composition, these Otago rocks exhibit all the peculiarities of hydraulic limestones of no mean order. Still, as the best authorities recommend a practical test also, I applied it, and the result is equally satisfactory. Mr. Macdonald, at my request, kindly burned samples of what I considered hydraulic stone. As was expected, the lime would not slake in the usual way, and it was pulverized by grinding in a chaff-cutter and sifting through a cloth. In consequence of other engagements I could not complete the experiments at that time, so the lime lay for eight months in a state of powder, which is not calculated to improve its setting properties. There happens to be a parcel of English blue Lias lime at present in Dunedin, so I tested it and the ordinary rich kind from Waihola along with the hydraulic sample from the Peninsula. All the three kinds were submitted to the same treatment and tested together. They were made into mortar neat, and with a mixture of two parts of sand; one set was left to dry in the air, and the other placed at once in water. So far as could be determined by mere inspection, the action of the indurating process was parallel in the English and Peninsula

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limes; perhaps it was a little more energetic in the former, but the difference, if it did exist at all, was scarcely perceptible. The wet samples of unmixed limes had expelled the surplus water they contained—which is what is technically known as having “set”—in three days, and in fourteen days they had acquired the consistency of soft bricks. The pure samples in air hardened without cracking, and were comparatively insoluble in water on the fourteenth day. On the other hand, the Waihola limes in water never set at all; they were softer on the fourteenth day than when immersed, the pure sample in the air cracked and crumbled in setting, and all the air samples were quite soluble. The above results, taken in connection with the chemical test, place this sample of the Peninsula limes in the class of eminently hydraulic, as fixed by the best authorities.

Nos. 12 and 13. Dark fawn, compact stone, analyzed respectively by Drs. Hector and Black, are evidently the same article; it occurs associated with No.15 in the second highest bed at Macdonald's quarries. As will be seen from the table, this stone resembles closely the blue Lias of Aberthaw, in Wales, their essential constituents being as follows:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Aberthaw Stone. Peninsula Stone.
Carbonate of lime 86.20 86.05
Clay 11.20 11.67

The Otago specimen has 2 ½ per cent magnesia in addition, but this is not a fault. Mr. Armstrong informs me that the dark Peninsula stone resembles in appearance the hydraulic limestone of Burdie House, in Midlothian.

No. 14. Drab granular stone from the lowest seam at Dowling Bay. This corresponds in quality with the second highest bed at the Glenmore quarries on the Peninsula, of which Professor Black made a partial analysis. It should yield a very good hydraulic lime, for although it may be somewhat deficient in the ingredients that ensure hydraulicity, it is absolutely free from those that are supposed to have a contrary effect.

No. 15. Fawn-coloured compact stone from the second highest stratum at the Peninsula kilns. The resemblance between this and the famous Theil limestone of France is very remarkable, as will be seen from the following abstract of their principal ingredients:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Theil Peninsula.
Carbonate of lime and magnesia 82.36 82.03
Clay 14.90 14.29
Oxide of iron 1.70 2.80
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No. 16. Yellowish compact stone from Portobello, analyzed by Dr. Hector. The exact locality is not stated, but in all probability it is from the Peninsula or Glenmore quarries. A partial analysis by Professor Black of the lower seam at the latter place gives precisely the same quantity of carbonate of lime. The proprietor says that 22 feet of this bed has been laid bare without coming near the, bottom. Although not shown in the table, there is little chance of much deleterious matter being in this stone. So it may be set down as capable of furnishing very good hydraulic lime.

Nos. 17 and 18. Specimens of compact stone from the top seam at Macdonalds and the third at Dowling Bay. Although somewhat different in colour, these stones are almost identical in composition, and, as will be seen from the following statement, they resemble closely the hydraulic limestones of Lyme Regis of the Dorsetshire Lias:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Lyme Regis Stone. Peninsula Stone. Dowling Bay Stone.
Carbonate of lime and magnesia 79.20 79.95 79.67
Clay 17.30 16.54 18.89

Nos. 19 and 20. Fawn-coloured stone from the third seam at Dowling Bay, and the lowest at the Peninsula quarries. These again are practically the same, and they find an English prototype in the blue Lias of Holywell. Judging from the analyses, the products of this bed might fairly be called cement stones. They are in the highest class of hydraulic limestones, and seem to have all the attributes of a natural Portland cement. Their points of resemblance to the English materials are shown in the following table:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Raw Material of Portland Cement Holywell Stone Dowling Bay Stone. Peninsula Stone.
Carbonate of lime and magnesia 69.87 72.90 71.20 71.72
Silica 20.54 20.10 19.18 18.85
Alumina 3.49 3.52 4.54 5.26
Iron 4.44 2.21 1.99 3.29
Insoluble in hot acids 25.27 23.70 22.80

But if we carry the comparison further, it will be seen that there is a still greater affinity between the English and colonial articles. There is less than ¼ per cent. difference between the quantities of magnesia in the Dowling Bay and Holywell stones, and only a tenth per cent. difference in oxide of iron between the latter and the Peninsula one. The seam of this stone at Dowling Bay is 20 feet thick, and there are also immense quantities on the Peninsula. The rock appears to be perfectly homogeneous, so there is little danger of irregularity in burning when once the proper temperature

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has been ascertained. If the qualities of this stone come up to my expectations, of which I have little fear, the value of the discovery to the community at large can scarcely be over-rated, and from the researches that have been made, I am confident any failure that may take place will result from improper manipulation, and not from a defect in the raw material.

Hydraulic Cements.

Hydraulic cements, the fourth and highest class of material in the scale, is poorly represented in Otago. The only specimen hitherto discovered is the Septaria of Moeraki, and this is very much inferior to the two hydraulic limestones last described. In fact, they should exchange places; properly speaking, the cement boulder is a limestone, and the limestone a cement rock. The present arrangement is adhered to simply because it corresponds with a time-honoured English custom. Although there are so few colonial articles to be described under this head, it does not follow that such will always be the case, I therefore give twelve analyses of English and foreign cements in the raw and manufactured states; they may be useful for reference in case further supplies of native cements are discovered. Sep-tarian nodules or boulders have been used since the beginning of this century in the manufacture of Roman cement; they are found along the south and eastern coasts of England, from Weymouth to Lowestoft, and at several localities inland. There are also solid masses of similar stone at Harwick, in Suffolk, and Calderwood, in Lanarkshire. The Septarian boulders are well dispersed over the Continent of Europe, and cement rock occurs in France and the United States of America. That of Boulogne, in France, approaches next in quality to the artificial Portland cement; it is found in a thick stratum 160 feet below the Septarian beds, and is sufficiently soft to be excavated with pick and shovel.

There is comparatively little risk in manufacturing cement from a solid homogeneous stratum of the raw material, but it is almost impossible to get uniform results from Septaria; a glance at one of our Moeraki boulders is sufficient to demonstrate this. It will be seen that the core is almost pure lime, and the exterior of the ball nothing but clay, while in many cases the quantity of lime is equal in different sized boulders. Dr. Hector analyzed the whole mass of the nodule, including the calcareous veins, and found it to contain 72 ½ per cent. of carbonate of lime, but freed from the veins the yield of lime was only 59 per cent. The stone in No. 13, Table IV., should furnish an eminently hydraulic lime, but the produce of No. 12, Table II., which Professor Black says is a fair representative of the Moeraki boulders, would be a poor lime of very inferior quality.

Practical experiments made with cement from Moeraki boulders are equally irregular and unsatisfactory. Mr. J. T. Thomson manufactured a

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considerable quantity in 1868, and tested it against Portland cement in the following manner:—Two bricks were laid together with mortars of the two cements, and kept a month in water and a fortnight dry. The highest results obtained were, with Moeraki mortar, three to one, and Portland, one to one. It took 400 pounds in both cases to tear asunder the bricks. Assuming they were placed crosswise, this would give a tensile strength of 22 pounds per square inch. About the same time Mr. G. M. Barr got an unmixed sample that stood 150 pounds in 24 days, against 110 for Portland cement under the same conditions. These comparisons are not, however, fair to the imported article, as the samples tested must have been of a very inferior quality. Instead of 25 pounds in the first experiment, ordinary Portland cement should have stood 140, and instead of 110 in the second, the resistance should have been 270 pounds. Mr. John Macgregor also tested the Moeraki cement, but the result was less satisfactory than either of the above. Two samples of mortar were made with pure cement and salt water—one was kept dry for 10 days, and the other in salt water for 87 days. Neither of them stood any measurable strain. Mr. Macgregor also noted that the samples contracted very much in setting, which indicates too much carbonate of lime. The irregularity in composition of the Moeraki boulders is so great that it would be practically impossible to manufacture cement from them of a uniform quality; one kiln might be equal to the best Portland, and the next quite worthless. We may therefore conclude that the expense of selection on the one hand, and the risk of failure on the other, are insurmountable obstacles in the way of its general utilization.

Artificial Cements.

When I began to investigate the subject of native cements and limes, I was under the impression that we had no stone capable of furnishing hydraulic limes, consequently some little time was devoted to the consideration of providing an artificial substitute; but the existence of natural cementing ingredients of a high character having been fully established, the necessity for adopting the latter expedient is removed, the subject will therefore be dismissed in a few words.

As you are probably aware, English Portland cement is made from two of the most common and abundant raw materials in the country—chalk and clay—and the manufacture is equally simple. The materials are mixed in the proportion of seven of the former to three of the latter, then burned in a kiln and pulverized as already described. In Germany, where there is no chalk, a substitute is found in hard limestone. This entails extra labour in pulverizing the raw material as well as the cement, but the result is practically the same.

Ordinary yellow clay does not make good cement; that in common use

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is a dark blue unctuous variety found in tidal estuaries and swamps. Blue clays, supposed to be suitable for the purpose, are abundant throughout the province. A sample from the railway cutting at Caversham was analyzed by Professor Black with the following results, which are shown alongside an English type:—

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Otago Clay. English Clay.
Silica 65.28 68.45
Alumina 23.18 11.64
Iron 3.20 14.80
Lime and magnesia 2.58 0.75
Alkalies 1.04 4.00
Water 5.19
100.47 99.64

These figures are not near enough to prove that this clay is good for making cement, but they are sufficient to show that there is every chance of getting the proper kind if required.

Portland cement is a low-priced article, the value of which is more than doubled by the charges of importation, and it can be manufactured without much skilled labour, consequently it is an industry that might well be started in New Zealand if there were no hydraulic limes to compete with it. The best places in Otago for a factory are the Waihemo and Aparima districts, both of which furnish soft limestones and fuel, the main requisites. The soft marl found at Waikouaiti and Greytown, being supposed to contain the ingredients of raw cement, was analyzed and gave the following result:—

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Clay 27.84 per cent.
Iron 11.24 "
Lime 24.78 "
Sand 35.16 "
99.02

The last item neutralizes the good qualities of the others, so we pass it into the category of unsuitable materials.

The idea of utilising the rich limes induced me three years ago to make an examination of volcanic clays to ascertain if they contained any of the properties of the Pozzuolanas of the old world that have been used from time immemorial to mix with lime in hydraulic works. About 40 specimens of all shades of colour imaginable were collected and tested by being made into mortar with an equal proportion of lime, then kept in water for two months. Four or five samples of drab and neutral tints gave indications of being feebly hydraulic, so possibly a more complete investigation would lead to the discovery of a material of considerable utility. The great objec-

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tion to Pozzuolanas is that, like the Moeraki boulders, uniformity of composition cannot be ensured.

Aggregates.

Except in the case of the higher hydraulic limes and cements, where the maximum strength is obtained by using them in a pure state, as much depends on the aggregate as on the cementing material, notwithstanding which there is no article used in construction that commands so little attention. The main essentials of a good aggregate are sharpness and freedom from earth or other impurities of a similar nature. The proper size and hardness vary with the quality of the cementing material;—rich lime takes a coarse soft sand, and cement a fine hard one.

As no attempt had been made to determine the relative merits of the Otago sands, I collected a number in the vicinity of Dunedin and experimented on them in the following manner, and with the results given in Table V. Each kind of sand was made into mortar with Waihola lime in the proportion of one of lime to two of sand. The lime had been air-slaked, and was sifted through a gold-dust sieve before being used. The ingredients were measured in the most exact manner, and carefully mixed with the smallest quantity of water that would give plasticity. The mortar was then used to cement ordinary bricks placed crosswise, which gave a bearing surface of about 18 square inches. After being kept in the open air for 160 days the bricks were pulled asunder with weights increased gradually to the breaking point. It will be seen from the table that the highest results were obtained from Anderson Bay sand, which broke with a strain of 226 pounds. About 1 ½ square inches of the mortar in the inside was not quite hard. Assuming that this only supported half as much as the other portion, we make the cohesive strength 13 pounds on the square inch. Two samples of each kind of sand were tested. Taking only the highest in each pair, we find that, out of a total of 27, four broke with strains ranging from 226 to 150 pounds, nine from 150 to 100, six from 100 to 75, and six from 75 to 47, while two did not stand any measurable strain. I regret to add that many of the last three classes are constantly used in Dunedin.

General.

In conclusion, I shall briefly recapitulate the leading points of my subject, and consider its practical bearing.

Leaving out the materials in Tables II. and IV., which are comparatively valueless, the following will show the various purposes for which the Otago limes are suited, each class being capable of performing the functions of those under it as well as its own:—

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Rich Limes.—
Nos. 9 to 14. Whitewashing and agricultural and caustic purposes only.
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"15 to 18. Brickwork in partitions and plastering.
"19 to 28. Low thin brick walls in a dry situation.

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Hydraulic Limes.—
  Nos. 11 to 13. Ordinary walling above ground.
  " 14 to 16. Foundations of ordinary buildings, concrete, and
engineering structures above ground.
  " 17 to 20. Nearly all the higher class masonry for which
cement is usually employed.

The rich limes are well dispersed throughout the province, but the hydraulic ones are confined to the vicinity of Dunedin, except we include the Lake Wakatipu deposits, the hydraulicity of which has not been proved. Although lime has been burnt on the Peninsula for many years, none of the good seams have been utilised. The proprietors inform me that there is no market for this quality. Builders will not use it in preference to the rich lime, as the latter carries more sand, and in the absence of any information on the subject, professional men and the public generally have no choice. In order to institute a comparison between the various articles under discussion, I have prepared the following statement, showing the strength and cost of mortars now used in Dunedin, together with an estimate of other kinds prepared from the hydraulic limestones.

Mortar.

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Tensile strength per square inch in pounds. Cost of mortar for a cubic yard of brickwork.
Now in use s. d.
  Portland cement with 2 of sand 205 14 6
  " " " 3 " 140 11 0
  " " " 4 " 100 9 0
  " " " 5 " 50 8 0
Rich Lime “2 ½ 15 3 9
Estimates for new mortars—
  Weak hydraulic lime slaked 50 4 0
Ordinary " " ground in mixing 100 4 6
Strong " " shell lime ground 140 7 0

In contrast to the above it should be stated that ordinary hydraulic mortar in England costs from 1s. 10d. to 2s. per cubic yard.

Judging by the quality of the ingredients, and the manner in which they are manufactured, I should not estimate the tensile strength of our ordinary lime mortars at more than ten pounds per square inch, which is less than half the strength of European mortars that are designated “bad” Their defects are quite apparent to any one who takes the trouble to examine the southern side of a building. It will be found that, after a lapse of years, the mortar even on the surface is often quite soft and friable. A good

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example which I noticed lately exists in the masonry of the Waitaki Bridge, erected in 1869; although apparently well proportioned and prepared, the mortar in some places is still no harder than stiff clay. There is no greater anomaly in the constructive arts than what is displayed in the use of weak mortar with strong bricks. We might as well connect plate iron with lead rivets. In designing a bridge or a roof every part is strained alike, so there is nothing wasted; but in the case before us, three-fourths of the work is thirty times stronger than the remainder. As shown above, the cost of increasing the strength of our mortars five times is 3d., and ten times 9d. per cubic yard of brickwork. These figures would only represent £10 and £30 on the new telegraph office, so the question of expense cannot stand in the way of the substitution of hydraulic limes for those in common use.

At present the annual consumption of Portland cement in New Zealand is about 40,000 casks, representing an expenditure to the consumer of £40,000. Of this quantity I am confident that nine-tenths is used in works for which our native products are equally well adapted; indeed, with the exception of some wet tunnel lining and foundations, where quick setting was a desideratum, there have been few works executed in New Zealand that required cement. We are, therefore, spending £36,000 on a foreign article, while a native one that would serve our purpose can be obtained at half the cost. This state of affairs has resulted entirely from ignorance of our resources, and of the quality of the materials within our reach.

The principal hydraulic limestones of the Peninsula are rather inaccessibly situated; at present their only outlet is by road to Dunedin, a distance of ten miles, but a moderate expenditure on a tramway two miles long would connect them with the proposed Portobello Railway and the waters of the harbour. The deposit at Dowling Bay occupies a very favourable position on the beach, four miles below Port Chalmers. The new road to the Heads passes through it, and there is deep water within a few yards of the limestone rock.

In order to utilise these stores of hydraulic limes to the best advantage, I would suggest the adoption of a plan that seems to have been followed in America: The quality of the stone, not only in each quarry, but in each bed of that quarry, is so clearly determined that its name conveys a distinct meaning to professional men who stipulate for certain kinds in certain work. Gradually the names acquire a commercial value, like the brands in ordinary manufactures, and thus the public generally acquire the knowledge necessary to ensure each article being used in its proper place.

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Table I
Analyses of otago limestones that furnish rich limes, with english and foreign types.
Number Description Locality. Lime and Carbonate of Lime. Carbonate of Magnesia. Silica Soluble. Silica. Insoluble. Alumina Soluble. Alumina. Insoluble Sand Insoluble. Clay partly-Soluble. Sesqui-oxide Of Iron Insoluble. Oxide of Iron Soluble. Carbonate of Iron Soluble. Iron Alumina. Insoluble Matter not Determined. Alkalies Water and Loss. Analyst or Authority. Remarks.
English & Foreign Types
1 Statuary marble Italy 100.00 M. Vicat
2 Ordinary chalk England 99.50 0.50 Various
3 Strasbourg stone France 98.00 2.00 M. Berthier
4 Yellow vesicular " 97.00 2.00 0.60 0.40 M. Vicat
5 Portland Oolite Dorset, Eng. 95.16 1.20 1.20 0.50 1.94 Profs. Daniel and Wheatstone In common use as building stones
6 Ordinary limestone Barnack, " 93.40 3.80 1.30 1.50
7 Ketton Oolite Rutland " 92.17 4.10 2.83
8 Carboniferous Whiteford " 89.75 0.60 8.88 0.85 Dr. Clarke
Otago Limestones
9 White crystalline Southland 98.80 Trace Trace 1.20 1.20 Dr. Hector Jurors' Reports, N.Z. Exhibition
10 Faint yellow do Winton 97.90 " " 0.60 Trace " " " " " "
11 Yellow fossiliferous Kakanui 97.00 1.00 1.50 0.50 Dr. Black Laboratory Report, 1875–6
12 Do do Oamaru 95.95 2.17 0.60 0.45 Trace 0.74 Dr. Hector Jurors' Reports, N.Z. Exhibition
13 White granular Waihola 95.76 Trace 3.32 0.92 " "
14 Yellow lithographic Oamaru 95.18 1.29 not estimated 1.20 0.47 2.33 " " Trace of sulphate, Jurors' Reports, N.Z. Exhibition.
15 Grey and yellow travertine Dunstan 95.04 2.56 Trace 0.60 1.80 " " Jurors' Reports, N.Z. Exhibition
16 White compact Waihola 94.66 Trace 4.05 1.29 " " " " " "
17 Grey granular Oamaru 93.43 2.58 0.50 1.01 Trace 2.45 " " " "
oxide " "
18 Bluish grey, top seam Dowling Bay 92.91 1.96 0.31 2.82 1.09 1.41 0.34 0.43 1.27 Dr. Black " " " "
19 Fawn granular Aparima 92.20 Trace not estimated Trace 2.20 5.60 Dr. Hector " " " "
20 Grey compact Wakatipu 91.60 2.94 0.20 " 0.84 4.42 " " " " " "
21 Bluish do Horse Range 90.99 2.16 3.10 " 0.62 2.90 0.23 " " " " " "
22 Grey shelly Southland 90.80 Trace not estimated 2.29 not estimated 6.89 " " " " " "
23 White granular Oamaru 90.14 0.46 1.54 0.54 7.14 0.18 " " " " " "
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Table II
Analyses of Otago Limestones that furnish Poor Limes, with English and Foreign Types.
Number Description. Locality. Lime and Carbonate of Lime. Carbonate of Magnesia. Silica Soluble. Silica. Insoluble. Alumina Soluble. Alumina. Insoluble. Sand Insoluble. Clay partly Soluble. Sesqui-oxide of Iron Insoluble. Oxide of Iron Soluble. Carbonate of Iron Soluble. Iron Alumina. Insoluble Matter not Determined. Alkalies Water and Loss. Analyst or Authority. Remarks.
English & Foreign Types
1 Sandy stone of Calraic France 70.00 2.00 1.25 24.75 M. Vicat
2 Coarse stone of Dessin " 61.89 7.44 3.10 1.57 26.00 " "
Otago Limestones.
3 Grey Caversham 68.51 Trace 0.72 1.79 0.79 27.65 0.54 Dr. Hector Jurors' Reports, N.Z. Exhibition
4 Greyish yellow Kaikorai 68.50 27.60 2.40 0.80 0.42 " " " " " "
5 Dark grey Waikouaiti 65.77 Trace 2.83 31.40 " " " " " "
6 " " Upper Harbour West 64.60 1.16 1.00 3.00 Trace 30.01 0.22 " " " " " "
7 Grey Pleasant River 64.10 29.50 1.20 0.80 " " " " " "
8 Bluish grey " " 63.08 1.10 0.63 0.60 0.83 29.53 4.22 " " " " " "
9 Greyish yellow Kaikorai 62.80 28.00 5.50 1.80 0.60 " " " " " "
10 Light yellow Waihemo 61.60 0.28 1.80 1.20 34.80 0.32 " " " " " "
11 Dark Grey Kaikorai 60.86 1.99 1.57 2.90 1.78 30.19 0.71 " " " " " "
12 Moeraki boulder Moeraki 60.50 2.50 21.00 14.00 2.30 Dr. Black Laboratory Report 1875–6
13 Bluish grey Caversham 53.00 24.40 19.10 1.40 2.20 Dr. Hector Jurors' Reports, N.Z. Exhibition
14 Greenish grey " 51.22 1.56 2.92 43.64 2.66 " " " " " "
15 Bluish grey Hawksbury 51.17 25.00 21.50 0.80 1.90 " " " " " "
16 Compact dark blue Wakatipu 50.79 2.80 0.23 23.58 8.84 7.49 1.56 2.80 1.91 Dr. Black 12.46 per cent of silica in form of sand
17 Dark grey Hawksbury 50.05 1.70 0.70 2.94 0.90 42.94 0.77 Dr. Hector Juror's Reports N.Z. Exhibition
18 Fine grey, soft Waihola 43.30 Trace 27.60 19.00 2.40 0.70 Dr. Black 21.98 per cent, of silica in form of sand
19 Buff yellow Kaikorai 42.10 21.00 29.30 1.70 5.90 Dr. Hector Jurors' Reports N.Z. Exhibition
20 Dark grey Tokomairiro 41.20 Trace 5.20 52.20 1.40 " " " " " "
21 Pale yellow Kaikorai 40.45 1.70 3.40 1.75 Trace 46.80 5.90 " " " " " "
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Table III
Analyses of Otato Limestones that Furnish Hydraulic Limes with English and Foreign Types.
Number Description Locality. Lime and Carbonate of Lime. Carbonate of Magnesia. Silica Soluble. Silica Insoluble. Alumina Soluble. Alumina Insoluble. Sand Insoluble. Clay Partly Soluble. Sesqui-oxide of Iron Insoluble. Oxide of Iron Soluble. Carbonate of Iron Soluble. Iron Alumina. Insoluble Matter not Determined. Alkalies, Water, and Loss. Analyst or Authority. Remarks.
English & Foreign Types
1 Shelly stone of Nièvre France 88.00 6.85 4.00 1.15 M. Vicat Feebly hydraulic; sets under water in 15 days.
2 Aberthaw England 86.20 11.20 2.60 Hy. Reid
3 Bituminous bluish grey France 82.25 10.50 5.50 1.71 M. Vicat Sets under water in five days.
4 Theil Limestone " 81.36 1.00 14.90 1.70 1.10 Gen. Gilmore Used in Port Said breakwater
5 Blue Lias of Lyme Regis England 79.20 17.30 3.50 Hy. Reid Used at London Docks
6 High Falls Stone America 79.04 11.10 2.52 peroxide 1.42 4.54 Prof. Boynton
7 Yellow France 77.40 13.25 8.35 1.00 M. Vicat Eminently hydraulic; sets under water in three days.
8 Metz Limestone "" 77.30 3.00 15.20 manganese 1.50 3.00 C. Tomlinson Eminently hydraulic.
9 Lezoux "" 72.50 4.50 23.00 ""
10 Blue Lias of Holywell England 71.55 1.35 20.10 3.52 2.21 0.84 Dr. Muspratt 74.73 soluble in acids.
25.27 insoluble
Used in the Liverpool Docks.
Otago Limestones—
11 White conglomerate Oamaru 87.08 Trace. not estimated. 2.85 0.79 8.58 0.78 Dr. Hector Jurors'Reports, N.Z. Exhibition”
12 Dark compact Portobello 86.80 " " 0.80 Trace. 12.40 " " " "
13 Dark fawn compact Peninsula 86.05 2.22 0.20 7.00 0.90 3.57 0.55 0.97 1.46 Dr. Black 3.17 p. ct. silica in form of sand.
14 Drab granular, 5th low'st seam Dowling Bay 84.03 0.33 10.93 1.23 2.76 1.00 0.98 1.26 " " Trace of sand and mica.
15 Fawn compact Peninsula 82.03 Trace. 0.36 9.10 2.30 2.53 0.55 2.80 0.33 " " 2.67 p. ct. silica in form of sand.
16 Yellowsih do. Portobello 81.10 1.70 not estimated. Trace. 0.60 16.60 Dr. Hector
17 “Fawn, top seam Peninsula 77.97 1.98 0.22 10.51 1.61 4.21 0.85 1.53 1.12 Dr. Black 3.60 p. ct. silica in form of sand.
18 Drab granular, 2nd highest seam Dowling Bay 78.87 0.80 0.62 12.70 1.52 4.05 oxide 0.70 0.35 0.39 " 3.80 p. ct. " "
19 Dark faw, 3rd do. " " 69.70 1.50 0.31 18.87 0.80 3.74 0.69 1.30 2.09 " " 7.60 p. ct. " "
20 D. do., lowest seam Peninsula 69.46 2.26 0.16 18.69 2.10 3.16 0.95 2.34 0.97 " " 7.03 p. ct. of sand, but mixed with some clay.
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Table IV.
Analyses of Otago Cement Stones with English and Foreign Types.
Number Description Locality. Lime and Carbonate of Lime. Carbonate of Magnesia. Silica Soluble. Silica. Insoluble. Alumina Soluble. Alumina. Insoluble Sand Insoluble. Clay Partly-Soluble. Sesqui-oxide of Iron Insoluble. Oxide of Iron Soluble. Carbonate of Iron Soluble. Iron Alumina. Insoluble Matter not Determined Alkalies, Water, and Loss. Analyst or Authority. Remarks.
English&Foreign Types
1 Raw materials Portland cement England 69.87 20.54 3.49 4.44 1.66 Various
2 Portland cement, artificial "68.11 20.67 10.43 0.87 Manufactured by White Bros.
3 " " " " 62.00 23.00 8.00 4.00 Hy. Reid Average quality.
4 " " Germany 60.40 23.86 9.20 peroxide 5.12 1.92 Herr Feichtenge
5 Boulogne cement stone France 63.60 23.80 6.00 6.60 C. Tomlinson
6 Portl'nd cement, natural Boulogne 65.13 0.58 20.42 13.88 Various Quick setting.
7 Calderw'd cement stone Scotland 71.30 8.80 3.40 protoxide 10.20 6.30 Prof. Penny
8 Vassy " " France 63.80 1.50 14.00 5.70 11.60 3.40 C. Tomlinson Quick setting.
9 Rosendale " " America 63.76 27.70 2.34 peroxide 1.26 4.94 Gen. Gilmore " "
10 Yorkshire " " England 62.54 24.00 1.31 Various
11 Sheppy " " " 61.40 18.00 5.25 manganese 6.75 "
12 Harwich " " " 52.00 9.37 17.75 11.37 " 7.50 per ct. sulphae of soda, etc.
Otago Cement Stones
13 Septarian boulder Moeraki 72.40 0.30 0.80 17.80 8.70 0.60 Dr. Hector Colonial Museum Report, 1870–1.
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Table V.
Tensile Strength of Waihola Lime Mortars with Different Sands.
No. Description Locality. Weight in lbs. Required to Tear Asunder Bricks. Remarks.
1 Grey, with faint yellow tinge; fine, but sharp. Mr. Knox's pit, Anderson Bay. 226 1 ⅓ sq. inches in middle not quite hard.
218 2 " " " "
2 Grey; fine, and sharp; small quantity of clay. Railway cutting at English Church, Caversham. 212 Good bed, uniformly hard.
nil. Broke in fixing; flaw in bed.
3 White; very soft, clean, and fine. Railw'y cutting at Abbott's Creek. 150 Uniformly hard throughout.
136 " " "
4 Round quartz gravel. Mr. Cutten's pit, Anderson Bay. 158 Uniformly hard throughout.
109 " " but not all adhering.
5 Dark grey; irregular and soft. Mr. Casey's pit, Anderson Bay. 143 2½ sq. inches in middle not quite hard.
122 Thickish bed; soft in centre.
6 Yellowish grey; fine, very sharp. Mr. Knox's pit, Anderson Bay. 143 2 ½ sq. inches in middle not quite hard.
67 2 ½ " " " "
7 Quartz gravel. Railw'y cutting at Abbott's Creek. 140 Uniformly hard.
82 Not adhering properly.
8 Reddish yellow, irregular; clay and quartz. Railw'y cutting at Abbott's Creek. 138 Very thin good bed; uniformly hard.
88 Bed not good.
9 Deep red; coarse; irregular. Railw'y cutting at Abbott's Creek. 138 Uniformly hard.
nil. Broken on shelf.
10 Deep reddish yellow; fine and sharp. Mr. Cutten's pit, Anderson Bay. 122 Piece in middle like a small oyster not quite hard.
122
11 Orange; very soft and fine. Railw'y cutting at Abbott's Creek. 106 Not well set.
97 " " "
12 Whitish grey; soft. Mr. Casey's pit, Anderson Bay. 102 2 ½ sq. inches in middle not quite hard.
nil. Broken on shelf.
13 Yellowish grey; soft. Mr Casey's pit, Anderson Bay. 102 Not well bedded.
nil. Did not carry 28lbs.; seems to have been broken.
14 Greyish white; fine; very sharp. Mr. Knox's pit, Anderson Bay. 96 Uniformly hard.
nil. Broke in handling; not adhering properly to bricks.
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15 Reddish yellow; fine and sharp. Mr. Casey's pit, Anderson Bay. 88 2 ½ sq. inches in middle not quite hard.
nil. Did not lift 21 lbs.; not quite hard; not adhering well.
16 Grey; fine. Railway cutting at Cargill Hill 82 Good bed; uniformly soft.
68 " " " "
17 Grey and yellow; fine. Railway cutting at Cargill Hill. 82 Good bed; uniformly soft.
nil. Did not carry 28 lbs.
18 Greyish yellow; very sharp. Mr. Harris's pit, Anderson Bay. 81 Good, bed; 3 sq. inches not hard.
70 " " 5 " "
19 Yellowish grey. Railway cutting at English Church, Caversham. 75 Uniform consistency throughout.
nil. Broke in handling; not bedded.
20 Yellow; fine and sharp Mr. Harris's pit, Anderson Bay. 67 2 sq. inches not quite hard.
nil. Would not stand handling.
21 Deep reddish yellow; fine and sharp. Mr. Cutten's pit, Anderson Bay. 65 Bad bed; soft in. heart.
nil. Did not lift 28 lbs.; piece like a small oyster not quite hard.
22 Deep orange; very sharp Mr. Cutten's pit, Anderson Bay. 61 Very good bed; 4 sq. inches; not quite hard.
nil. Broke in handling.
23 Light orange; very sharp. Mr. Cutten's pit, Anderson Bay. 61 Good bed.
nil. Did not carry 28 lbs.
24 Yellow; sharp and fine. Railway cutting at Cargill Hill. 54 Good bed; soft throughout.
nil. Did not carry 14 lbs.; bad bed.
25 Yellow; sharp and fine. Railway cutting at Cargill Hill. 47 Pretty well set.
nil. Broke with about 10 lbs.
26 Yellow; mixed with pebbles as large as peas. Railw'y cutting at Abbott's Creek. nil. Broke in handling.
nil. Did not carry its own weight soft throughout.
27 Yellow; fine and sharp. Railw'y cutting at Abbott's Creek. nil. Broke with its own weight.
nil. Do do; had not set.