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

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

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