5

a—9

The Upper Ohinemuri or Waihi Plain, on the east, is bounded by low hills, and on the south side by a cluster of hills, the eastern part of which is cut through and drained by the Waiau Stream, falling into the upper part of the Tauranga Harbour. Among these bills the water-parting winds irregularly, but trends generally in a south-west direction to the commencement of another definite range, which, from the source of the Whaitawheta Eiver, east of Mount Te Aroha, trends south to the limits of the district examined. This southern range, which is for the most part composed of moderately fine-grained volcanic breccia, is deeply cut into by gullies, and very abrupt on its western side. Its crest at frequent intervals is crowned by sharp or castellated crags, and stands in wonderful contrast to the smooth outlines of the last mountain to the south and the high sloping plateau plain that lies beyond in the direction of Tauranga and Eotorua. A lesser range, mainly composed of rhyolitic rocks, follows the coast-line from Mercury Bay Heads to Waihi Beach. A portion of this, east of Waihi Township, is for a short distance the main water-divide. Between Cabbage Bay and Coromandel, hilly country, at places rising into mountains, stretches along the shore of the Hauraki Gulf, and generally is separate from the main range in that part. The same applies to the coast-line between Coromandel Harbour and Tapu Creek, and, with the exception of the foot-hills along the borders of the plain west of the mountains south of the Thames, the only feature of consequence is the range that from the KarangahakeTe Aroha Bange runs out to the north-west some four miles on to the plain, and near its junction with the Karangahake-Te Aroha Eange is crossed by the coach-road from Paeroa to Te Aroha. The main water-divide of Cape Colville Peninsula, from the foregoing, it will be seen, is not one continuous range, but in reality consists of five sub-parallel ranges, the first four of which have depressions between them that lie nearly in a north-north-east and west-south-west line, and, assuming the ranges to have the same general direction (which is barely true of the third and fourth, but is of the first and second), they can be imagined as at a former period having extended beyond their present limits to the south-west. Some such extension of high land is necessary to account for peculiarities of the geological structure of these mountains, it being evident that extensive lakes at one time existed, of which the retaining barriers have long since been removed. The lacustrine strata referred to are found usually at considerable elevations, and forming in part the crests of the higher ranges. This and other peculiarities that come to light in a study of the physical features of the district can only be explained by having regard to the geological history of the Peninsula from prior to the deposition of the coal-bearing series, or the commencement of the Cretaceous period, to the present time. Those who have made the geology of New Zealand a special study do in most part agree that, towards the close of the Jurassic and during the early part of the Cretaceous periods, the land over and outside what is now the New Zealand area was not only much more extensive than it now is, but was also in particular regions elevated and mountainous in character. Generally, however, it is thought that the direction of its principal mountain chains were as now — i.e., in a northeast and south-west direction —and this in spite of the fact that it has been pointed out that the main lines of elevation in the Pacific Ocean are in the contrary direction, or as near as may be in a north-west and south-east direction. Hochstetter says, " The three islands of New Zealand constitute only parts of one and the same system of mountains, which, running from south-west to north-east, forms a distinctly marked line of elevation in the Pacific Ocean. This longitudinal line is crossed by a second, almost at right angles, which is indicated by the direction of Foveaux and Cook Straits, but still more so by the direction of the long-stretched north-west peninsula of the North Island. This north-west peninsula corresponds to the line striking N. 52° W., and designated by Dana as the axis of greatest depression in the Pacific Ocean."* Geologically, the oldest rocks of the Auckland Provincial District are found along the eastern side of the long peninsula extending from south of Auckland City to North Cape, and which Hochstetter shows lies parallel to the line of greatest depression in the Pacific Ocean.| Dana, in " Corals and Coral Islands," shows that the submerged lands of the Pacific Ocean over the coralbearing region have a general trend in a north-west and south-east direction, which is likewise the direction of the greatest depression in that ocean. On the south-west side of the great depression in the Pacific there is evidence also of a north-west trend of lines of elevation, and of depressions parallel to these—to wit, the Auckland peninsula, and its extension to the south-east, and the depression of Cook and Foveaux Straits. It is not difficult to imagine that the land of which the Auckland peninsula is a remnant was at one time prolonged to the north-west as far as Norfolk Island, and to the south-east as far as Bounty Island, the Chatham Islands lying in the line of this south-east extension. The broad expanse of deepest Pacific having always been ocean (Dana), and the lines of structural elevation to the north-east and south-west of this having the same direction, these, whether appearing above the waters as lines of low coral islands to the northeast, or as higher yet depressed lands to the south-west, must be regarded as the oldest and most permanent features of the physical geography of this division of the earth's surface. On the other hand, we have in the mountain structure of New Zealand and the islands themselves an axial direction from north-east to south-west, or at right-angles to that of the Pacific depression and its bordering lands. Which of these two are the oldest need scarcely be made the subject of discussion. Geological investigation within New, Zealand has made it clear to me that the Alps of the South Island and the mountains of the main chain in the North Island appeared at a comparatively modern date, and that the north-west and south-east axis, as illustrated by the North Auckland Peninsula, is of far older date. As part of this, the Cape Colville Peninsula trends nearly north and south, and is raised towards the north and north-west, and gives clear evidence of depression along its eastern side and southern end, w 7 here it abuts upon the mainland. The

* "New Zealand," by Hochstetter (English edition), p. 36, f " New Zealand," by Hochstetter, p. 37.