itself, in reality, is a portion of the more inland, plain-area that has been filled in by the material brought down by rivers such as the present Tuki tuki, Maraetotara, Ngaruroro, Tutaekuri, and Esk, all of which now flow from the westward, some as far back as the Ruahine Mountains and the Kaweka. The plain known as the Heretaunga Plain is a late formation; in fact, the process of growth is still going on, and the action of floods on the waters of the bay is such as to bring about a slow sedimentation of the area that was at one time a land-area connected in structure and formation with the hills forming Scinde Island, Napier, and the rocks exposed along the northern and southern ends of the bay. What is here said of the growth and changes connected with Hawke's Bay can also be said of the plain-area

Fig. 2.—East Coast after Subsidence; New River-Basins.

between the mouth of the Wairoa River and Te Kapu or Frasertown, some ten miles inland. So, too, the Poverty Bay plain forms a part of the water-area, and both of them occupy the place once occupied by hills that united Young Nick's Head with the hills that now bound the coast along what is known as the Kaiti side of Poverty Bay.

The east coast between East Cape and Cape Turnagain at one time extended much farther seaward. The map marked fig. 1 shows some of

the extension. At the time when this condition existed the general slope and river system of the Island were very different from what is now the case. The slope was generally to the east by south, and the Ruahine, Kaweka, and Titiokura Ranges had not then reached their present elevation. The volcanic district was directly associated in slope and drainage with the-east side, and numerous tributary streams carried their burdens of shingle, pumice, and vegetable material from the back inland country, and spread them broadcast over basin-like areas in a river-valley of great length that was in process of making by the slow elevation of what now constitutes the chief axial structure of the Island.

Fig. 3.—East Coast, Showing Plain-Growth Since Subsidence. Shading Shows Plain-Growth—the Plains filled and formed since Subsidence Shown on Fig. 2.

In order to obtain a clear idea as to the surface features of the country at the time under notice, map fig. 1 should be studied. It shows the probable extension of the coast eastward beyond what can be seen in the dotted lines of the present coast, and the various streams that now constitute different river systems are seen to form one river that had its head-waters in the back country to the westward of Poverty Bay. Out in the ocean to the south-east of Poverty Bay the river made a bend to the south by west, and proceeded past the Mahia, through Hawke Bay, and south-west into the valley now known as the Heretaunga Plain, and thence west by south onward to the Wairarapa. On its course it received from the back

country a large number of tributary streams, most of them being heavy shingle and pumice carriers. By means of the network of tributaries from the west, the country was bared of a large part of the limestone that covered it at the close of the Pliocene period, being replaced by heavy deposits of shingle and pumice of great thickness, and of a kind that is now characteristic of the country between the Kaimanawa Mountains and Tauranga-Taupo.

Towards the close of the Pliocene and the opening of the Pleistocene periods great and important changes took place. Great volcanic activity was experienced in the interior of this Island, and the east coast was shaken to its foundations. It was during this period of activity that a large portion

Fig. 4.—East Coast, Showing River Systems As At Present.

of the coast disappeared and sank beneath the ocean. Hawke Bay, Here-taunga Gulf, Wairoa Gulf, Poverty Bay, and Turanganui Gulf were formed at this time.

The Great Wairarapa disappeared as a river, and the entire aspect of the water drainage was modified. A reference to map fig. 2 shows the condition of the coast and the physical features of the land following the subsidence and the disappearance of the Great Wairarapa river-basin.

What had formerly been tributaries of a great river now began to form separate basins of their own, and we have the interesting fact that by ordinary earth-movements new rivers and river systems may be brought into existence and the facies of a country completely changed.

An inspection of the areas that now form the river-basins shown in map fig. 2 will supply the fullest evidence of a contemporaneous past in the shingle, pumice, sand, and vegetable deposits that are found within them. In Poverty Bay, the Kaiti Hills, the lower hills on the Whataupoko, the hills near Ormond, Te Karaka, and numerous others abound with facts to show the state of the country before the present plain and river-valley were in existence. Similar evidence is forthcoming in the case of the Wairoa, Mohaka, and the other river-basins of Hawke Bay. At the entrance to the Wairoa and Mohaka Rivers, and on the hills towards Frasertown and the Wairoa Hospital, shingle and pumiceous deposits occur, and in the inner portion of Cape Kidnappers, extending from the Black Reef, sections 200 ft. in vertical height display the same characteristic beds such as are met with,

Fig. 5.—Turanganui Gulf, After Subsidence.

though less developed, in Poverty Bay. To the north-west and south-west of the Kidnappers, through Maraekakaho, and thence past the Gwavas Station on to the Ruataniwha Plains, the hills both to the right and left are made up solely of the Kidnapper and Poverty Bay shingle series, and these continue through Takapau, Ormondville, Matamau, and Dannevirke in varying thickness and extent.

All the deposits within the limits of the areas named bear witness to the fact that the supply of materials was from the westward. There was

a general similarity in the physical conditions of the whole district at the time, and the flora and fauna were much like those of to-day. Over the whole area there are usually traces of lignite-beds of varying thickness. These occur along with what appears a pumice-mud deposit. In these beds fossil specimens of leaves occur of many kinds. I have collected more than a hundred kinds in a state of perfect preservation. In the same beds are specimens of fossil fish vertebrates, insects, flowers, and ferns, and a single specimen of a fossil feather.

The beds have not been by any means carefully explored, and a rare garnering awaits the young geologist who is anxious to make a collection representing the animal and vegetable life of an interesting period in the geological history of this country. Kidnappers, Whataupoko, and Ormond are the best collecting-grounds at the present time.

An inspection of map fig. 2 will show that the rivers which were suddenly brought into independent being had to carve out a destiny for themselves. The country was high, and covered with deposits of shingle, limestone, and in some places blue-clay marls. Each river-mouth was miles from where it is now to be found. Denudation was great, and loose material was easily removed seaward, and deposited in the small gulfs and

Fig. 6.—Cross-Section Showing Filling-In Of Beds.

bays along the coast. The Tukituki had to carve out a way for itself, but this took a long while to accomplish, for, with the Makaretu and Waipawa Rivers as helpers, a place had to be worn through the limestones at the spots known as the Waipawa Gorge and the Waipukurau Gorge respectively. Lakelets were formed, to be broken through from time to time as the river kept finding its course to the sea. The Ngaruroro and Tukaekuri Rivers began to pour their waters into the area now occupied by the important Heretaunga Plain, which grew at a rapid rate, as soon as the Tukituki began to pour its burden of shingle into the bay in the vicinity of the gorge behind Havelock.

Map fig. 3 shows the work that has been done by the several rivers since they came into existence, following the great subsidence along the coast. Ruataniwha, Heretaunga, Wairoa, and Poverty Bay Plains have all been formed by means of the materials that the several rivers have carried down in time of flood. Slowly the mouths of the rivers have extended

seawards as the deltoid areas have grown year by year, and rich lands have taken the place of the once water-area, and the same process of growth is going on to-day. The rivers are still carrying down their treasures of material to the lowlands, and these latter are being aided by man's intelligence and industry. Since the formation of new drainage-areas and river

Fig. 7—Artesian-Well Section, Showing Details Of Bedding.

systems, as shown in map fig. 2, the “made land” along the coast, as won from the sea, must amount to over 150,000 acres, and carries a population of about forty thousand persons. It would be interesting to know the annual value of the products of the land that has been made by deposition from flooded rivers, but the facts are not available.

Map fig. 4 shows the east coast as it is to-day, with the several rivers running into Poverty Bay and Hawke Bay respectively. The plains are not to be distinguished from the other portions of the land-area, for nature heals wounds, and only leaves remnants of a past, after the manner of a camping-ground in the case of Natives or a party of picknickers.

In a former paper on “Artesian-water Basins of Heretaunga Plain” (Trans. N.Z. Inst., vol. xxxvii, p. 432), sections are shown to illustrate the growth of the plain, and reference is made to the Great Wairarapa that flowed over the area long before the plain was formed. At that time my inquiries had not extended to Poverty Bay, but the sections (figs. 5, 6, 7, and 8) give in regular sequence the geological events and proofs such as are given in the above paper with respect to the Heretaunga Plain.

Fig. 8.—Present Plain-Slope And Physical Features.

At the time of subsidence a gulf extended inland of the present Poverty Bay even beyond Kaiteratahi, and into this gulf, which is named Tauranganui, several important rivers flowed. As in the case of Heretaunga Plain, the rivers were and are great carriers of débris, and the plain as a deltoid changing area has grown in a manner almost identical to that of Heretaunga, so that the work of growing is still in progress.

The cross-section (fig. 6) shows the bedding of the present plain from the hills near the school at Te Arai, and the hills over which the road passes to the Waimata. Along the plain is shown the location and depth of artesian wells that have been put down from time to time, and fig. 7 shows a complete section of one such well. The present slope of the Poverty Bay Plain is shown in fig. 8, which gives heights, and river-drainage, and railway-line.