DoBSON. — Notes on the Glacial Period. 295 



such as the wearing down of the mountains by glacial and other action, and 

 the destruction of laud by the sea — have all tended to render the climate less 

 rigorous, the subsidence of the land has to be looked to as the chief cause of 

 the termination of what may be called, for the sake of convenience, the glacial 

 period. 



On the west coast of the Middle Island the effects of glacial action, as 

 exhibited by masses of moraine matter covering large areas, are so striking as 

 to arrest the attention of even the most superficial observer. Struck by the 

 recent appearance of many of the moraines, and the manner in which glacial 

 drift caps the general drift of the country, I have ventured to collect the 

 numerous notes I have made during the last ten years, and from them deduce 

 what I conceive to have been the changes which have taken place duxing the 

 latest geological periods. 



At the end of the pliocene period I consider that but little of the 

 Middle Island stood above water; the main back-bone of the island probably 

 constituted a series of rocky islands, the sea level being about 2,000 feet 

 higher during this period, which must have been of great duration; the 

 gravel drifts were formed which cover the greater portion of the level lands, 

 and cap all the older formations from Nelson to Hokitika. During this period 

 were formed the Moutere Hills, and all that great face of drift hills which 

 occupies the whole of the depression between the east and west ranges, froui 

 the southern shores of Blind Bay to Lake Rotoiti. Here the drift formation is 

 interrupted by the mountains which divide the Lakes Rotoiti and Botoroa, 

 and also by the mountains forming the watershed between Botoroa and the 

 westward streams. Again, the drift formation occurs in the valleys of the 

 Matakitaki and Maruia, and then continues on almost uninterruptedly, capping 

 the older rocks throughout the flat country right down to the Mikonui Biver. 

 Following the coast northwards from the Grey, the drift again occurs in all 

 available places for deposition at heights varying from 10 to 500 feet above the 

 present se'a level. The reason for the drift attaining such a much greater 

 height at the head waters of the Buller and Grey was, that there the drift was 

 free from the destructive effects of stormy seas, and was deposited by streams 

 flowing into a quiet strait protected by high land on the east and west, and was 

 subjected only to the settling action of marine currents running through the 

 strait ; whereas on the coast line the heavy westerly swell from the Pacific, 

 aided by the strong littoral currents, prevented the deposition of drift except 

 in sheltered places. 



It was during this period that the formation of the great gravel drift 

 of the Canterbury plains began. The country there began to rise, and 

 although the foruiation of gravel drifts continued on the lower levels, the 

 waters of ijrecipitatioJi began to carve them on ihu higher levels into the forms 



