GLACIAL ACTION IN AUSTRALASIA. 239' 



glaciers in Thompson Sound ; and near Deas Cove, as well as on 

 the south side at the entrance to the Narrows, in Milford Sound, 

 the rocks are rounded as if they had been smoothed by ice. But 

 this may be deceptive, and the rounded surface may be due to the 

 decomposition of a granitic rock. Certainly the islands in the 

 sounds are not now mammillated or ice-smoothed, and they show 

 no sign of lee and strike sides, which is, no doubt, due either to 

 the wet climate, or to the great length of time which has jjassed 

 since glaciers filled the valleys ; or perhaps to a combination of 

 both causes. In either case it is difficult to believe that ice grooves 

 would still remain on rocks which are not covered by clay. 



Conclusion. — It thus appears that at the time of their greatest 

 extension the ancient glaciers of New Zealand were larger and 

 descended lower the further they were south. The terminal 

 moraines in N.W. Nelson go to 2,700ft. above the present sea 

 level ; Lake Rotoiti, in S. Nelson, to 2,000ft.; Lake Sumner, 

 probably a glacier lake, is 1,700ft. above the sea. In S. Canter- 

 bury the terminal moraines are 1,000ft.. and in S. Otago only 600ft. 

 above the present sea level. In Westland and in the West Coast 

 Sounds the glaciers advanced to below the present sea level. The 

 glacier of Boulder River was four and that of Lake Kotoiti about 

 twelve miles in length ; the glacier at the head of the Waiau-ua or 

 Dillon, fourteen miles ; that of the Rakaia, fifty-five miles ; the 

 Wanaka glacier, sixty ; that of Wakatipu, eighty ; and that of 

 Te Auau, sixty-five miles in length. There is, therefore, a con- 

 siderable difference in relative proportion between the ancient 

 glaciers and their present representatives, as a glance at the map 

 (Plate I.) will show. At present they reach their maximum in 

 South Canterbury, and get smaller both to the north and to the 

 south ; while in ancient times their maximum was in Central Otago. 

 This difference niriy, perhaps, be due to the Otago mountains having 

 then been relatively higher than they are at present ; or it may 

 have been due to the great breadth of mountains, at present from 

 4,000ft. to 7,000ft in height, in central Otago, which Avere probably 

 covered with snow during the great Glacier Period. 



B.— BIOLOGICAL EVIDENCE. 



In Europe and North America the geological evidence of a 

 former ice-age is accompanied by the biological evidence of a 

 southerly migration of arctic shells, which subsequently became 

 extinct as the ice-age passed away. In New Zealand we find 

 nothing of this kind of evidence, for the mollusca of the Pliocene 

 and Pleistocene beds show no sign of a refrigeration in climate.* 

 Indeed several of our living shells, which are not now found in the 

 seas of the southern parts of New Zealand, occiir in Miocene beds ; 

 consequently it would seem probable that the climate of the 



* Trans. N.Z. Institute, vol. viii., p. 385. 



