340 Transactions. 



begins to shallow. The only summit mentioned in the report,* apart froirt 

 the Hector Mountains, as showing ice erosion is Mount Nicholas, 4,827 ft. 

 high. I have personally seen no effect of ice erosion due to a moving ice- 

 stream at a greater height than 4,000 ft. on Mount Dick or 5,000 ft. on 

 Ben Lomond. 



There is here evidently a difference of opinion as to facts ; yet the 

 aspect of the Tooth Peaks, near the Greenstone ; of the Bayonet Peaks, 

 5^213 ft., at Halfway Bay ; of the Cecil Peak, 6,477 ft. ; of the Walter 

 Peak, 5,946 ft., is in every case sufficient to prove to a geologist that none 

 of these peaks have been covered by ice. 



If we proceed still further into the hinterland there is everywhere the 

 distinct difference between the glaciated topography of the lower heights 

 and that of the unglaciated topography above, as is most clearly seen in 

 the Routeburn, the head of which is situated on the main watershed, where 

 the ice must have had its greatest thickness. The statements that have 

 been made show that a maximum thickness of 5,240 ft. of ice is all that 

 can be allowed for the great Wakatipu Glacier. Even this thickness will 

 probably appear surprising at first, and may even seem to justify the state- 

 ment that an ice-sheet overspread the lowlands. It is therefore as well to 

 compare this with the probable thickness of the ice of our present existing 

 glaciers. 



In the first place it must be recognised that when an ice-sheet descends 

 to a low level or has a great thickness there is no reason to conclude that 

 all the country, or even adjacent valleys, are similarly affected. 



The Tasman Glacier has its terminal face at present 2,358 ft. above 

 sea-level, and the terminal face of the Franz Josef Glacier is 697 ft. above 

 sea-level. Yet there are in each case neighbouring valleys either without 

 ice or with only small glaciers at their heads. On the western side the 

 Douglas River rises to over 4,500 ft. before it disappears beneath the ice of 

 the Marchant Glacier ; on the east side the Murchison rises to 3,308 ft. 

 and the Cass to 5,209 ft. before the glacier is reached ; while further south, 

 on both sides of the main range, there are scores of valleys rising with gently 

 sloping floors to 3,500 ft., and yet they are innocent of glaciers. 



The mere mention of these facts shows that it is obvious that the height 

 of the valley-floor above sea-level does not settle the question as to whether 

 the valley will be occupied by a glacier. It is also obvious that the exist- 

 ence of long glaciers in some valleys does imply that other neighbouring 

 valleys will be filled with ice. It is an undoubted fact that the size of the 

 neve, the slope of the valley-floor, the amount of snowfall, are all characters 

 that have great importance in relation to the size of glaciers. 



It is seldom realised that the ice in our present glaciers is of great 

 thickness. Actual estimates based on measurements in New Zealand are 

 not at present available. It is, however, probable that we shall not err 

 gravely if we adapt measurements that have been made in Switzerland to 

 the slightly different dimensions of our own glaciers. Of all the Swiss 

 glaciers the Aar appears to be most similar to the Tasman ; but its length 

 is only ten miles, while that of the Tasman is 17-5 miles. The thickness of 

 the ice in the Aar Glacier is 1,312 ft. (400 metres : De Lapparent). If the 

 thickness of the Tasman has the same ratio to its length as that of the Aar, 

 it must be 2,296 ft. 



* Bulletin No. 7, N.Z. Geological Survey (New Series) p. 31. 



