342 Trani<actioiis. 



There is also no question that the main stream of ice flowed towards 

 Athol. In order that there should have been any flow in that direction, the 

 upper surface of the ice must have sloped towards Athol. The Tasman 

 Glacier has a slope, of 229 ft. per mile in its flattest part. The Greenland ice- 

 sheet has a surface slope of 220 ft. per mile for the first 3,281 ft. of rise on its 

 eastern side, and 93 ft. per mile for the next 3,281 ft., according to Nansen. 



If we take the slope of the Wakatipu ice at 100 ft. per mile above 

 Kingston, and 300 ft. per mile from there onwards, we are not likely to 

 err much. 



We will suppose the thickness to be 7,490 ft. at a distance of five miles 

 from Kingston, where the upward slope of the lake - floor begins. At 

 Kingston, five miles away, the thickness of the ice would be 1,265 ft. less 

 owing to the rise of the lake-floor, and an additional 500 ft. less owing to the 

 ■downward slope of the surface of the ice. That is, at Kingston the thickness 

 will be reduced by 1,765 ft., and will therefore be 5.725 ft. This reduction 

 in thickness must be due to melting, and it amounts to 388 ft. per mile. 

 There is no reason to suppose that the rate of melting would decrease below 

 Kingston, and, if it did not increase, the terminal face of the ice would be 

 5,725 -h 388, or fifteen miles away — that is, at Athol. Here the terminal 

 moraine is actually situated. This estimate is based on the supposition 

 that the reversed slope had then its present form. It is quite possible that 

 it owes its steepness to the deposition of morainic matter which took place 

 when the ice began slowly to retreat. If so, the reversed slope must be 

 supposed to extend from the floor of the lake opposite Mount Dick to the 

 Dome Pass, where the rock-surfac6 is 1,300 ft. above sea-level. The end of 

 the slope at Athol will then be 1,565 ft. above its commencement twentv 

 miles away. If an average slope of surface of 150 ft. per mile be adopted, 

 3,000 ft. of thickness is accounted for within this distance. The reduction 

 in thickness is therefore 1,565 ft. -I- 3,000 ft. at this point, which leaves 

 2,925 ft. ; and with a slope of 150 ft. per mile the terminal face would be 

 near Lumsden. At this place there is not a terminal moraine, nor is any 

 known between it and the sea-coast. With my estimate of 4,000 ft. of ice, 

 the terminal face woidd, under similar conditions of slope, be at Athol. 



The result of this inquiry is, at any rate, of such a nature as to prove 

 emphatically that, with such a great thickness of ice in a valley glacier of 

 enormous dimensions, all comparison with an ice-sheet is fallacious. 



The statement that the imaginarv ice-sheet of New Zealand was con- 

 nected with another ice-sheet that simultaneoiisly extended northwards 

 from South Victoria Land is not at present supported by any evidence. 

 At first sight it appears to be reasonable to assume that a glacial advance 

 in New Zealand must have been due to some cause that would have 

 affected lands in the south in a similar manner. This, however, is a 

 conclusion that we are not justified in adopting. If a comparison is 

 made with North America, we find that at the time that ice advanced to 

 H latitude of 37° 30' in the Mississippi Valley, where now a mild, temperate 

 <-limate is experienced, Alaska was largely free from ice except on or about 

 the mountains, though now it experiences a climate of great severity. To 

 take another instance, Europe during the period of maximum ice-advance 

 was in the west covered by an ice-sheet as far south as the Thames Valley 

 in England, and to the parallel of 50° north latitude in Poland. At the 

 same time, in northern Siberia, at Werchojansk, where the mean annual 

 temperature is now 1-4° Fahr., and the January temperature is — 54-4° Fahr., 

 the surface of the land was not covered with ice. 



