280 Reports and Proceedings— 



outer case, the friction of the ice in motion, at the above pres- 

 sure, increased the production of water 2>\ times above the 

 rate observed when the ice was still and exposed to a tem- 

 perature of 54° P. The amount of heat evolved was nearly 

 as much as with oak moving upon oak well lubricated, and the 

 coefficient of friction was between 04 and - 2. Glacier motion is 

 impossible without a continual supply of water to lubricate the 

 bottom. No doubt the action of denudation by glaciers produces 

 heat to a small extent. The water obtained by melting the surface 

 of the glacier by the sun's heat in the glacial period could not be 

 sufficient alone. The position of deep lakes in all parts of the 

 world in immediate connexion, with mountains and their absence in 

 places away from mountains shows that deep lakes are integral parts 

 of mountains ; and, in fact, lakes are deepest exactly where the 

 glaciers, once covering the mountains, were in the best position to 

 act as lake excavators. There can be no doubt that all deep lakes 

 in the world, including those in Central Africa, below the Equator, 

 are purely of glacial origin, and that the cold in the Glacial Period 

 was nearly equally intense in the southern and northern hemi- 

 spheres, and the Atlantic was not only lower, but great part of it 

 was frozen. Glacial surface-ice would move much faster than the 

 bottom-ice, and the side-ice than the surface-ice, and therefore 

 fractures would be continually occurring through all parts. The 

 water produced by this great friction of ice upon ice would fall 

 through the fissures to the bottom. He had pointed out that a 

 glacier moved twice as fast when it was eight times as thick, 1 and 

 the influence of weight on motion must be considered a most im- 

 portant element. The present temperature of a thin glacier was 

 found by Agassiz, from observation, to be one-third of a degree below- 

 freezing ; but Mr. Tylor assumed that in such a lake-glacier as he 

 had drawn, and supposed to exist in the glacial period, the tempe- 

 rature might be assumed to be very much below freezing, the greater 

 cold arising from immense evaporation and other causes. He there- 

 fore concluded that the water produced by friction of ice upon ice 

 falling to the bottom of the lake-glacier through fissures would rapidly 

 freeze, and then expanding one-tenth, would impel the glacier (shod 

 or armed with blocks of stone and sand at the bottom) up a gradient 

 of 1 in 20, excavating the Swiss and other lakes 30 or 40 miles long, 

 and 1200 feet deep in this manner. Mr. Tylor calculated that with 

 half an inch per annum of mean excavation over the whole lake- 

 bottom, the lake of Zurich could be excavated in 15,000 years. Prof. 

 Eamsay had pointed out, from geological evidence, that such lakes 

 have been excavated by ice, but he did not indicate how this was 

 mechanically possible (see Quarterly Journal, 1862). 



Mr. Tylor referred again to his experiment when the pressure Was 

 only 2 lbs. on the inch. In a large glacier such as described by Dr. 

 Hooker in the Himalayan range, where the mean gradient of the 

 surface was 40° to 50° and the actual fall was 14,000 feet in five 

 or six miles, Dr. Hooker found gi*eat lakes attendant upon the 

 1 Following the same law as flowing water. — See Phil. Mag. Sept. 1874. 



