Glacier Work. — Scott. 245 
distinction exists between these two classes, depending- upon 
the character of the material which is dropped, or extruded 
at the end of the glacier. The terminal moraine is composed 
of sharply angular blocks and fragments in the case of Alpine 
glaciers, as would be expected from the fact that the broken, 
angular mountain material has been carried --hiefly upon the 
surface or the upper and median portions of the ice. The 
ground moraine on the other hand which is so largely exem- 
plified in the Scandinavian and Greenland £^laciers, consists 
of sub-angular and striated stones and water worn gravel, 
showing the detritus is infra and flluvio-glacial material. 
Nansen and Chamberlin agree concerning the Greenland 
glaciers, that where no Nunataks occurred, no superficial 
detritus was visible; Chamberlin, as well as Salisbury, how- 
ever, both evidence the fact that the lower strata of the ice is 
crowded with ground moraine, and turbid water escapes in 
great volume from the "inland ice." The question naturally 
presents itself, where does all this detritus come from? It is 
evident that it cannot come from the sides of mountains, as is 
the case in Alpine glaciers, but must come largely from the 
land beneath the glacier. It has been shown by observation 
(Prof. Heim) that a glacier is capable of fracturing and 
sundering projecting masses of schist over which it flows, and 
it follows by observation of ground moraine material, that the 
glacier itself not only abrades and smooths but also ruptures the 
rocks over which it moves ; when the angle of slope and weight 
of the ice are sufficiently great, this is readily conceivable. 
Continental Glaciers. 
It is necessary to again refer to Agassiz, as the pioneer of 
■glaciology, for the original conclusion that the northern por- 
tions of both continents have been covered with immense ice 
sheets. His efiforts to prove the correctness of this opinion 
have been a great stimulus to others, who, since his time, have 
confirmed his views, and have shown that the ice sheet at the 
climax of the glacial period probably occupied an area af some 
2,500,000 square miles. This mass of ice had a depth of from 
1,350 feet on the northern slope of the mountains of Germany 
and 2,500 to 3,000 feet in Scotland, to 5,500 feet, even, in 
some of the Norwegia n fjords. * In North America a 
♦James Gelkle, 'Earth Sculpture,' pp. 232-233 
