and the evidence of their having existed in Britain. 571 



not have been accumulated by true glaciers, although the materials 

 may have often been derived from them ; and unstratified masses, 

 composed of blocks, pebbles, and clay. These stratified deposits 

 he considers to be of posterior origin to the glacier epoch. The till 

 of Scotland, or the great unstratified accumulation of mud and 

 gravel, containing blocks of ditferent size heaped together without 

 order, and containing no organic remains but bones of Mammalia 

 and insignificant fragments of shells, he is of opinion was also not 

 produced by true glaciers, although intimately connected with the 

 phaenomena of ice. The polished and striated surfaces of the blocks 

 leave no doubt on M, Agassiz's mind that these masses have been 

 acted upon by ice in the same manner as the blocks which are ob- 

 served under existing glaciers, and which are more or less re- 

 arranged by water derived from the melting of the glaciers. 



Similar detritus fills the bottom of all the Alpine valleys, as that 

 of the Rhone from its mouth to its junction with the Lake of Geneva, 

 and the valley of Chamounix : it is found between the Hospice de 

 Grimsel and the borders of the lower glacier of the Aar ; thence to 

 the neighbourhood of Goutharen in the valley of Oberhasli, at Im 

 Grund, in the plains of Meiringen, and in Interlasken ; also between 

 Thun and Berne. At all these localities, M. Agassiz considers, the 

 blocks were left, when the glaciers extended to them. 



With respect to the valley of the Aar, M. Agassiz says it is easy 

 to pi-ove that the rounded pebbles of Alpine rocks spread along its 

 whole course, were not transported to their present position by that 

 river, because between the glacier from which it issues and Berne, 

 the flowing of the stream is interrupted by the barrier of Kirchet, 

 the Lake of Brienz, and the Lake of Thun ; and because between 

 these lakes its velocity is so small, that it transports only mud and 

 very fine gravel, and that the pebbles over which the river flows 

 below Thun do not issue from the lake. Supposing that the vo- 

 lume of the Aar was formerly greater, why, asks M. Agassiz, are 

 not the lakes of Brienz and Thun filled in the same manner as the 

 plain of Meiringen and the bottom of the valley which separates the 

 two lakes ? All difficulties, however, he is of opinion, vanish, if 

 the pebbles be considered the detritus of retreating glaciers, and 

 that the hollows occupied by the lakes of Brienz and Thun were 

 filled with glaciers. 



The existence of a glacier in this valley is not imagined by the 

 author to explain the origin of the detritus, as its having existed is 

 proved by the polish on the rocks in situ, from the glacier of the Aar 

 to Meiringen, a distance of twenty English miles, at the height of 

 8000, 7000, and 6000 feet successively above the level of the sea ; 

 and even on the shores of the Lake of Thun. Similar pha^nomena 

 have been noticed by AL Agassiz in Scotland, in the valleys of 

 Loch Awe and Loch Leven, near Ballachalish, and in England in the 

 neighbourhood of Kendal. 



The author then proceeds to describe the moraines of Switzerland, 

 or the accumulations of blocks and pebbles deposited longitudinally 

 on the borders, and transversely in front, of glaciers, and success- 



