730 LOUIS AGASSIZ. 



west. Its greatest thickness, as an indepen- 

 dent glacier, is no doubt marked, not by the 

 boulders lying higher up, but by the large 

 moraine which shuts in the lake. The direct 

 connection of this moraine with the glacier 

 in its former extension is still further shown 

 by two other moraines, on lower levels and 

 less perfect, but having the same relation to 

 the present terminus of the ice. The lower of 

 these is only one hundred and fifty feet above 

 the actual level of the glacier. These three 

 moraines occur on the western slope of the 

 bay. The eastern slope is more broken, and 

 while the rounded knolls are quite as distinct 

 and characteristic, the erratics are more loosely 

 scattered over the surface. In mineralogical 

 character they agree with those on the western 

 wall of the bay. Upon the summits of some 

 small islands at the entrance of the bay, there 

 are also some remnants of terminal moraines, 

 formed by the glacier when it reached the 

 main channel ; that is, when it was some three 

 miles longer than now. 



The more recent oscillations, marking the 

 advance and retreat of the glacier within cer- 

 tain Hmits, are shown by the successive mo- 

 raines heaped up in advance of the present 

 terminal wall. The central motion here, as in 



