J, LeConte— Ancient Glaciers of the Sierra Nevada. 1338 
nowhere did I see similar pebbles. Mr. Muir, who has walked 
around the lake, tells me that they do not occur on the eastern 
shore. We have, then, in the distribution of these pebbles, 
demonstrative evidence of the fact that Fallen Leaf Lake 
glacier was once a tributary of a much greater glacier which 
filled Lake Tahoe. 
he only other agency to which we could attribute this 
transportation is that of shore ice and icebergs, which probably 
id once exist on Lake Tahoe; but the limitation of the 
pebbles to the western, and especially the northwestern shores, 
is in exact accordance with the laws of glacial transporta- 
tion, but contrary to those of floating ice transportation—for 
lake ice is carried only by winds, and would, therefore, deposit 
equally on all shores. 
Again: I think I find additional evidence of a Lake Tahoe 
“mer de glace” in the contrasted character of the northern and 
southern shores of this lake. : 
found in great abundance boulders of enormous size, May we 
hot conclude that similar effects have been produced by similar 
. f h 
Principal flow of the ice-current was from the southwest, and in 
the fullness of glacial times the principal exit was over the 
by Lake alley glacier is perhaps more doubtful. All other 
Sierra lakes which I have seen certainly owe their origin to 
glacial agency. Neither do I think we should be staggered by 
the size or enormous depth of this lake. Yet, from its posi- 
