1872.) 117 [Perry, 
the discovery, I immediately engaged in its investigation. Guided in 
the study of the facts by the light which they afford, and by the sug- 
gestion of Professor Agassiz as very inadequately given by Sir 
Charles Lyell,1 I was soon satisfied that this beach should not be thus 
referred, but must be accounted for, if at all adequately, on other 
orounds. 
This so-called marine shore lies on the western slope of the Green 
Mountains, nearly 2200 feet above the existing level of the sea. 
Some miles to the west, there is another height called Hog Back, 
which is several hundred feet lower than Ripton Mountain. Let us 
now suppose the whole region covered by a sheet of ice; that it had 
passed its acmé; that it was already decidedly in its decline. As the 
ice slowly wasted, the summit of Ripton Mountain must finally come 
into view. ‘This process going on, we should expect the underlying 
drift, no less on the western slope than elsewhere, to be to some ex- 
tent laid bare. The detrital material, which in this place contains a 
considerable percentage of clay, was suited to retain water. Thus, 
as the thawing advanced, no break happening to occur in the glacial 
mass, a basin might be formed in the ice. This could have the 
mountain slope as its eastern side, and extending westward be there 
supported by the portion of the ice-mass which rested on Hog Back.? 
A stream, or possibly several glacial rivulets, flowing on the surface 
of the ice from the north, water would be supplied; while a beach 
might appear on the mountain side, the drift being washed, its angu- 
lar fragments rounded, and all its superficial matter sifted and sorted 
by the glacial lake, as is the case with many an inland shore to-day. 
Thus we should have a beach, not necessarily oceanic, having sand, 
rolled pebbles, and other water-worn materials as its characteristics— 
all these without any marine remains. The ice-sheet wasting very 
slowly, the icy banks of this glacial lake, after a considerable lapse 
of time, must disappear. Meanwhile the portion of the shore which 
rested on the slope of underlying drift might naturally remain to tell 
to coming ages its weird and strangely-fascinating story of a lake 
which was once perched high up on the mountain flank, extending 
out from its side perhaps for miles, hovering in space that is now mid- 
1 Principles of Geology (Am. Ed., 1855,) p. 87. 
1 Professor Agassiz tells me that there are many such lakes in the Alps, lying be- 
tween the glaciers and the rocky walls of the valleys. See also his Systeme Gla- 
ciaire. For an account of such lakes during the Ice-period, the curious reader is re- 
ferred to the paper by Professor Agassiz On the Parallel Roads of Glen Roy. 
