Perry.] 82 [February 3, 
may so express it, in a secondary relation to the original occurrences, 
and so to the restored edifice, which is supposed to answer to them. 
While this involves disadvantages, while it renders the work of re- 
construction more difficult, it is really no objection, in case the later 
materials on which we rely for evidence prove actually to be what the 
glacier-hypothesis implies they are. Thus this beginning of ice- 
streams perhaps properly constitutes the first stage of the Glacial 
period. 
§ 7. The Formation of the Ice-Sheet. 
Many local glaciers having come into existence in the manner sup- 
posed, it may be inferred that the way was at last prepared for the 
production of an immense field of ice. It is possible, if not probable, 
that there was little intermission in the- formation of the ice-sheet. 
Snows falling in winter all over the northern regions, and gradually 
coming to melt less and less during the summers, there would be the 
first steps toward a broad blanket of ice, which would be thickest, of 
course, in the more elevated regions and mountain valleys. The cold 
continuing to grow more intense, the work already begun must con- 
stantly advance. Snows still forming to some extent, whether so rap- 
idly as before or not, since the waste would steadily diminish, there 
would be in the aggregate a gradual increase in the quantity. The 
mass of névé receiving constant additions, we may presume that there 
was a perpetual augmentation of material, and that thus the several 
ice-sheets, or the thicker portions of a broad ice-sheet, experienced 
a proportionately rapid expansion and thickening. The many dis- 
tinct glaciers (and there must have been what was substantially their 
their equivalent) having their respective sources far up in the moun- 
tain fastnesses), would accordingly extend further and further down the 
valleys, and by degrees inosculate with each other. 
This process going on with little or no interruption, and there 
being less and less wasting of the ice masses, we may surmise that 
they were finally much prolonged. Thus they must have been thrust 
down into the p!1i13 in various directions to a great distance; from 
the White Mountains eastward, westward, southward, and perhaps 
northward; from the Green Mountains mainly toward the east and 
the west; and likewise from the Adirondacks, according to the nature 
of the region, and the various conditions which were there prevalent. 
Consequently the long valley now occupied by Lake Champlain and 
