Champlain eras in New England. 207 
northward would have been greater, even if the surface increased 
in elevation in going north in New England. We shall not 
therefore be led into any great error, if we take the ratio of 
precipitation during our winters as a basis for deductions re- 
specting the Glacial era. 
e have made the thickness of the ice in the region of the 
watershed 12,000 feet, and that over the northern border of New 
England 6,500 feet. But, following the rate of winter precipi- 
tation, 2 to 8, the latter should have been not 6,500 but 18.000 
feet. The loss here indicated must have depended partly on 
an increased rate of flow over New England. In changing the 
surface slope from 10 to 24 feet a mile, the rate of flow would 
have been at least doubled ; and this alone would have reduced 
the 18,000 feet to 9,000. Again, the more southern latitudes 
would have had a greater amount of evaporation and melting, 
and it is possible that thus the rest of the excess—2500 feet— 
was removed. If the loss from the last-mentioned source were 
in the Canada region one-eighth and in northern New England 
a little over a fourth, the above difference would have resulted. 
Thus the contrast in the elevation of the glacier surface over 
the two regions may have existed without supposing the land 
of the watershed above its present level. hace 
The glacier probably extended in a southward direction at 
least 60 miles south of Long Island, where the depth of water 
18 hot over 250 feet; and perhaps 80 miles beyond where the 
depth is 600 feet, and then falls off dp iy The height of 
the by dae surface of the glacier along the Connecticut valley 
may be thus made the subject of calculations. The line of 
6,000 feet. elevation (which should have run at right angles to 
the direction of flow, except so far as temperature was a cause 
of divergence) passing Mount Washington, probably crossed the 
Connecticut in the region of Lyme or Hanover, N. H. The 
tance from this region to the limit 90 miles south of Long 
Island is about 310 miles; whence the mean slope of the upper 
surface of the glacier down the Connecticut valley should have 
been about 19 feet a mile. ies 
With this grade (supposing it a straight grade, which it would 
hot have been throughout, as the flow of the general mass was 
southeastward) we should have for the height in the region of 
Northampton and Mount Tom, 4,100 feet above the sea; of 
8 ringfield, 8,800; of Hartford, 3,400; of Meriden, 3,000; of 
height of the terminal cliff 90 miles south of Long 
here su posed to have been 200 feet. : 
The height of the upper surface of the ice over the — 7 
Part of Connecticut probably averaged 3,250 feet, which woul 
* See Author’s Manual of Geology, page 441. 
