The Retreat of the Glacier. 361 
. 
general conclusions can be looked for 
_ CL.) Drainage-area.—The present drainage-area of the Connec- 
ticut, north of Massachusetts, covers about 8,500 square miles; 
»etween the northern Massachusetts line and Hartford, 2,10€ 
square miles; and between Hartford and the Sound, 450 square 
miles; making in all 11,050 square miles. The Hartford limit 
is here made to extend south of Hartford on the west, so as to 
include the whole drainage-surface of the Farmington River, 
which joins the Connecticut north of Hartford. The area cov- 
ered by the Quinnipiac River might also be added, since the 
overflows from the Connecticut River valley, at Northampton 
and south of this point, so far as they emptied into the Sound 
‘by a separate outlet, reached it by the Quinnipiac valley. But 
the area is not over 50 square miles. 
(2.) Amount of ice over the drainage-area.—The mean thick- 
ness of the ice in and west of the White Mountain region, judg- 
ing from the glacial scratches on the White Mountains, and on 
Mt. Mansfield of the Green Mountains, was probably about 
9,000 feet; at the sources of the Connecticut River, 75 miles 
north, on the borders of Canada, at least 6,000 feet; and to the 
south near the Massachusetts border, not far from 3,500 feet. 
The mean thickness for the whole area, 8,500 square miles in 
extent, thence deduced, is about 4,500 feet ; and, if so, the whole 
amount of ice covering the drainage-area north of Massachusetts, 
at any one time before melting had made much progress, would 
have been about 7,250 cubic miles. 
quantities connected with this subject, and -only some very 
across the Sound, and landed large bowlders, some of more than 
a hundred tons weight, with a large amount of moraine material 
(referred to the terminal moraine) on the south side and other 
parts of Long Island; and the chief part of the fall necessary 
for motion came from a northward increase in the thickness of the 
ice, the Sound being a shallow trough 20 miles or so wide. 
slope of 0° 25’ would give a pitch of 38°39 feet per mile 
(= 1:137°5), and make the thickness along a line 34 miles 
north-northwest from the south side of Long Island, 1305 feet ; 
and one of only 0° 20’ would give a pitch of 30°72 feet per 
mile (= 1:171°8), and a thickness of 1,044 feet.* On the 
above assumption the amount of ice in this part of‘the drain- 
* In Greenland a thickness of more than 900 feet exists according to Helland, 
at the very end of the Jakobshavn glacier, this being proved by the thickness of 
the icebergs broken from it. 
