from the melting of the Quaternary Glacier. 201 
structions by bends or transportation, it appears that a slope in 
the water surface of only 0°383 inches a mile would give a 
mean velocity of 4 miles an hour; and one of 0°923 inches, a 
mean velocity of 5 miles. The Mississippi along a straight 
portion at Carrollton, during high water, when the maximum 
depth was 186 feet and the slope but 1:3 inches, has a mean 
velocity of 4 miles per hour. (See beyond.) 
Making allowance for the probable amount of resistance 
from the sources above mentioned, it would seem that a slope 
of 2 inches a mile to Springfield would have been sufficient to 
meet the conditions; and that one of 3 inches would have 
been too great. But suppose it 3 inches a mile; a change in 
the pitch of the valley amounting to 18 inches a mile would 
have been needed to produce it. If we suppose it 6 inches— 
which is a very large pitch in any stream under continuous flow 
(that is, not broken into parts by dams) which was the fact with 
the flooded Connecticut down to Middletown—the needed 
diminution in the pitch of the valley would have been 15 inches 
a mile. This amount, 15 inches, added to the 15 inches a mile 
deduced from tie elevated sea-beaches, would make for the total 
diminution in mean rate of pitch to Springfield 24 feet a mile; 
and if the amount were 18 inches, the total would be 22 feet a 
mile, which would make the change at Haverhill hardly 50 feet 
less than at Montreal. 
The later change, whatever its amount, would have been a 
continuation of the former. Whether it was confined or not 
to the Connecticut valley—a line of weakness in former geo- 
logical eras—must be determined by the study of other valleys 
to the east and west, especially the Merrimack on one side and 
that of Lake Champlain and the Hudson on the other. Itisa 
strange fact that the terrace formation of the southern part of 
the Lake Champlain region, and of its continuation along Lake 
George to Albany on the Hudson has not yet been carefully 
studied. 
In view of so great changes in the slope, reining in the 
va Carrollton is 121 miles from the mouth of the Mississippi, and at high water 
© surface of the river is 15-2 feet above sea-level. 
