200 J. D. Dana—The Flood of the Connecticut River Valley 
is shown to be improbable by the coarse character of the deposits 
in the Springfield region that were made at maximum flood ; 
mean tide at 
PIV OTE es re ee oe te So 387 feet. 
WelGGOt oro eg Le er el eee SOF. + 
South Vernon Sub iy Aira ts ray. 2 Se 
Springfield 1Di os 
The Middletown damwn__..__.. 144 * 
Excepting south of Springfield, the changes in slope thus in- 
troduced between the places mentioned are small—that from 
South Vernon to Springfield becoming 2-2; from Windsor to 
South Vernon 1:2; that from Haverhill to Springfield, 1°8; and 
that from Haverhill to Windsor continuing at 2; so that the 
velocities would be but slightly altered. Between Springfield 
and Middletown the pitch becomes about 8 inches a mile. 
According to the preceding table, the velocity from Haver- 
hill to Springfield, notwithstanding this change of one-third in 
the slope of the stream, would still, when at the highest flood- 
level, have exceeded 10 miles an hour for a mean width of 
2500 feet, the pitch to Springfield being nearly 2 feet a mile.* 
And if we assume that bends and other obstructions, and trans- 
portation would have reduced the mean velocity 20 per cent, 
it would still be 8 miles an hour, with a bottom velocity over 
6, and: therefore much in excess of that indicated by the char- 
acter of the bottom deposits. 
It is quite certain that the slope must have been much less 
than that which corresponds to a height of water-surface at 
Haverhill of 387 feet, or a pitch in the valley to Springfield of 
21 inches a mile. But it is not so evident what slope would 
harmonize the facts; that is, would cause a velocity sufficient 
to make or leave coarse valley deposits near and at flood level, 
such as might be made by a current of 4 to 6 miles an hour, 
and, at the same time, leave almost undisturbed beds of sand 
or of fine pebbles along its bottom, whether at depths of 50 or 
150 feet, this alike for the stream north of South Vernon and 
south of it, and even for the part north of Wells River to 
Barnet as well as south of Wells River. . : 
By calculation, using the same elements as before, taking 
the width at 2500 feet and making no allowance for ob- 
* According to the formula, the velocity varies approximately as the 4th 
root of the slope, and, consequently, to diminish the velocity from any rate to one- 
half, the slope must be reduced about a sixteenth. 
S 
if 
4 
; 
