194 J. DP. Dana—The Flood of the Connecticut. River Valley 
two miles an hour at bottom; se is the condition in a 
stream having a mean velocity of 3 to 4 miles, 
The transported materials in we waters would have had 
a retarding effect; but small, since as rar shown, they 
were only ‘sand and finer material, and the fine straticulation 
indicates a free-flowing stream (p. 93). "the deduced mean 
velocity, over 12 miles an hour, could hardly have been 
reduced by all the causes of retardation together to less than 9 
or 10 miles an hour. 
We are thus led to enquire what range of evidence there 
may be as to the existence of a less pitch in the valley, to cause 
the less velocity, or as to any other method by which a dimin- 
ished velocity might have been produced. 
One method is by means of dams; a second, by changed rela- 
tions between the level of the land and sea. 
B. Dams on the Connecticut Valley as a possible source of less 
slope in the waters.—That it mE be understood ite is to be 
explained by means of dams, or in other ways, e 
view the facts with regard to the ley: deposits kad. aniociatad 
sand-deposits of the valle 
It is to be remembered that the sand-beds and those of finer 
material ordinarily make not only the lower terraces but also 
the highest, where tributaries are absent, to within 50 and 
often 20 or 30 feet of their tops; and that this is so even high 
up the Connecticut, as at Barnet, not two miles south of the 
junction with the Passumpsic, where these finer deposits ex- 
tended to a level of 150 to 200 feet above low water in the 
river. 
Clay-deposits are widely distributed about Hartford to a 
height of 75 feet and less above tide level, or Jow water in the 
river. At Springfield, 58 miles ina direct line from the Sound, 
they are of great extent at a height of 170 feet above the sea 
level ; at Holyoke, 8 miles north, on the west of the Connecti- 
feet; and over the Amherst region, as I learn from Professor 
Emmons, of Amherst, at nearly the same level. The dam 
below Middletown suggests a possible explanation of the origin 
of quiet water for the making of the clay beds about Hartford ; 
for if the dam were but little more than a third of its final 
height it would be sufficient; and if raised to within 10 feet of 
its full height, it might have produced the quiet movement in 
the waters required “for all the clay-beds up to and including 
those of the Amherst region. That the height of the dam was 
actually so near its extreme height, when the terrace deposits 
