192 J. D. Dana-—The Flood of the Connecticut River Valley 
ities of cross-section. In the equation for nik rivers, above 
quoted, h,, is thrown out by the condition 
he fo ollowing are the results for the peionn of the river in- 
dicated in the column to the left. The slope is given in feet 
per mile. The velocity is stated in miles per hour and in feet 
per second, and both for a width of 4,000 and 2,500 feet 
Velocity, width 4000 been 2500 feet. 
- pe I e 
Inm I In ft. per 
Slope hour Ss second 
oben to Windsor __. -.- Vico 13°07 19°16 12 ne 8:97 
sor to South V ernon ate ies 2°56 12°18 17°87 12-06 17°69 
ete Vern ringfield_____- 3°5 13°26 19°45 13°13 19°25 
Spring fiel Middletown dam_-. 1°25 = 10°23 15-00 10°12 14°85 
Haverhill to Middletown dam ____ 2°7 12°42 18°22 12°30 18°03 
South Vernon to Middletown dam oh 12:18 L737 12:06 17°69 
Middletown dam to the Sound____ 7-4 16°02 23°49 15°85 23°25 
From the above, the mean velocity for the whole river from 
Haverhill to Middletown, would have been, assuming that the 
relations of the land to the sea-level were the same as now, 
over 12 miles an ued even supposing the mean width to have 
been but 2,500 fee 
This oreat acy, or even one of 10 miles an hour, is not 
compatible with the character of the deposits which lie at dif- 
ferent levels beneath the surface of the stream—both those at 
140 feet below the surface and those at higher levels. The 
former, away from the region of the mouths of tributaries, con- 
sist almost uniformly of nearly incoherent but stratified sand, or 
any. rape and in some parts of clay ; and similar fine mate- 
ials in general constitute the terrace-deposits of the higher 
peels Pehadina the terrace-fronts) up toa level within 50 
feet of the highest flood level and often nearly to the upper- 
most plane. 
According to trials, a current of one-third of a mile per hour 
will take up and transport fine earth or clay having the parti- 
cles ‘016 inch in diameter; and one of two-thirds, fine sand, 
the mean diameter about ‘064 inch. Accordingly, since the 
mean diameter of the largest transportable particles varies as 
rey and Bazin, in their Recherches Hydrauliques, vate the so ielge as the 
stan velocity (in feet per second) at which scour commences for e different 
materials mentioned, and the corresponding calculated mean pi — 
Bottom velocity. Mean velocity. 
7. Marth cove tues 0°26 0°33 
Bi MOON: Coc eae bein ane 0°50 0°65 
WOMANS (oo Soe oe 1°00 1°30 
4. Gravel 2°00 2°62 
B POpDIOB Seve oS, Se 3°40 4°46 
on BLOHO 35256 4°00 5°15 
% he 6°5 
13°12 
—Cited from ee Encyl. Brit., vol. xii sass an Hydromechanics. 
