from the melting of the Quaternary Glacier. - 191 
Below Windsor there is a prominent obstruction in Mount 
Barber, an elevation in the direct course of the stream and a 
mile wide; but there was abundant room for the river on either 
side of it. Another obstructing mass of ledges probably ex- 
isted just south of Turner’s Falls southwest of the mouth of 
Miller’s River, in Massachusetts, ten miles south of South Ver- 
non, where the Connecticut river makes a westward bend of 
six miles to Greenfield. This probably existing “‘mass of 
ledges,” is now: beneath the terrace formation, the top of which 
is the elevated plain between Montague City and Miller's river ; 
and its existence at no great depth beneath the plain is infer- 
red from the terrace deposits—on the ground that these are an 
indication of slackened flow in the waters. The flooded river 
passed both along the east and west sides of these obstructing 
ledges, as well as over them at highest water. After passing 
this place, the river at highest flood had an open and almost 
straight way to Middletown, which was nowhere less than 4,000 
feet in width, though narrowed at Mt. Holyoke, Enfield Falls 
and Glastenbury. 
Whenever a careful topographic survey of the Connecticut 
valley shall have been made, which shall lay down throughout 
it contour-lines corresponding to the maximum flood-level, it 
may be possible to arrive very nearly at the amount of resistance 
produced by the flexures. At present it is not possible to reach 
any accurate estimate ; and the best that we can do is to use a 
diminished width for the basis of the calculations and make 
a further allowance by estimate. The results with regard to 
the velocity are hence obtained below for the river with a 
breadth of 2,500 feet, as well as with that of 4,000 feet. 
he formula for the calculation of the velocity here em- 
ployed is that given by Humphreys & Abbot for large rivers 
in their admirable Report on the Mississippi River, numbered 
41, on page 312. It is applicable strictly to a limited portion 
of a large river without bends. It is as follows : 
v = ( (2257, st]4—0°0388) 
in which v is the velocity sought: s, the sine of the slope; and r, 
the mean radius = area of cross-section, a, divided by p+W, 
or the length of the wetted perimeter (p) plus the width at 
surface. In the general formula, the sine of the slope = s - 
/= length of limited portion of the river. h =h,+h,,= differ- 
ence of level of the water-surface at the two extremities of the 
distance /, in which h, = the part of h consumed in overcoming 
the resistances of the channel supposed to be straight and of 
nearly uniform cross-section, and h = the part of A consumed 
di 
in Overcoming the resistances of bends and important irregular- 
