202 J. D. Dana—The Flood of the Connecticut River Valley. 
the report of Humphreys and Abbot as one of the thirty cases 
upon which data their formula for velocity was based, the ele- 
ments were as follows: 
Area of Wetted Maximum Mea 
cross-section Width perimeter wy hn v locity 
in square feet. feet. in feet. in feet. per second. lope. 
93,968 2653 2693 136 5'9288 0:00002051 
The calculated velocity found by the formula was 5°9673 per 
second, giving a difference of 0°0385 feet. The velocity obtained 
is almost exactly four miles an hour; and the slope to w te this 
velocity corresponds is, as already stated, 1-3 inches per m 
eans of the fo rmula, we have, from th scnai tions 
in the Mississippi as to dimensions, but with other acciak slopes, 
the following results 
Slope per mile Velocity in Velocity in feet 
in feet. Slope per foot. miles per hour. per second. 
0°00033 : 11918 
3°0 0°0005682 13°670 
45 0°0008523 10°32 157145 
6°0 0-0011364 12°47 18-292 
The case of the Mississippi differs from that of the flooded 
lei ig in the less average depth—the maximum being 136 
he Mississippi River was more like the New England 
i when it was itself flooded from the same cause; when its 
less deposits were formed, according to Professor E. W. Hilgard, 
not many miles above the head of the delta, to a height of 450 
feet above the sea. Its average width below the mouth of the 
Ohio exceeded 50 miles. Professor Hilgard points out the fact* 
that the “Grand Gulf Group,” of the border of the Gulf of 
e 
stratified arift to a ant ot of 500 feet above the Peulf; and that 
the facts berate that an elevation of the gulf f border, and of that 
portion of the Mississippi valley, was begun in the earl y Ter tiary 
and — on until it had re — a height in the Glacial te of 
900 feet, after which ther reverse movement. In t 
reverse sameness (or after it yee a yor bend upward), pod region 
must have been long at or near 450 above the sea (if there was 
not, in ‘are of part of it, a diminution of pitch northward), in 
order that ne slope of the water-surface of the river should have 
been yt 
as the le 
On this view, the Mississippi had a dam, and ~~ put thereby 
into a lacustrine condition, right for making less or loamy depos- 
its. The Connecticut had a dam also; Sing it couanned neverthe- 
less to be a river throughout, its loa deposits and clay-beds 
being “saboniinasen in the upper Sevtnen | to its sand-beds and those 
of coarser constitution, 
* Tn this Journal, xxii, 58, 1881. 
[Lo be continued.] 
to a minimum, so as to allow of such fine deposits 
