Submergence in the Narragansett Bay. — Fuller. 3 1 5 
island is fifteen miles. The plain in the vicinity of the cove 
indicates water standing at least fifty feet above the present 
sea level. It follows, therefore, that the average surface slope 
of the assumed torrent would have been at least three and a 
third feet per mile. Taking this as a basis, the velocity and 
discharge of the two principal outlets of Narragansett bay 
were computed according to the formula given by Hum- 
phreys and Abbot.* The widths and depths of the outlets 
in their flooded condition were calculated from the sound- 
ings and contours of the chart before mentioned. The results 
obtained were as follows : 
Eastern Passage. 
W= width=n,5oo ft. A=area of cross section=Q58,4oo sq. ft. 
p = wetted perimeter=Wx 1.015=11,672 
h A.Z?. 
s = sm or slope= y = jTg^ = .0006313 
r = hydraulic mean radius = " .,. = 41.36 
v = velocity. D = Av = discharge. 
v = ( [225 rj'^^s^. 0388) 2. -13.95 
D (approx.) == 13,370,000 
Western Passage. 
W= q,6oo A = 388,800 p = 9,744 
s=. 0006313 r = 20. II \- = 9. 574 
D (approx.) =3.722,000 
Combined discharge = 17,092,000 cubic feet per second. 
The combined discharge, as has been seen, would have 
reached the enormous figure of over 17,000,000 cubic feet per 
second, or nearly twenty-eight times the discharge of the Mis- 
sissippi river, and equivalent to 280 glacial streams of the size 
mentioned.! 
Great as this flood appears, however, it is considerably less 
than would actually have been the case if the Champlain 
waters stood at a hight of fifty feet above the present level 
in the vicinity of Greenwich cove. The discharge at any 
point on the bay below this cove (which marks the probable 
*Report upon the Physics and Hydraulics of the Mississippi River, 
(Professional Papers of the Corps of Topographical Engineers, U. S. 
Army), Edition of 1878. 
tThe velocity of the glacial stream as indicated by its pebbles, is 
t:iken as six feet per second. 
