81 [32j 
The lockage may. on so gi-cat a communication, be nearly equal 
to the possible operation of the canal; and if we suppose a boat to 
enter at eacli end every twelve minutes, or five per hour, and the de- 
scending boats passed at the same time, there would be ten falls pei- 
hour. 
The locks 90 x 15 x 8 — 10,800 
Plus ^ah, for waste, = 2,700 
13,500 
Per hour, - 135,000 
Per minute, - - , - 2250.00 
Per minute, total cubic feet, - - 57*37.80 
Per second, ... - ft. 95.63 
The fio wins; water at command, as before stated, - 48.28 
■o 
The requisite artificial supply per second, - - 47.35 
The next point in the investigation is, what body of water would 
ivftord this supply; what opportunities of forming reservoirs exist; and 
on what principles both such, and the feeders from them, arc con- 
structed ? 
That they would be filled, may be shewn from the known oper- 
ations of nature on these high grounds. 
The ratio of evaporation is a preliminary and indisj)ensab]e in- 
quiry. From a very extensive collection of facts, by philosophical 
observers in Europe, it a])pears that the ratio of evaporation from 
the surface of 7vater, in the summer season, is greater than the rain; 
but from land, somewhat less. To exemplify the first, it is ibund 
that, by observations at Salem, in the United States, the rain is 35 
inches, the evaporation 56 inches: at Baltimore, (by Mr. Brantz,) 
S9.83 inches: evaporation not observed in an open field. 
In England, the average of six years, 21.00 on the plane. 
25c 00 on an eminence. 
Idem, anollier series. 
. 
23.83 evaporation 
36.44 
Idem, in winter months, 
- 
11.48 
10.27 
Idem, in summer. 
- 
12.43 
26.17 
In Scotland, in wintcV, 
. 
14.19 
12.89 
In summer. 
- 
19.36 
31.51 
The well-known experiments of Dalton and of Hoyle, resulted 
in shewing the loss to be l-5th of an inch in 12 hours. 
There is a resemblance, in some i-espects, between the summer 
weather of England, and of the Allegany* in the temperature, an<l 
the frequency of showers. 
11 
