8S C 32 1 
iSea^ the other on the low ground, 20 feet only above tlie sea. The 
series of observations extended through the course of tive years, 
1814 to 1818; when it resulted that there fell, irt a year, upon the 
plain, 23.66, upon the hill, 41.49 inches, nearly as 5 to 8. 
The past summer, in the month of June, there was, on the Alle- 
gheny, a copious fall of rain, which raised Deep Creek nine feet. 
But, from the 4th July to 17th August, there was little, and then 
quite a freshet; but it was again Ji dry time in September. 
We return, therefore, to the extent or capacity of reservoirs re- 
irjuisite to the quantity of water deficient for the longest line> sixty 
miles: 
Deficiency 47.35 cubic feet, x 60 x 60 x 24 x 60 days = 245,462,400 
cubic feet. 
To provide for this quantity, under the supposition of its being re- 
quisite for 60 days, we have the following places, which if flowed 
to the depth of six feet above the level required for feeders, whose 
slope shall be sufficient to carry the water to the canal, with an allow- 
ance above that of one foot, for evaporation, and two feet for filtra- 
tion, will cojitain available quantities as follows, according to the re- 
port of the surveys, viz. 
1st. On the Youghiogeny, above the mouth of Cherry tree branchy 
by a dam, which, measured from the surface of the stream to 
the surface of the reservoir, will be, besides the submerged 
part and the foundation 19 ft. 149,131,000 
«2d. On Cherry tree Creek, 19 ft. 85,494,000 
Sd. On the Youghiogany, from Cherry tree to 
Snowy Creek 29 ft. 75,506.000 
4th. On Snowy Creek, including Laurel, 29 ft. 176,490,000 
5th. On Youghiogeny, from Snowy Greek dam to 
Little Youghiogeny, 44 ft. 1 50,000,000 
6th. On the Little Youghiogeny, 44 ft. 200,000,000 
Cubicfeet, 836.721,000 
This quantity appears to be treble that required, nor have we in- 
cluded those reserves which might be formed on the Deep Creek and 
Glades; nor that of which the Pine Swamp, west of the Youghioge- 
ny, may be capablt;; nor one which might possibly be formed by a 
dam 90 feet high, above the Great Falls. 
The four first are the most practicable, and they would have a feed- 
er of about 16 miles in length. 
It is not to be denied, in practice, that the principles which should 
govirn the construction oi feeders are in some obscurity: with the ut- 
most precaution they have sometimes disappointed expectation. That 
of St. Prive, on the canal DeBriare, is eleven miles in length, and 
it lost three fourths of the water that entered it, although the feeder 
was rebuilt with every possible ])recaution, except covering it. The 
usual section of the stream at the entrance gate was 5 feet broad and 
