95 [ 82 1 
its lowest slate. His reply was, that in a dry season, such as we had 
lately had, there was just enough to carry his two grist mills. The 
measure of his flumes, compai-ed with tiic result of a measuremoit of 
the water as now flowing, would give the minimum and the medium 
quantities. Each gate w:is fouiul to he 33 inches wide, its hoist 4^ 
inches, head of water 3 feet. According to the formula of DuBerat 
and Dr. Robinson, tlie quantity discharged is thus found: depth to the 
centre of gate 3.188 feet; tiie square root of which being 1,785, whidi 
multiplied by 8.02 x (by area) 1.03x82 (vena contracta), gives cubic 
1,000,000,000 ""*" 
feet 12.093 per second. 
12.093 the same for the other gate. 
24.186 feet is therefore the minimum quantity. 
The race was found to measure at its entrance 7 feet ia width, and 
2 feet deep, the Aelocity 100 feet in 80 seconds, which, according to, 
Pi'ony, is 14 feet. 
According to Du Berat, 1 3. 56 
27.56 
The mean of which is 1 3.78 per second. 
The discharge over the dam was at tiiis time three inches deep, 
180 lectin length, which according to the formula given in Rohinson*s 
Mechanical Philosophy, is 2.226 x 180 x 12 == 61. =80.136 feet. 
Or by another formula, 5.19, the square root of the 
cube of the depth, x 180 x 12 x 11.50 =74.600 
154.73G 
The mean is 77.368, and plus 13.78, gives present medium quanti- 
ty 91.143 fact at Hildebrand's mill, which is almost foiir tiaies the 
minimum delivery. 
The next day the gentlemen who were ascending the river reached 
Johnstown, and, proceeding up the Little Conemaugh, measui-ed tJie 
stream at the forks, about six miles as the stream runs above the mill. 
The south fork was found to contain 43.87 feet 
The north fork 59.02 
102.89 
The evaporation in the course of that six miles very w ell accounting 
for the difference. 
The whole party having joined at Ebenshurg, excepting Colonel 
Totten, whose militaiy duties had called him away, wc pi-ocecded to 
measure those streams which arc nearest the top of the mountain, ai' 
those of them which were most immediately relied on. 
