46 BULLETIN 376, U. S. DEPARTMENT OE AGRICULTURE. 
within the pipe, are to occur. The capacity of this pipe was 9 per cent less than the 
discharge computed by the new formula. From the fact that the inlet is from a 
reservoir, and because the curves are very gentle, experience indicates that this 
pipe should have a greater capacity for a given loss of head than the new formula 
would indicate, although it is true that the interior condition v,f the pipe was not 
known. Two air valves at summits and one blow-off at a low point occur within the 
reach tested. The air valves are boxed to prevent freezing. 
No. 51, Expt. S-3, 144-inch Continous-Stave Douglas Fir Power Pipe 
Line, 1 Salmon River Power Co., New York. — About 4 miles from Altmar, N. Y., 
on the bank of the Salmon River, is located an hydroelectric plant, constructed in 
1913 and 1914 to carry a portion of the load formerly served by one of the big plants 
at Niagara Falls. Stillwater Reservoir is formed by a dam across the main channel 
of Salmon River about 2 miles above the power plant. A tunnel 600 feet long con- 
veys water from the reservoir to the upper end of a continuous-stave Douglas fir pipe 
line 144 inches (12 feet) in diameter. (PI. V, rig. 1.) At the end of 3,450 feet a taper 
transition section about 50 feet long leads into a similar pipe 132 inches (11 feet) in 
diameter. Tests were made on the 12-foot pipe. The portion of the pipe tested is 
without vertical curves, being laid on an even gradient Practically the lower third 
of the pipe is buried. No leaks worthy of notice occurred throughout the pipe. 
The line had been in operation but a few months, and since the velocities were high 
(up to more than 8 feet per second), it probably was in perfect condition on the inside, 
although it was not feasible to ascertain this. The stai'es are 4 inches thick. Taps 
for the nipples were made by a -j^g-inch wood bit until the tip of the bit punctured the 
inside surface of the pipe. The nominal area of the pipe was accepted as its true area. 
After making these tests the writer made careful measurements of a still larger pipe 
built by the same company and found the true area extremely close to nominal area. 
The discharge of the pipe, from which the velocity within the pipe was obtained, 
was determined in the following manner: As shown in Plate V, figure 2, after the 
water passes through the turbines it falls over a submerged weir into a tail-race 
channel which in turn discharges into Salmon River about a quarter of a mile 
below the power house. A good meter rating could be obtained, as the mean velocity 
for the greatest discharge was but 3.25 feet per second. This velocity did not cause 
a turbulent condition in the channel, since the latter had a hard, flat rock bottom. 
The form of the weir and the conditions of velocity of approach are such that the 
writer did not feel justified in accepting the discharge as computed from any known 
weir formula. The velocity of approach, in particular, is an uncertain quantity, 
since the bottom of the channel slopes up from 20 feet deep at the power house to a 
mean of but 1.234 feet deep immediately above the weir crest, within a horizontal 
distance of 220 feet. The weir is 79.6 feet long with end contractions approximately 
suppressed. It is a concrete wall 18 inches thick, rounded over on top. It is not 
designed as a measuring weir but for the sole purpose of drowning the draft tubes 
for all discharges. This weir was calibrated by making four careful current-meter 
measurements with as many discharges from a bridge across the tailrace below the 
weir; and meanwhile reading a hook gauge in a stilling box 8 feet above the weir and 
a tape gauge 3 feet below the weir. The latter gauge reading had no bearing on the 
calibration but was taken for the purpose of securing more information concerning 
submerged weirs. The results of these measurements follow. The elevations are 
based on a bench mark with an assumed elevation of 10.000 feet. 
i Eng. Rec, vol. 69, No. 24, June 13, 191-4, p. 671. 
