78 BULLETIN 376, U. S. DEPARTMENT OF AGRICULTURE. 
the line. Henny states x that too much reliance should not be placed on this test as 
" the only method at hand to determine the flow was from frequent determination of 
velocity by means of vertical floats in a semicircular flume at the upper end of the 
pipe. ' ' This test was not used by Williams-Hazen, Moritz, or the writer in the deriva- 
tion of their formulas. The friction factor found indicates a capacity greater than the 
average. According to Henny 's report in the Reclamation Record for August, 1915, 
this pipe is still sound ' ' except some deterioration where covered with loose rock only. " 
No. 33. Rectangular Unplaned Poplar Pipe. — Tests on an experimental pipe 
2.624 feet wide and 1.64 feet deep were made in France by Darcy and Bazin. As the 
pipe is similar to that described as No. 22 the same discussion applies to both. (See 
page 76.) 
No. 35. 31-inch Continuous-Stave Douglas Fir Siphon Pipe, Prosser Pipe 
Line, Sunnyside Project, U. S. Reclamation Service, Washington. — In the 
discussion of the Moritz tests J. S. Moore gives the details of experiments conducted 
by him on the Prosser pressure pipe. Irrigation water is conveyed across the Yakima 
Valley over the Yakima River in a pressure pipe of combination type. A concrete 
pipe 30| inches in diameter is used until the head reaches about 45 feet, at which 
point the line is changed to a 31-inch stave pipe. The reach tested has but one 5- 
degree curve, for about 19 degrees of central angle, located near the outlet end. At 
the river the maximum head is about 105 feet. The tests were conducted in August 
and October of the first irrigation season after the pipe was finished, the highest 
velocity being obtained only in August. Before backfilling, but following recinching 
of bands, external diameters were measured every 50 feet. The discharge was ob- 
tained from the rating curve of a 6-foot Cipolletti weir, the curve having been ob- 
tained by calibrating the weir against current-meter measurements from a meter sta- 
tion near the weir. The capacity of this pipe was about 6 per cent less than the dis- 
charge computed by the new formula. From the fact that the feed canal is down a 
very steep grade in a natural channel for part of the distance it appears to the writer 
that the pipe might very easily contain sufficient debris to account for any deficiency 
in capacity. 
No. 36.— This is another reach of the same pipe as that last described. These 
tests covered a shorter piece, included in the long reach tested as No. 35. The two 
runs made at the highest velocity, in August, showed the same loss of head per unit of 
length in both reaches of pipe, but the other runs, made in October, gave divergent 
results, as shown on Plate VI. Mr. Moore states that he is not prepared to explain 
this divergence. This series of tests indicate that the capacity is 10 per cent less than 
the discharge computed by the new formula. (See discussion of No. 35.) 
No. 41. 44^-inch Continuous- Stave Douglas Fir Pipe, Municipal Water 
Supply, Seattle, Wash. 2 — T. A. Noble conducted a series of tests on a 44-inch pipe 
at the time the tests on the 54-inch pipe (discussed as No. 44, p. 79) were carried on. 
With the exceptions noted below the same general methods were used on both pipes. 
The horizontal curves in the 44-inch pipe were so flat that for all practical purposes 
the pipe may be considered straight. For about one half the total reach the pipe 
follows an even gradient. For the other half it crosses a depression about 10 feet in 
maximum depth in a distance of about 2,000 feet. Thus, practically, the pipe is with- 
out curvature in either plane. After passing through the reach of 54-inch pipe dis- 
cussed as No. 44 the water enters a settling basin. From this basin it is conveyed in 
the 44-inch pipe now under discussion. Water columns were used for both gauges. 
Gauge No. 1 was located 150.6 feet downstream from the inside wall of the basin. 
Gauge No. 2 was located 4,041 feet farther down the pipe line. No growth appeared 
within the 44-inch pipe; according to Noble the higher velocities in the 44-inch pipe 
i Journal Assoc. Engin. Socs., 21 (1898), p. 250. 
2 Trans. Amer. Soc. Civ. Engin., 49 (1902), p. 113. 
