36 BULLETIN 852, U. S. DEPAKTMENT OF AGKI CULTURE. 
the pipe line between the piezometer tube and the larger iron pipe 
(see PL II, fig. 3). 
While but three observations were made on this pipe the conditions 
were very favorable for test. The values of C s , about 0.330, are 
probably indicative of the silted condition within a smooth pipe 
rather than of the interior surface itself. (See values for Newell's 
tests, No. 24a.) 
_ No. 26, Experiment S-51.— 30^-inch jointed reinforced concrete 
pipe, Prosser pressure pipe, Sunnyside project, United States Recla- 
mation Service, Washington. — -Irrigation water is conveyed across the 
valley of the Yakima River by a siphon pipe of combination type. 
From the intake to a point 2,825 feet distant concrete pipe is used. 
The construction then changes to a wood-stave pipe 1 31 inches in 
diameter, which extends for an additional distance of 7,500 feet. A 
straight reach of the concrete pipe 2,276.3 feet long was chosen for 
test. Gauge No. 1, a water column attached to a piezometer tube 
of type A, was located about 500 feet from the intake, while gauge 
No. 2, a mercury column attached to a piezometer of type C, had been 
installed at the time of construction. A similar connection of type C 
had been placed near the upper end of the line, but was destroyed 
by the construction of a railroad crossing. It was necessary, there- 
fore, to drill a new hole through the pipe and use a connection of 
type A. The velocities were determined by timing solutions of 
fluorescein, injected at gauge No. 1 and withdrawn into a white-lined 
pan from a secondary connection to the pipe line located near the 
head of the wood-stave portion of the line, beyond the end of the 
concrete pipe. The slight difference in the area of the wood and 
the concrete line was considered in computing the velocity in the 
concrete line alone. The mean area of the pipe was taken as the 
mean of the areas of six units of the pipe remaining from construc- 
tion. It is quite certain that there was no sediment in the pipe, as 
the reach tested is on a continuous down grade and the operating 
velocities high enough to carry any debris on down to the sag of 
the siphon, which occurs in the wood-stave portion of the line several 
thousand feet beyond the concrete pipe. Examination of the line 
during the series of tests disclosed the scour at the upper end of the 
line (mentioned on p. 51), but showed a pipe free from slime or 
deposit at the upper end of the reach tested, and this condition 
undoubtedly held throughout the reach. The joints were not quite 
as nearly perfect as on the Victoria line (Nos. 30 and 31), and this 
probably accounts for some of the discrepancy in relative carrying 
capacities. As gauge No. 1 is located at an elevation approximately 
20 feet higher than that of the outlet, it is readily understood that 
only velocities higher than that which necessitates a loss of head of 
20 feet for the 2 miles of line beyond gauge No. 1 may be tested, 
because for all lesser velocities the pipe is not full at gauge No. 1. 
All concrete lines that serve as the intake ends of combination pipes 
are thus not subject to a complete test throughout a range of velocities, 
say, from 1 foot per second up, but can only be tested for the higher 
velocities. 
The concrete pipe was made in 4-foot lengths with an exceedingly 
wet mixture of 1 part cement to 6 of gravel. All gravel passed a 
quarter-inch mesh screen. Steel forms coated with a particularly 
Discussed as No. 35 in Bui. 376, U. S. Dept. Agr., p. 78. 
