34 BULLETIN 852, TJ. S. DEPARTMENT OE AGRICULTURE. 
typical of present-day careful practice in the citrus groves of southern 
California where Ions;, well-made units are being used. The value of 
C s is 0.345. 
No. 20, Experiment S -57. — 24-inch monolithic pipe, Clavey siphon, 
Oakdale irrigation district, California. — As described under No. 28, 
the first portion of the Clavey siphon is 36 inches in diameter from the 
inlet to a "booster pump" which is used to force part of the water 
through 3,000 feet of 24-inch pipe to a point 8 feet higher than the inlet 
to the siphon. Tests were conducted on a reach 1,046.2 feet long 
between an air valve and a point 6.6 feet upstream from the outlet 
of the 24-inch pipe. Water columns attached to piezometer tubes 
of type A were used for both gauges. Velocities were determined 
with potassium permanganate solutions injected at gauge 1 and 
observed at the outlet. The color dragged out from 6.2 to 9.6 per cent 
of the time from moment of injection to the mean time of first and last 
appearance at the outlet, depending on the intensity of the injection. 
Although nominally a 24-inch pipe, the mean of 6 measurements made 
in the last 30 feet of the pipe indicates the actual diameter was 23.7 
inches, which was used in computations on this pipe. This pipe was 
constructed with wood forms, both inside and out. The longitudinal 
ridges made by the cracks in the boards, the circular ridge at the end 
of one setting of the forms and cemented concrete scraps are shown 
clearly in Plate II, figure 2, which was photographed from a point 
about 20 feet in the pipe at the outlet end. The values of C s are 
erratic, varying from 0.328 to 0.373. 
No. 21, Experiment $-47. — 24-inch jointed concrete pipe, lateral A, 
British Columbia Fruitlands Co., Kamloops, British Columbia, Can- 
ada. — A reach of lateral A pipe line 2,306.5 feet long was chosen for 
test. Water entered the pipe from a box similar to the one described 
under No. 16. Likewise the installation of the piezometers was identi- 
cal with Nos. 16 and 17. The first standpipe was located 64. 7 feet from 
the inlet of the pipe. Between the two gauges were located two turn- 
out boxes (not in use at time of tests), one 12-inch standpipe, and one 
waste valve. Water in the standpipe rose to the hydraulic gradient. 
The writer had been notified that the pipe was partially filled with 
gravel from the hillside above the main canal. A heavy rainstorm 
had eroded the hill, filled the main canal near the inlet and regulating 
box with gravel, and washed some of the latter into the pipe fine. 
The ratio between the measured size of several samples of this pipe 
and the true area of the water section was found in the following way: 
For one particular observation the velocity of the water through the 
reach was determined with two injections of color — one permanganate 
and one fluorescein. These agreed within 2 seconds in an elapsed 
time of 1,800 seconds. The quantity of water was determined by 
hook-gauge readings on the 3-foot contracted weir at the pipe inlet. 
The area was then found by solving the equation A=-y- The area 
thus found was 2.754 square feet or 87.5 per cent of the nominal area 
of a 24-inch pipe and about the equivalent of the area of a pipe 23.5 
inches in diameter. The mean value of C s is 0.252. 
No. 22, Experiment S-61. — 30-inch jointed concrete pipe, Temescal 
Water Co., Corona, Calif .• — Water for irrigation and domestic use is 
conveyed over a shallow depression by a siphon pipe 1,028 feet long, 
inserted between an open concrete-lined channel in sandy soil and 
