THE FLOW OF WATER IN CONCRETE PIPE. 29 
locity as above determined with, that found by dividing the discharge 
by this mean area, shows agreement with the mean of the two meas- 
urements of 1.2 per cent. The discharge was measured over a 2-foot 
contracted, rectangular sheet-iron-crested weir, with end contractions 
greater than 2 h, bottom contraction about 5 feet, and Ji less than one- 
sixth of the length of the weir. The water welled up from the bottom, 
so that velocity of approach was negligible. This pipe was laid in 
1900. A comparison of the zone occupied by points representing 
this pipe with that of pipes 1, 2, 3, 4, 5, 9, 10, and 11 shows the 
progress made since the early eighties in the matter of smoother pipe 
pipe interiors and better joints, the value of C s for this line being 0.345, 
an exceptionally high value for " dry-mix" pipe. 
No. 8. Experiment $-53, — 12-inch jointed concrete pipe, J. W. 
Crane private lateral near Oakdale, Calif. — From one of the laterals 
of the Oakdale irrigation district water is conveyed down a gentle 
hillside to the fields by means of a concrete pipe line. A reach 1 ,850.8 
feet long was chosen for test, between the intake and an outlet 
hydrant in a riser pipe. The reach has one gentle curve in horizontal 
alignment and a slight sag near the far end. Water columns were 
used for both gauges, which were attached to piezometer tubes of 
type A. No. 1 was placed 4.4 feet down the pipe from the intake 
chamber, while No. 2 was thrust up into the line 6.4 feet from the 
riser pipe. Gauge No. 2 was a glass tube, while gauge No. 1 was a 
hook gauge noting the surface of the water in a stilling box. Thus 
a correction for capillarity was necessary in computing the elevation 
of the water column for gauge No. 2. Between the inlet and the 
second gauge are 21 riser pipes each 1 foot high, capped with a hydrant. 
The interior of the pipe was examined through several of these hy- 
drants and found to be clean of silt, but with rough joints between the 
2-foot units of pipe. The line was constructed by a man rather new 
in the business and the value of smooth joints was not appreciated 
as it now is in southern California. This is shown by the fact that C s 
is but 0.245. Measurements of the pipe interior through these hy- 
drants showed the average diameter to be 0.985 foot or that the area 
of the pipe was about 97 per cent of the area of a 1-foot pipe. The 
measured area was used in computations. Velocities were deter- 
mined by injecting saturate solution of potassium permanganate 
into the upper end of the line and observing the first and last appear- 
ance of the color at an open hydrant 55 feet beyond the hydrant at 
gauge No. 2. A few small leaks were evidenced by moist ground, 
but the use of color in determining velocities automatically takes care 
of any correction for such leaks, the velocity of the color dropping in 
proper proportion and at the proper time as each leak is reached. 
No. 9, Experiment $-24. — 16-inch jointed cement pipe, Irrigation 
Co. of Pomona, Calif . — A second reach of the same main pipe line dis- 
cussed as No. 10 was tested between boxes 91 and 92. This part of the 
line runs diagonally under an orange grove,, but, although it was laid in 
1 883 , roots have never interfered with the flow of water. It is straight, 
on a gentle down grade, and buried about 2 feet. There was one 
riser pipe in the reach tested. The nominal diameter was accepted in 
computing area and quantity of water (see No. 1, p>. 25). Except for 
run 1, both gauges consisted of hook gauges in stilling boxes, No. 1 
being attached by pressure tubing to a brass piezometer of type A, 
located 16.2 feet down the pipe line, while gauge No. 2 records the 
