28 BULLETIN 852, U. S. DEPARTMENT OF AGRICULTURE. 



easily whenever the current carried it against the periphery of the 

 pipe, rather than lurch back into the current, as would a more 

 irregular float. The maximum variation in time of any one float 

 from the mean time of all of the floats was about 5 per cent. In 

 connection with tests on pipe No. 7, floats of this type agreed with 

 the velocity as determined by a well-made, contracted, rectangular 

 weir 2.005 feet long within 1.2 per cent. At the intake a nook 

 gauge in a stilling box determined the pressure head at the piezo- 

 meter tube (type A) located 10 feet down the pipe. At the outlet 

 a similar tube was held 1.6 feet in the pipe against the current. The 

 pressure head at this tube was read in a water column beside the 

 riser pipe. This pipe was laid in 1885 and appeared to be per- 

 fectly clean. As it is in an open field there is no chance of roots 

 choking the interior. The nominal diameter was accepted in com- 

 puting area and quantity of water (see No. 1, p. 25). The value of 

 C s varies with the velocity, from 0.244 to 0.278. 



No. 6, Experiment S -33. —12-inch jointed cement pipe, San An- 

 tonio Water Co., Ontario, Calif. — This pipe lies between two division 

 boxes and extends under a wash located north of Twenty-fourth Street 

 and west of Euclid Avenue near Ontario. Though too short for experi- 

 mental purposes, if low velocities are to be considered the 227.5 feet 

 between the boxes is ample when the commercial velocity, nearly 

 6 feet per second, is obtainable. Water columns were used at both 

 gauges. These were attached to piezometer tubes of type A, No. 1 

 being placed 7.7 feet in the pipe from the inlet chamber and No. 2 

 being held 2 feet up in the pipe from the outlet chamber. Velocities 

 were computed from the mean time of four batches of fluorescein, 

 timed from the instant of injection at the inlet to the mean between 

 the first and last appearance at the outlet. Just four seconds (by 

 test) was required for a given body of water to pass through the 

 length of hose under a head of 1 foot. This head is of course the 

 difference in elevation between the surface of the water in the 

 chamber and the outlet of the hose. The nominal diameter was 

 accepted in computing area and quantity (see No. 1, p. 25). 



This pipe line was laid in 1911. The units are 2 ieet long, made 

 with a dry mix tamped into steel molds and afterwards washed on 

 the inside with cement grout. The line is buried 2 or 3 feet and is 

 straight but for a slight sag under the wash. The value of C s , 0.322, 

 shows the marked improvement in joints in pipe line laid in recent 

 years. 



No. 7, Experiment S-27. — 12-inch jointed cement pipe, San An- 

 tonio Water Co., Ontario, Calif. — A straight, level reach of lateral pipe 

 on Fourth Street, Ontario, was chosen for this test. Water enters the 

 pipe over a division wall in a sand box and leaves it at the bottom of a 

 similar sand box on the corner of Fourth and Euclid Streets. Piezo- 

 meter tubes of type A were used at both ends of a reach 869.4 feet 

 long. The pressure head at gauge 1 was read in a water column 

 beside the sand box, while that at the outlet piezometer was read by a 

 hook gauge in a stilling box attached to the piezometer by pressure 

 tubing. Piezometer No. 1 was 4.7 feet from the inlet and No. 2 was 

 1.9 feet from the outlet. The mean time of six weighed orange floats 

 like those described under No. 5 was used in computing the velocity 

 of the water in the pipe. Accepting the mean area of samples of pipe 

 of this size in the pipe yards oi this company and comparing the ve- 



