80 BULLETIN 852>, U. S. DEPAETMENT OF AGEICULTUEE. 
columns in graduated glass tubes, installed at each end of the reach 
tested. The relative elevations of these gauges were established by 
the static head; that is, with still water in the line. The piezometer 
connections were of type D (fig. 3), different from anything used in 
American experiments, so far as the writer is informed. A perforated 
brass ball, 30 millimeters in diameter, was set at the center of the 
pipe. In order to annul all influence of velocity head and secure 
only pressure head, the balls were filled with brass shavings. The 
usual tubing connection is made between the balls and the gauge 
glasses, through stuffing boxes set in the shell of the pipe. 
The volume of water was measured over a specially formed weir, 
having end contractions. 
Piezometer No. 1 was located about 1§ diameters from the intake 
of the pipe line. This would appear to be at a point subject to much 
disturbance. The weir is located about 8 or 10 feet below the power 
house and no mention is made of baffles to still the velocity of 
approach. These conditions may offer grounds for criticism of this 
series, although the platted points appear to be consistent with the 
exception of observation No. 3, which was excluded by the writer in 
consideration of this series, as there is probably some error of obser- 
vation or typography. 
No. 38, Experiment M-l. — 110-inch siphons, Catskill Aqueduct, 
New York. — The Catskill Aqueduct contains several pipe siphons 
using identical construction for inlet and outlet chambers and for the 
siphon proper. The latter is in essentials a steel pipe, lined with 2 
inches of cement mortar and protected outside with at least 6 inches of 
concrete. 1 
One siphon was lined with a cement-gun process while the others 
were grouted. For both processes, the invert, for a width of about 8 
feet of arc, was fined in the manner employed in laying sidewalks. 
When the cement gun was used the coat was applied in layers in 
rapid succession. Each layer is sufficiently rough for a secure bond 
with the next one. The resulting surface was floated and troweled 
to secure a smooth finish. The cement-gun process was abandoned 
by the contractor after one siphon had been so lined. In the grouting 
method, metal-covered wood forms were used after extensive experi- 
mentation. The grout was placed through a 2J-inch pouring pipe 
inserted in a rivet-passing hole and subjected to a head of about 4 feet 
above the zenith of the pipe. The first batch or two of grout for each 
set-up, 15 feet in length, was mixed 1 part cement to 1 of sand) while 
the succeeding batches were mixed in a ratio of 1 to 2. By both 
processes "very smooth interior surfaces were secured. " (See p. 82.) 
In Table 3 are shown average coefficients for observations on the 
Esopus, Tongore, Foundry Brook, Sprout Brook, Peeksill, Hunters 
Brook, Turkey Mountain, and Harlem Railroad siphons, for a flow 
of 350 million gallons per day (542 second-feet). Concerning these 
observations, made in August of 1915 under the direction of Mr. 
F. F. Moore, the board of water supply writes: 
The condition was not favorable for obtaining the best results on the pipe siphons. 
* * * The result of measurements of flow in pipe siphons was recorded as an 
lEngin. Rec, vol. 63, Apr. 15, 1911, p. 404; id., vol. 64, Sept. 16, 1911, p. 332; Eng. News, vol. 66, p. 526; 
Municipal Jour, and Engineer., Vol. 31, Aug. 23, 1911, p. 229: id., Dec. 7, vol. 31, 1911, p. 719: Jour. N. E. 
Water-Wks.Assn., Sept., 1911: Waterworks Handbook, by Flynn, Weston, and Bogert, New York, 1916, 
p. 323. 
