40 BULLETIN 852, U. S. DEPARTMENT OE AGRICULTURE. 



too noticeable such a surface was wiped with thin mortar. Unless 

 pitted no wash coat was applied. 



The great amount of curvature was cared for by making three 

 types of bevel-end sections and making the degree of curvature for 

 each curve on the line such that one of the three types could be used 

 with a maximum bend of 3° at each joint. This limit could be 

 attained without inducing appreciable roughness within the pipe. 



As shown in Plate VIII, figure 1 , the various sections of pipe were 

 fitted together on the ground without the use of cement, a "soup 

 hole" being broken out of the top of each section just before fitting 

 the following section. The outside of each joint was banked up with 

 clay or stiff gravel to a point well above the spring line, in order to 

 prevent loss of grout. In cementing the joints the invert was 

 troweled from the inside. Then a band of spring steel 6 inches wide 

 was tightened against the interior of the joint and grout poured into 

 the soup hole from a coal bucket. When the grout had set the band 

 was removed and any necessary smoothing done with a trowel. The 

 writer examined the interior of this line and found the joints as 

 smooth to the touch as the rest of the pipe. Although this line is 

 not covered with earth, no expansion joints were inserted at the time 

 of construction, it being thought that the great amount of curvature 

 would automatically care for temperature changes. Experience with 

 this line during the winter of 1916-17 shows that it would have 

 been better to insert an expansion joint every few lengths of pipe. 



Siphon No. 1, between manholes 4 and 5, was chosen for the major 

 tests upon this line. It is longer than any of the other siphons and 

 near enough to the gatehouse so that alterations in discharge may 

 comparatively quickly reach the section under test. 



Holes were drilled through the top of the pipe near each end of 

 the siphon at such elevations that the pipe was completely filled at 

 these holes regardless of discharge. Piezometer tubes of type A were 

 thrust into the siphon through these holes. Water was turned out of 

 the pipe while the piezometers were carefully placed on the inside. 

 These tubes were connected with gauge glasses by means of which 

 the pressure head was read directly in water columns. 



Velocities were determined by fluorescein injected into the hole 

 in the concrete pipe made for piezometer No. 1 and observed through 

 the manhole in the flow line at the end of the siphon, beyond the 

 hole for piezometer No. 2. A correction was necessary for the 

 reason that the water did not fill the pipe for a few feet between gauge 

 No. 2 and the manhole. Data for this correction were carefully 

 taken with the level at the time the levels were run for the determi- 

 nation of the loss of head. 



As stated in the discussion under No. 54a, page 86, there is a weir 

 just above the intake to the pipe line. The crest is about one-fourth 

 inch thick, rounded .over on a radius equal to about one-half the 

 thickness of the plate. Water entered the chamber above the weir 

 from one side, making an indeterminate condition of approach 

 velocity. However, a float gauge was read for each run of water 

 and the discharge computed by the Francis formula. The com- 

 parison of the velocity in the siphon pipe as computed from this weir 

 discharge and as determined by the direct timing of color is given 

 in Table 2, page 18. It is to be noted that, for all runs, the velocity 

 by direct measurement is greater than as computed by weir discharge. 



