20 



TRANSPORTATION OF DEBRIS BY RUNNING WATER. 



high trough 13 feet above. In passing through 

 this trough it was first quieted by baffles 

 and then regulated as to surface level by 

 means of a spillway about 13 feet wide, the 

 overflow returning directly to the sump. At 

 the end it sank slowly through a vertical 

 shaft, or leg, whence it issued in a jet through 

 an aperture regulated by a measuring gate. 

 After spending its force against a water cushion 

 it passed through a stilling tank and then 

 through the experiment trough. From that 

 it fell a short distance to a settling tank, and 

 thence returned to the sump. 



In figure 2 the circuit is shown diagram- 

 matically but without accuracy as to the 

 arrangement and relative sizes of the parts of 

 the apparatus. 



Baffles 



DISCHARGE. 



For the control and determination of the 

 discharges used in the experiments, a measur- 

 ing gate was provided. Near the lower end 

 of the vertical leg of the high trough the water 

 issued through a rectangular opening in a 

 brass plate. The gate, also of brass, sliding 

 along the plate, controlled the size of the 

 opening, its motion being given by rack and 

 pinion and its position shown by a suitable 

 scale. The head was about 6 feet and was 

 determinate. The gate and its calibration 

 are described in Appendix B (pp. 257-259). 



The head was regulated by means of the 

 spillway in the high trough, and the amount of 

 overflow on the spillway was controlled by a 



FIGURE 2. Diagram of water circuit. 



gate valve in the supply pipe just above the 

 pump. As a check on the control, the posi- 

 tion of the water surface was shown in an 

 inclined glass tube outside of the high trough. 

 The index tube being nearly horizontal, its 

 meniscus had a magnified motion and the 

 condition of the head could be seen at a 

 glance. (See fig. 88, p. 257.) 



SAND FEED. 



Above the experiment trough, and near its 

 head, was a hopper-shaped box from which 

 sand was delivered to the current in the trough. 

 The box ended downward in an edge which 

 stood transverse to the trough. Along this 

 edge were a series of openings whose size was 

 determined by a movable notched plate of 

 brass. Water was supplied to the sand in the 

 hopper, both at the top and near the bottom, 



the amount being regulated by valves. This 

 water came from a small reservoir that was 

 kept full by diverting part of the jet issuing 

 from the measuring gate, and its use therefore 

 added nothing to the measured discharge. 



For some of the experiments debris was fed 

 by hand, the quantity being regulated by 

 means of a measuring box and a watch. 



SAND ARRESTER. 



The cross trough attached to the experiment 

 trough and extending below it (see figs. 1 and 2) 

 had along its bottom a track on which moved a 

 platform car. This car carried two iron boxes 

 to receive the sand. The boxes were rectan- 

 gular and a little broader than the experiment 

 trough. Openings protected by wire gauze per- 

 mitted water to drain from them when they 

 were lifted out. 



