232 



IRRIGATION. 



charge of the water, which include the pipes, the valve 

 tower, and the culvert. For convenience and safety, in 



Fig. 114. DAM WITH CULVERT AND TOWER. 



case of the giving way of a joint in the discharge pipe, 

 this should be carried out through a culvert of masonry, 

 of sufficient size to admit a man. This culvert com 

 municates with the valve tower as shown in fig. 114. The 

 _ _ ^^ valve is a circular plate, which 



slides between two flanges 

 within the pipe, the surfaces 

 which come into contact be 

 ing ground to fit accurately 

 together. This is raised by 

 means of a screw attached to 

 a rod having a horizontal 

 wheel for turning it at the 

 top. A form of valve frequent 

 ly used is shown at fig. 115, 

 the section of pipe contain 

 ing the valve being bolted by 

 the flanges to the discharge 

 pipe. A valve, in common 

 use in Italian and French ir 

 rigating works, is shown in 

 section at fig. 116. This, A, 

 may be made of wood, shod 

 at the foot with a plate of cast iron, ground to fit an 

 other similar plate attached to the opening of the pipe, E. 

 It is raised by the rod, B, keyed to the upper part, and is 

 guided by means of eyed wings, D, D, which work up 

 and down upon the rods, C, 0. 



Fig. 115. DISCHARGING PIPE 

 VALVE. 



