116 



IRRIGATION FARMING. 



The partition board (.4) is movable, and may be placed 

 at different distances from the side ((7), so that the user 

 can vary the proportion of water which he receives. A 

 cleat of some kind is often used to pre- 

 vent the board from being moved beyond 

 a certain limit. Where the ditch is 

 wide and shallow there is sometimes a 

 simple truss used with a depending 

 cleat. Sometimes a wire or chain re- 

 stricts the movement. In these cases 

 it is usually assumed that the amount 

 of water going to the side channel is 

 in proportion to the distance the mov- 

 able partition is from the side, and the 

 ratio is the same to the distance across 

 as the volume is to the volume in the 

 whole ditch. 



FIG. 39. DIVISOR. 



Module or Measuring Boxes. The measuring 

 box has for its object the proper apportionment of water 

 to each consumer, so that he may depend upon receiving 

 a definite quantity from the main ditch. The method 

 of measurement gaining in favor in the West is by means 

 of a hydrometric flume. One of the most ingenious and 

 satisfactory for use on small distributaries is that in- 

 vented by Mr. Foote. The chief fault of this apparatus 

 is the fact that it measures water by the inch instead of 

 by the second foot. This unit of graduation can of 

 course be changed. Its merit consists in the circum- 

 stance that it renders it possible to maintain very nearly 

 a standard head, as shown in Figure 40. It consists of 

 a flume placed in the main lateral (^4), and a side flu mo 

 (B) in which is constructed the measuring gate, while 

 opposite to it is a long overfall ((7), the hight of which 

 is used as to maintain a standard head above the meas- 

 uring slot. Such a weir is cheaply constructed and 

 easily placed in position, and costs but a few dollars for a 



