I50 IRRIGATION FARMING. 



cross-se(5lion, which is not the case even in a uniform 

 chamiel, and is much less so in one irregular or in 

 poor repair. Such a division is to the disadvantage of 

 the smaller consumer. The nearer the velocity is uni- 

 form across the whole channel the better this method 

 of division. Accordingly, means are frequently taken, 

 by weir-boards or otherwise, with this objec5l in view, 

 but generally with indifferent success. A screen would 

 y, ^ accomplish this one obje(5l better, but 



the objedlions to its use are too many 

 in most places to render it pracflicable. 

 Fig. 40 represents one of the most 

 common fotms of divisors. The par- 

 tition board (A) is movable, and may 

 _ be placed at different distances from 

 the side ( C) , so that the user can vary 

 the proportion of water which he re- 



ceives. A cleat of some kind is often 



used to prevent the board from being 

 moved beyond a certain limit. Where 

 FIG. 40— DIVISOR. ^^^ ditch is wide and shallow there 

 is sometimes a simple truss used with 

 a depending cleat. Sometimes a wire or chain restridls 

 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 movable 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. 



Module or Measuring Boxes. — The measuring 

 box has for its obje(5l the proper apportionment of 

 water to each consumer, so that he may depend upon 



