354 



IRRIGATION PRACTICE 



crest, some distance back from the weir itself, where the 

 overfall has not yet begun to curve the water downward. 

 Then, by the use of tables (See Appendix B), the quantity 

 of water in cubic feet a second passing over the weir 



FIG. 99. Details of Cippoletti weir. 



may be determined. Moreover, by use of these tables 

 the size of the weir necessary for a given flow of water 

 may be found. (Figs. 98, 99.) 



However, even the use of tables is somewhat unsatis- 

 factory and inconvenient for the farmer actually at work 

 in the field. For that reason, plates have been devised, 

 that may be screwed to the side of the weir box, which 

 show by inspection the number of cubic feet of water 

 passing over the weir every second of time. (See Fig. 100.) 



