442 



IRRIGATION PRACTICE 



rise and fall of the water, is registered on a record sheet 

 that may be preserved for future use. (Fig. 162.) 



Where miners' inches are units of measurement, de- 

 vices like that of Fig. 163 are used. The United States 

 Geological Survey makes a cross-section of a canal or 

 river at a given point (Fig. 164) and determines the velocity 

 of the flow there, with current meters. (Fig. 165.) Many 



FIG. 16 6. Grant-Mitchell meter. 



special measuring devices are also available, as the Grant- 

 Mitchell meter. (Fig. 166.) 



Similarly, a great number of water divisors, in addition 

 to those mentioned in Chapter XVII, have been tried 

 out with varying success. 



A very great amount of work has been done by engi- 

 neers on the measurement of flowing water. The results 

 obtained are of high practical value. It must be said, 

 however, that the engineers, themselves, have not as yet 

 agreed upon the measuring device best suited to the use 

 of the farmer. Engineering books should be consulted 

 for further information on this subject. 



