DUTY AND MEASUREMENT OF WATER. 



55 



feet a second or .04 for the acre feet a day, or by 0.5 

 for the acre inches a day, or by 4 for the acre feet in 

 100 days, or by 9 for the gallons a minute. 



THE CAIylFORNiA WEIR TABI,E 



Gauging Large Streams. — Frequently it is im- 

 possible to construct even a temporary weir on account 

 of the large quantity of water the stream carries. 

 Measurement must therefoi-e be made by other methods, 

 one of the simplest of which is to ascertain the mean 

 velocity of the stream in feet per minute. Next ascer- 

 tain the area or cross-sedlion of the stream in square 

 feet. Having learned these two quantities their prod- 



