142 IRRIGATION FARMING. 



running streams, as rivers or canals, the expression of 

 volume must be coupled with a fa<5lor representing the 

 rate of movement. The time unit usually employed 

 by irrigation engineers is the second, and the unit of 

 measurement of fiov^^ing w^ater is the cubic foot a 

 second, or the second foot as it is called for brevity. 

 Thus the number of second feet flowing in a canal is 

 the number of cubic feet which passes a given point in 

 a second of time. The cubic foot a second is the unit 

 of measurement usually adopted in the distribution of 

 water from or by the large canals of Colorado. A 

 quantity of water equivalent to a continuous flow of 

 one cubic foot a second, during.the irrigating season of 

 one hundred days, will usually irrigate from fifty to 

 sixty acres of land. It will often do more than this. 

 Another unit still generally employed in the west is 

 the miner's inch. This differs greatly in different 

 localities and is generally defined by state statute. In 

 California one second foot of water is equal to 50 miner's 

 inches, while in Colorado it is equivalent to 38.4 miner's 

 inches. In the following arrangement are given a few 

 convertible units of measure : 



I second foot = 450 gallons a minute. 



I cubic foot = 75 gallons a minute. 



I second foot == 2 acre feet in 24 hours— approximated. 



100 California = inches 4 acre feet in 24 hours. 



100 Colorado inches = 5^ acre feet in 24 hours. 



I Colorado inch = 17,000 gallons in 24 hours. 



1 second foot = 59^^ acre feet in 30 days. 



2 acre feet = i second foot a day or .0333 second feet in 3oday8. 



A miner's inch is supposed to define the quantity of 

 water flowing through an aperture an inch square, but 

 as in some parts the pressure adopted is that of a four- 



