DUTY AND MEASUREMENT OF WATER. 1 43 



inch head, while in other places the head is six inches, 

 there is evidently abundant room for variation, even in 

 the determination of the capacity of a single inch. 

 When, again, a number of inches came to be measured 

 at once, it became possible either to adopt an aperture 

 one inch high and the specified number of inches in 

 length, or to take the square of the whole number of 

 inches as giving the dimensions of the orifice, in which 

 case there is another great cause of variation. The 

 State Engineer of Colorado has calculated that the 

 miner's inch has been .026 cubic feet, or, roughly 

 speaking, a fortieth of a cubic foot, which is equivalent 

 to a flow of nearly nine gallons a minute, and this is now 

 generally adopted, though as a matter of fadt, in more 

 southerly states where water has been scarce, the 

 miner's inch has only meant one-fiftieth of a cubic 

 foot. 



An Irrigation Head. — The proper wetting of the 

 whole ground requires what is known as an irrigation 

 head. To irrigate ten acres with a miner's inch of 

 water needs from fifteen to thirty inches of flow at a 

 time, depending upon the porosity of the soil. A 

 single inch flowing constantly and used in that way 

 would not irrigate over two acres at che best, and'gen- 

 erally not over one-half an acre properly. But the flow 

 of a single inch without any reservoir to accumulate 

 it may be used in another way so as to produce fair re- 

 sults on from ten to forty acres, according to the nature 

 of the soil, the amount of rainfall and the kind of 

 trees — for it is only for trees that it can be used to 

 advantage. It would hardly pay to make trenches 

 around grape-vines on any large acreage, and although 



