lOO IRRIGATION FARMING. 



old creek bottom and almost entirely in coarse loose 

 sand. 



In construdling these surface storage basins the 

 dimensions are best when fifty by one hundred feet, or 

 one hundred by two hundred feet, etc., rather than of 

 square form. A pond that is fifty by one hundred 

 feet and containing five feet of water will irrigate 

 twenty-five acres, and the whole plant, including a 

 first-class wind engine, should not cost over $250. It 

 is a good rule to have the pond of such size that it 

 would not be necessary to empty it oftener than once 

 or twice a week. That would make the supply of 

 water at hand the main factor in determining the size 

 of the pond. It might readily be figured out in this 

 way : One gallon contains 231 cubic inches. A space 

 23.1 inches high, covering ten square inches, equals 

 one gallon, and one square foot, or 144 square inches, 

 14.4 gallons. Now divide the number of gallons 

 which can be pumped in three days' steady wind by 

 14.4, and the result will be the number of square feet 

 necessary for the bottom of a pond two feet deep, and 

 one-half that number will be sufiicient for one four feet 

 deep. 



Cementing. — To make a pond perfecftly imper- 

 vious for all time and give the best satisfa(5lion in the 

 end, line it with paving pitch or Portland cement. If 

 the latter, the preparation can be applied the same as 

 described in the preceding chapter on canal construc- 

 tion. The best coating for such work is a composition 

 of hot clean sand mixed with hot paving pitch, to 

 which has been added a percentage of crude oil resi- 

 duum, and the whole mixture applied hot, say at 



