76 IRRIGATION FARMING. 



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 

 divine, 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 sufficient for one 

 four feet deep. 



Cementing. To make a pond perfectly impervious 

 for all time and give the best satisfaction in the end, 

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

 latter the preparation can be applied the same as de- 

 scribed in the preceding chapter on canal construction. 

 The best coating for such work is a composition of hot 

 clean sand mixed with hot paving pitch, to which has 

 been added a per cent of crude oil residuum, and the whole 

 mixture applied hot, say at about 300 degrees, and spread 

 much in the same way as the asphalt coating is applied up- 

 on streets. This mixture could be used while hot as a 

 mortar and spread with a trowel or with a flat shovel. If 

 spivad smoothly and evenly while hot and with as much 

 pressure as possible to make it compact, it would soon 

 set and form a coating that would give more or less with 

 the settling of the ground, that would be absolutely water- 

 tight and that would not deteriorate under the chain:'- 

 of temperature. The paving mixture itself comes in 



