266 IRRIGATION FARMING. 



of operation is merely nominal. A good windmill plant 

 with a reservoir large enough to irrigate ten or fifteen 

 acres need not cost to exceed three hundred dollars 

 originally, and such an installation would last for years. 



Capacity of Pumps. The quantity of water a 

 windmill will lift into a reservoir during an average of 

 eight hours' run a day depends entirely on conditions. 

 If a mill of a given capacity has to lift the water from a 

 considerable depth, it cannot raise as much as if the 

 water is lifted only a few feet. For this reason, in the 

 latter case a larger sized pump may be operated by the 

 same force exerted on a smaller size, when the water is 

 taken from a considerable depth. 



Theoretically, one horse power will raise a five-inch 

 column of water one hundred feet, a six-inch column 

 seventy feet, and an eight-inch column forty feet ; addi- 

 tional horse power will elevate the water in direct pro- 

 portion. A ten-foot mill will develop one-half of one 

 horse power ; a twelve-foot mill three-fourths horse 

 power ; a fourteen-foot mill one horse power, and each 

 additional two feet in diameter of wheel develops practi- 

 cally one additional hor*se power up to a thirty-foot mill, 

 which develops eight horse power. The cost of the mill 

 ranges from forty dollars for the smallest size, up to 

 four hundred dollars for the largest. 



A five-inch pump geared to run forty-eight eight- 

 inch strokes a minute will discharge 1860 gallons of 

 water an hour; a six-inch pump geared in the same wav 

 will discharge 2760 gallons an hour, and an eight-inch 

 pump will discharge 4860 gallons an hour. A reservoir 

 one hundred feet square by four feet will contain 40,000 

 cubic feet, or about 300,000 gallons of water. A five- 

 inch pump discharging 1860 gallons an hour will in one- 

 third of a day, or eight hours, discharge 14,880 gallons. 

 In twenty days of eight hours each this is assuming 

 that the windmill runs one-third of the time 297,600 



