374 IRRIGATION FARMING. 



of these vacuum-pumps, and would rather place de- 

 pendence upon the duplex compound pumps with 

 condensers. In these pumps the steam works ex- 

 pansively, first in the high-pressure cylinders, and 

 then, by exhaust, into the opposite low-pressure 

 cylinders, the high and low pressure cylinders be- 

 ing tandem on the cylinder, and the condensers re- 

 turning hot water to the boiler and saving valuable 

 fuel. 



Centrifugals. — These pumps are worked by sta- 

 tionary engines and are quite generally used by sewer 



contradlors. They are 

 good for low lifts, and 

 will throw sand and 

 gravel readily. On a 

 twenty-foot lift a No. 

 i^ Van Wie pump 

 will irrigate ten acres 

 of land and require a 

 two horse-power en- 

 gine. A No. 2 pump 



PIG. 85-CENTR.FUGAL PUMP. ^;^ ^^^^j^ ^^^^^^ 



acres, requiring three horse-power. No. 3 pump, forty 

 acres, with six horse-power engine. No. 4 pump, 

 eighty acres, with ten horse-power engine. No. 6 

 pump, 160 acres, with twenty horse-power engine. 

 No. 8 pump, 320 acres, with forty horse-power engine. 

 The writer once saw an ordinary ten horse-power 

 threshing engine drive a No. 8 pump, raising water 

 enough — 4,500 gallons a minute — to irrigate 320 acres 

 of land easily. The exterior view of a centrifugal 

 pump is shown in Fig. 85. 



