112 FARM MECHANICS 



and forced into an overhead tank. Jacks are manufac- 

 tured which bolt directly to the pump, and there are 

 pumps and jacks built together. A pump jack should 

 have good, solid gearing to reduce the speed. Spur- 

 gearing is the most satisfactory. Bevel-gears are waste- 

 ful of power when worked under heavy loads. Power 

 to drive a pump jack is applied to a pulley at least 

 twelve inches in diameter with a four-inch face when 

 belting is used. If a rope power conveyor is -used, 

 then pulleys of larger diameters are required to con- 

 vey the same amount of power. 



Only general terms may be used in describing the 

 farm pump, because the conditions differ in each case. 

 Generally speaking, farmers fail to appreciate the 

 amount of power used, and they are more than likely 

 to buy a jack that is too light. Light machinery may 

 do the work, but it goes to pieces quicker, while a heavy 

 jack with solid connections will operate the pump year 

 in and year out without making trouble. For in- 

 creasing or reducing either speed or power some kind 

 of jack is needed. All farm machines have their best 

 speed. A certain number of revolutions per minute 

 will accomplish more and do better work than any 

 other speed. To apply power to advantage speed jacks 

 have been invented to adjust the inaccuracies between 

 driver and driven. 



IRRIGATION BY PUMPING 



The annual rainfall in the United States varies in 

 different parts of the country from a few inches to a 

 few feet. Under natural conditions some soils get too 

 much moisture and some too little. Irrigation is em- 

 ployed to supply the deficiency and drainage, either 



