MACHINERY 2Ji 



be single or double acting. In double-acting pumps the 

 water is discharged at each forward and backward stroke. 

 The capacity of a double-acting pump is twice that of a 

 single-acting pump. A direct-connected pump is on the 

 same shaft with the motor or engine, or coupled thereto. 



FIG. 193 A ROTARY PUMP 



386. Rotary pumps are used to some extent in pump- 

 ing about the farm. They are not suited for high lifts, 

 as there is too much slippage of the water past the 

 pistons. They are not very durable, and it is doubtful if 

 they will ever come into extensive use. 



387. Centrifugal pumps are used where a large quan- 



