548 Farm Mechanics. 



694. Rate of Pumping. The rate of discharge from a 

 common single acting suction pump is determined by the 

 area of effective cross-section of the cylinder, the length 

 of the stroke and the number of strokes per minute. 

 Taking a 2.5-inch cylinder, which would have an effect- 

 ive cross-section of about 4.7 square inches and supposing 

 it to make a 5-inch stroke at the rate of 30 per minute, 

 the amount of water pumped per hour would b0 



4.7X5X30X60 



23i ~ 183.1 gallons. 



or enough for about 21 cows allowing 72 pounds per head. 



695. Relation of Size of Suction and Discharge Pipe and 

 Piston to Power Required to Work the Pump. When a 

 large piston is worked on a small suction and discharge 

 pipe it is necessary for the water to travel much faster 

 through these than when they have an effective diameter 

 equal to that of the piston ; but to increase the velocity of 

 flow through a pipe requires an increase of pressure so that 

 more power is required to pump the same quantity of 

 water through a 1-inch pipe, using a 3-inch cylinder, than 

 to pump the same amount in the same time through a 

 3-inch pipe. In the apparatus represented in Fig. 259, 

 when the pump with the 3-inch cylinder C is worked, dis- 

 charging water through the 3-inch discharge pipe 3, lifting 

 the water to a hight of about 18 feet and working the 

 pump at the ordinary rate, the pressure gage E shows 

 that the pumping is developing a pressure of about 9 

 pounds to the square inch. If now the pump is kept work- 

 ing at the same rate and the gate valve in 3 closed, while 

 that in the 2-inch pipe is opened, the pressure is seen to 

 rise to nearly 11 pounds per square inch. Then on open- 

 ing the gate valve in the 1-inch pipe and closing that in the 

 2-inch the pressure rises to between 13 and 14 pounds, but 

 when closing the 1-inch gate and opening that in the I - 

 inch pipe the gage registers a pressure of between 18 and 

 19 pounds per square inch of the piston, when the same 



