PUMPING WATERS. 69 



At A is attached the supply pipe called the drive 

 pipe, 10 to 20 ft. long. The bell F contains air to act 

 as a cushion. There is a valve B, having a weight 

 keeping the valve open normally. Suppose water 

 starts to flow out of this valve it acquires velocity, 

 increasing too so much as to overcome the Weight 

 and close the valve. Rushing onward, it gains con- 

 siderable pressure, so much so that the ball valve 

 lifts and the water flows up the supply pipe. Now 

 the valve B falls again and the process is repeated. 

 The action of the hydraulic ram illustrates the con- 

 version of potential energy into kinetic energy, 

 kinetic into pressure, and pressure, again, to potential 

 (vide hydraulics). Now, referring to the line dia- 

 gram, fig. 52, we have H = delivery head and h = 

 supply head ; then the efficiency of the apparatus 



= ;/= ri2 - o'2A/Y . . (22) 



The quantity of water which will run to waste by 

 way of the dash valve B, 



<3> 



n being as in equation 22. 



The actual water delivered per stroke 



The correct diameter of the drive pipe 



. . . (25) 



The correct diameter of the supply pipe 



-rf-5. . ; . (26) 



