THE WATER-EAiAr. 



227 



Its power depends on the momentum of the stream. 

 Its principal parts are the reservoir, or air-chamber. A, 

 (fig. 255), the supply pipe, B, and the discharge pipe, C. 

 The running stream rushes down the drive, or supply- 

 pipe, J^, and, striking the waste valve, J?, closes it. The 

 stream being thus suddenly checked, its momentum opens 

 the valve, ^, upward, and drives the water into the reser- 

 voir, A, until the air within, being compressed into a 

 smaller space by its elasticity, bears down upon the water, 

 and again closes the valve, J. The w^ater in the supi^ly- 



Fig. 255. 



pipe, ^, has, by this 

 time, expended its mo- 

 mentum, and stopped 

 running ; therefore the 

 valve, J), drops open 

 again, and permits it to 

 escape. It recommences 

 running, until its force 



again closes the waste 



valve, D, and a second water-ram. 



portion of water is driven into the reservoir as be- 

 fore, and so it repeatedly continues. The great force of 

 the compressed air in the reservoir drives the water up 

 the discharge-pipe, C, to any required height or distance. 



The mere weight of the water will only cause it to rise 

 as high as the fountain head ; but like the momentum of 

 a hammer, which drives a nail into a solid beam, which a 

 hundred pounds would not do by pressure, the striking 

 force of the stream exerts great power. 



The discharge pipe, C, is usually half an inch in diame- 

 ter, and the supply-pipe should not be less than an inch 

 and a fourth. A fall of three or four feet in the stream, 

 with not less than half a gallon of water per minute, with 

 a supply-pipe forty feet long, will elevate water to a 

 height as great 



as the streno-th of common half-inch lead 



