108 SMALL WATER SUPPLIES. 



compression pressure was obtained with this pump 

 than with the simple pump, and consequently higher 

 efficiencies with the same lift. 



The author then dealt with two-barrel and suction- 

 lift pumps and high-lift pumps. He pointed out how 

 any Humphrey pump could be converted into a high- 

 lift pump by means of an air vessel fitted with valves 

 and called an intensifier. Into this vessel air is drawn 

 into and rejected at each cycle. Fig. Sic will help to 

 make the operation of such a pump clear. A and B 

 are the barrels of a two-barrel pump, and at the end 

 of the splay pipe D there are two air vessels E and F, 

 the latter being large enough to give a continuous 

 flow at outlet O, and to maintain a practically uni- 

 form pressure. The smaller air vessel E is fitted with 

 a downwardly projecting pipe K, open to the atmos- 

 phere at the top and carrying a valve L at its lower 

 extremity arranged to close under the action of the 

 rising water. The cycle starts with an explosion, 

 all valves except L being shut and the water level, 

 as shown. While the water level in E is rising to 

 L, air is merely being discharged into the atmosphere, 

 and, as no work is being done by the column of 

 water, it gains speed until valve L is shut by impact. 

 Imprisoned in E there is now a definite quantity 

 of air, which suffers compression until its pressure 

 reaches that at which the high-pressure water valves 

 W can open and allow the remaining kinetic energy 

 of the column to force water into F. Valves W 

 close when the column comes to rest, but there re- 

 mains enough energy in the compressed air in E to 

 give, by expansion, the return flow, which causes 

 exhaust in A and compression of the fresh charge in 



