270 



SCIENCE PROGRESS 



outlet o and to maintain a practically uniform pressure. 

 The smaller air vessel e is fitted with a downwardly pro- 

 jecting pipe k, open to the atmosphere at the top and carrying 

 a valve l at its lower extremity arranged so that it closes under 

 the action of rising water. The cycle starts with 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 



M IV I ■ ■■ m i ■ — rw — - 



ip w 



■ — 1 



Fig. 6. 



to rest but there remains enough energy in the compressed 

 air in e to give, by expansion, the return flow, which causes 

 exhaustion in a and compression of the fresh charge in b to 

 start a fresh cycle. When the water level falls below valve 

 l, this valve opens and air is admitted into e for the rest of 

 the return stroke. 



Now it is easy to see that if the pipe k is made vertically 

 adjustable with regard to e, the point of the cycle at which 

 l shuts can be varied and more or less air entrapped in e 

 at will. But the amount of energy stored in this air will 

 also vary with its quantity, for we assume that the degree 

 of compression remains constant and is indeed fixed by the 

 pressure maintained in f. Consequently the ratio of the total 

 energy of the working stroke to the energy stored in the 

 compressed air in e can be made anything desired ; in 

 other words we can obtain any compression pressure of 

 the new charge in b which we like and this independently 



