274 



SCIENCE PROGRESS 



valves i and r remain locked. Now the column begins to return, 

 owing to the expansion of the compressed cushion in c and 

 this causes exhaust and cushion in a ; at the same time there is a 

 fall of pressure in c to atmosphere, then valve/is opened against 

 a light spring and a fresh supply of air enters. 



So far we have had one outward and one return stroke but 

 the expansion of the cushion in a starts a second out-stroke 

 which results in drawing in a new combustible charge into a 

 through valves i and r, which were released on the shutting of 

 the exhaust valve e. As the second out-stroke is nearly as long 

 as the first, it follows that too much combustible mixture is 

 drawn in ; the surplus is got rid of on the second return 

 stroke by allowing it to escape into the receiver x and to 

 raise the pressure slightly therein. Valve i was shut by its 

 spring but r waits to be shut by the action of the water ; 

 when this occurs chamber a contains a definite volume of com- 

 bustible mixture, the size of charge being fixed by the height 

 of r. Finally, we have only to observe that the second out- 

 stroke towards c merely compressed the air in c without causing 

 delivery to take place but storing in the air the energy given 

 out by the expansion of the cushion in a. The air in c now 

 expanding gives the compression stroke in a and the combustible 

 charge is ready to be ignited to start the next cycle. 



Perhaps the whole cycle, which may take two seconds to 

 accomplish, sounds a little complicated but if so it is merely 

 because of the length of the description. It may be easier to 

 grasp the action if it is set out to show the simultaneous steps 

 in a and c, thus : 



ist Out-stroke 



1st In-stroke 



2nd Out-stroke 



2nd In-stroke 



Expansion to atmosphere, 

 take of scavenging air. 



In- 



Exhaust till water shuts valve e. 

 Cushion till water comes to 

 rest. 



Expansion of cushion to atmo- 

 sphere. Intake of com- 

 bustible charge in excess. 



Rejection of surplus charge till 

 water shuts valve r. Com- 

 pression of charge till water 

 comes to rest. 



Expulsion of air till water shuts 

 valve s. Compression and dis- 

 charge of compressed air till 

 water shuts valve g. Cushion 

 till water comes to rest. 



Expansion of cushion to atmo- 

 sphere. Intake of fresh air. 



Compression of air but not 

 sufficient for further delivery. 



Expansion of compressed air. 



