E. W. Morley — Self- Acting Mercurial Air pump. 441 



Fig. 1 shows a perspective view of the air compressor, a is 

 a copper cylinder : it contains a caoutchouc gas bag which is 

 fastened to a brass tube ending in three stopcocks seen just 

 beneath the cylinder. To two of these are secured tubes 

 which lead to two Toepler pumps : d is one of these tubes. 



The pulley e is attached to the key of a common three-way 

 stopcock. In the position shown, water is admitted to the 

 cylinder; if the pulley and stopcock were turned one-quarter 

 revolution towards the right, the escape would be opened. 



The force for turning the pulley is supplied by the weight 

 of mercury in one or the other of the small glass globes b and 

 c. These are suspended from the pulley by a wire cord : they 

 are connected beneath by the flexible tube/. The top of c is 

 connected by a flexible tube i to a glass tube closed at I, and 

 open above. The top of b is connected by a flexible tube g to 

 the tube h and thus to the air in the gas bag in a. 



The three way stopcock is shown at the instant of opening 

 the admission of water to a. The' air in the gas bag is there- 

 fore at the pressure of the atmosphere, and the mercury stands 

 at the same level in b and in the tube/'. As the air in a is 

 compressed, and as the air in the connected Toepler pump is 

 raised, the mercury in b is also driven into c, and at length 

 fills c and rises into the tubes i and I ; c thus becomes heavy 

 enough to turn the pulley and stopcock unless prevented. 

 When it is permitted to turn it by descending nearly to the 

 level to which b rises, water escapes from the cylinder. The 

 air in the gas bag expands, permitting not only the descent of 

 the mercury in the Toepler pump, but also of the mercury 

 from c to I). The latter then becomes heavy enough to turn 

 the pulley into its present position ; and so the process may be 

 indefinitely repeated. 



The release of the pulley when in its present position is 

 controlled electrically. At m is a radial arm turning with the 

 pulley and stopcock. It is prevented from turning to the 

 right by the armature of an electro-magnet. The circuit 

 through the coils of this magnet is completed through the 

 mercury of the Toepler pump when this finishes its stroke and 

 discharges itself of air. Some little time before this instant, 

 the loading of c is completed : accordingly, at the instant of 

 the discharge and the consequent completion of the circuit, 

 the three-way stopcock turns quickly to the right, water 

 escapes from «, the air pressure is relieved, and the mercury 

 descends in the Toepler, and also in the globes b and c. 



It is important that the next ascent of mercury should not 

 begin too soon, but that time should be given for air to flow 

 into the vacuous body of the pump. This is managed by re- 

 tarding the flow of mercury from c back into b : they are 



