Description of an Air Pump. 



87 



it is another aperture communicating with the tube G ; and the 

 part EC is constructed in such a manner, that when E is upAvard, 

 a passage is opened between the aperture F and tube A, and also 

 between the tubes B and G. If the pump be now worked, it is 

 evident the air will pass in at F and out at G, that is, it exhausts 

 at F and condenses at G. If, however, we give EC a quarter of 

 a revolution, and bring C upward, the passages from A to F, and 

 from B to G, are closed, and others opened from B to F, and from 

 A to G ; and by working the pump the air will now be made to 

 pass in at G, and out at F, or in the reverse direction from that 

 just described. This pump, therefore, like the one described by 

 Dr. Hare, when worked is constantly exhausting and condensing. 



The uses to which this air pump may be applied, obviously 

 include all those of a common air pump and condenser ; and 

 also enables the operator to transfer any gas that will not corrode 

 the metals from one vessel to another, (as does that of Dr. Hare.) 

 To do this, it is only necessary to attach tubes at F and G lead- 



