AIR PUMPS AND APPARATUS. 



191 



faces. In experiments requiring accurate exhaustion, care 

 should be taken that the receiver and various parts of the 

 pump be free from moisture, the vapor of which arising 

 would form an atmosphere, which would continue to rise as 

 long as any moisture remained. The operator should be pro- 

 vided with a number of receivers, of various kinds and sizes, 

 some open at top, having a brass plate with sliding rod ; 

 others with closed top, having a knob ; also a few glass jars, 

 for supporting fruit, &c. 



Price, $70, $75, and $85, according to style and finish. 



French Table Air Pump. (Fig. 178, as below.) This 



