IDG 



BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE. 



Fi s- 182 - truly ground, having in the 



centre a screw to fit the stop- 

 cocks of the usual apparatus 

 accompanying these instru- 

 ments, and beneath a pipe 

 connecting with the brass 

 base of the barrel of the 

 pump, having a valve open- 

 ing upwards, there being one 

 also in the piston opening 

 the same way ; the action is 

 the same as described in the 

 large double barrel air pump. 

 Suppose the receiver to be 

 placed on the plate, care being taken that it is free from 

 dust and grit, and a small quantity of oil rubbed thereon, 

 draw the handle up, and a vacuum will be formed under- 

 neath the piston. The air then in the receiver will, by its 

 elasticity, force against the valve at the bottom of the barrel, 

 and rush up to fill the vacant space. When the piston is 

 forced down again, it compresses the air beneath it, which 

 closes the valve at bottom, and at the same time opens the 

 valve which is in the piston itself, and the compressed air 

 thereby escapes ; thus a quantity of air equal to the capacity 

 of the barrel is got rid of a second lift will withdraw a 

 second portion, and so the operation may be continued at 

 pleasure. Price, small size, with receiver, $7.00. 



Fi 183 " medium size > $9.00. 



This cut (Fig. 183) 

 represents a larger 

 size single barrel 

 air pump and re- 

 ceiver, having in 

 the drawing the 

 barrel cut away, 

 to show the piston 

 and valves ; the 

 construction is the 

 same as the one 

 above described. 

 Price, with re- 

 ceiver, $12. 



