AIR PUMPS AND APPARATUS. 



201 



In order that the contact with the plate of the pump may 

 be air tight, the bottoms of the receivers are ground perfectly 

 true. They are made of various shapes ; straight sides and 

 swelled, open top and with knob. 



Price, 4 in. $0.75; 5 in. $1.00; 6 in. $1.25. 



7 in. $1.50 ; 8 in. $1.75 ; 9 in. $2.00. 



10 in. $2.50; 12 in. $4.00. 



Low Receivers for the Air Pump. Fi =- 189 - 



(Fig. 189.) These receivers are used 

 where the articles placed under them do 

 not occupy much height, and consequent- 

 ly can be exhausted quicker than where 

 higher ones are used. 



Price, 5 in. $0.75 ; 6 in. $1.00. 

 7 in. $1.37; 8 in. $1.75. 



The Gallows Connector. (Fig. 190.) 

 This convenient apparatus is used in con- 

 nexion with the flexible tube, for con- 

 necting apparatus with the air pump that 

 otherwise could not so conveniently be at- 

 tached. The lower part of the ball has a 

 socket entering the gallows, which, by 

 loosening the screw over the ball, may be 

 readily disconnected. The connexions are 

 made with male screws ; a double female 

 connector is sometimes attached, where a 

 female screw is required. 



Hand Glass. This cut (Fig. 191) re- 

 presents a swelled glass receiver, about 

 5 inches in diameter, open at both ends, 

 and ground perfectly true and flat ; the 

 one end is about 4 inches in the aperture, 

 and the other two inches. Set the large- 

 end on the plate of the air-pump, and 

 place the hand on the small end, so as to 

 cover the glass ; then begin to exhaust, 

 and you will feel the pressure of the air ; for the air being 

 taken from under your hand out of the glass, the external 

 air will press your hand to the glass, so that you can scarce 

 move it. Upon letting in the air it will be loosened again. 



Price, $1.50. 



Fig. 191. 



