AIR PUMPS AND APPARATUS. 221 



two plates, ground truly flat, and having pipes beneath, 

 communicating with each other by connecting tubes, and a 

 large pipe and cock below, which fits on to the table of the 

 air pump. If a glass receiver be placed over each trans- 

 ferer plate, they may be exhausted of air, and the lower 

 cock being turned, they may be removed from the air pump, 

 and set aside, that the continued result of the experiment, 

 whatever it may be, may be noted afterwards, and the air 

 pump in the interim used for other purposes. 



Price, large size, with two gallon receivers, $15.00. 



half " " $12.00. 



quart " $10.00. 



pint " $8.00. 



" single transferer plate, with stop-cock 



and stand, - $3.50 to $6.00 



Fig. 233. Fountain by Elasticity of Air.(Yig. 233.) 



A pneumatic apparatus, showing the elasticity 

 of the air. It is a glass vessel with a brass top, 

 and a tube within it, extending to near the 

 bottom of the glass. When this glass is partly 

 filled with water, and placed under a tall re- 

 ceiver of the air pump, the air being exhausted 

 by the action of the pump, the elasticity of that 

 air which remains within the vessel, drives the water through 

 the tube, and makes it play into the receiver like a fountain. 

 This action continues either until almost all the water is 

 driven out, or else until the air has become so rarefied that 

 it no longer has sufficient force to overcome the resistance. 



This apparatus should only be used with a transferer, as 

 the water is liable to be drawn into the air pump, and the 

 pump injured thereby. Price, $2.00. 



Water Hammer with Stop-cock. This apparatus (Fig. 234, 

 next page) consists of a glass tube about 2 feet long, closed 

 at one end, and the other having a brass cap and stop-cock, 

 to which may be connected a hose or flexible tube, commu- 

 nicating with the air pump. To use, the tube is half filled 

 with water and exhausted, when bubbles of air will be seen 

 to rise with great rapidity ; when completely exhausted 

 turn the cock and unscrew the hose. Now turn up and 

 down the tube, and the water will be found to descend with 

 a force like the stroke of a hammer. Price, $2.50. 



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