AIR PUMPS AND APPARATUS. 



205 



Fig. 231 



Fig. 2 '2. 



The Fountain in Vacua. (Fig. 200, as above.) The 

 fountain consists of a tall receiver, of glass, about five inches 

 wide in the swell, but contracted at the top, and cemented 

 by a neck at the lower end to a brass cap, having within a 

 jet pipe attached to a stop-cock, which screws into the cap ; 

 the whole is mounted on a stand when not in use. To use, 

 the fountain is connected with the air pump by means of 

 the stop-cock and tube ; after the air is exhausted out of the 

 receiver, the cock is shut to prevent its return ; then the 

 whole is unscrewed from the plate of the receiver, and the 

 lower end of the tube is immersed in a vessel of water ; on 

 opening the stop-cock, the pressure of the atmosphere on 

 the surface of the water in the vessel having no counterpoise 

 from the interior of the cylinder, forces up the fluid through 

 the jet-pipe with considerable velocity, which forms a pleas- 

 ing jet-d'eau, or fountain in vacuo. 



Price, $4.50 ; larger, $5.00. 



