286 



EXPERIMENTS WITH THE AIR-PUMP 





If the flask used for showing the effect of atmospht 

 pressure, art. 27, p. 246, be placed under the receiver 

 of the air-pump, a jet will issue from it when the pump 

 is worked, for the pressure of the air upon the water 

 inside the flask is greater than the pressure outside. 



The increase of a volume of air caused by decrease 

 of pressure may be demonstrated in various ways by 

 means of an air-pump. A Cartesian diver, made so 

 heavy as to sink, will rise if the vessel which contains 

 it is placed under the receiver, and the air withdrawn. 

 A bladder, only partially filled with air and closed, 

 distends under the receiver of an air-pump; so does a 



shrivelled apple, because it 

 contains air in the interior. 

 Dense soapsud, placed at the 

 bottom of a tumbler, in a 

 layer about l cm high, fills the 

 tumbler to the edge, when 

 the air in the receiver is rare- 

 fied. A test-tube, nearly 

 filled with water, and in- 

 verted in water, as shown ir 

 placed undei 



the receiver, will become nearly empty when the pumj 

 is worked, because the air in the .test-tube expands 

 when air is again admitted into the receiver, the 

 liquid rises in the test-tube to its former height. Ar| 

 egg, through the more pointed end of which a fin(; 

 aperture is made, will empty itself, if it is placed wifl 1 

 the perforated end upon a small tripod made of wire 

 under the receiver; the reason is that the egg contains 

 a quantity 'of air enclosed at the wider end, whicl 



