CHAPTER Xtt. 



GRAVITY AND LEVITY OF GASES, 



THE observations which I have made on the 

 state of equilibrium, and of weight of liquids, 

 equally apply with respect to the equilibrium 

 and the weight of gases also. If any given 

 quantity of gas of the same quality as that of 

 the surrounding medium, is received in a close 

 vessel, it will be found to subsist in a state 

 of equilibrium, or of balance. When the re- 

 ceiver of an air-pump is placed over the ba- 

 lance, having the bottle of air suspended from 

 the beam on one side, and which is counter- 

 balanced by a weight on the opposite scale ; if 

 the air is exhausted, as far as it is possible, out 

 of the receiver, the air confined in the bottle, 

 will be found gradually to preponderate, and to 

 be heavy. The weight which the air in the 

 bottle has acquired, or, more properly speak- 

 ing, the weight which has been generated, is 



