304 PRESSURE IN THE AIR,. 



had upon this subject with men of science, I 

 have been much amused with the various argu- 

 ments they have employed, and with the diffe- 

 rent false facts which they have advanced, in 

 order to invalidate the force of these experi- 

 ments. Tt was said by one, that instead of 

 employing a bladder of the same size as the 

 receiver, a glass globe ought to have been 

 used ; and in that case, on letting in the air 

 from the globe into the receiver, the mercury,, 

 instead of rising to 29 inches, would only have 

 risen to half that height. Nothing can be more- 

 certain, and the reason is most obvious ; in- 

 stead of the air which was contained in the 

 globe being altogether transmitted from it into 

 the receiver only, as it is from the bladder, the 

 air would fill the globe and the receiver together; 

 and in consequence of the increased dilatation 

 which the two cubic feet of air underwent, by 

 occupying the spajce of four feet, contained by 

 the globe and the receiver together, instead of 

 two, the expansible force of the air must be 

 diminished in proportion, and the mercury, in- 

 stead of being forced up to 29 inches, would 

 only rise to 14^. A second very judiciously 

 observed, at the time I was making some expe- 

 riments on the subject, that I only exhausted a 

 given quantity of air out of the receiver, which 

 sunk the mercury to the same level as the mer- 

 cury in the basin, and merely restored the same 



