292 PRESSURE IN THE AIR y 



other from within. In like manner, the re- 

 ceiver of the air-pump will be immoveably 

 fixed to the pump-plate ; the bladder with 

 with which the cylinder may have been co- 

 vered, will burst, as soon as the air within is 

 exhausted; mercury will be forced up an ex- 

 hausted tube to the elevation of 29 or 30 

 inches, and water as high as 34 or 35 feet. 



Although the effects which I have above 

 enumerated, and a multitude of others of the 

 same kind, evidently appear to me to be caused 

 by the expansible force of the air without, in 

 consequence of diminished resistance from a 

 high state of rarefaction within, and in which 

 the supposed weight of the atmosphere has no 

 concern ; I must be permitted to express my 

 surprise, that these phenomena, on the con- 

 trary, are referred (by experimental philoso- 

 phers in general,) to the force of the incum- 

 bent weight of the air, and not to its expansi- 

 bility. 



In order to decide the point with as much 

 accuracy as the subject will admit, and to 

 prove that it is not caused by the gravity or 

 weight of the atmosphere, I subjected them 

 to the test of experiments, in themselves so 

 simple, but, at the same time, so satisfac- 

 tory, that I flatter myself they will cause 

 the same conviction in others, as they have 



