AND EXTERNAL RESISTANCE, 



295 



bladder, with which an exhausted receiver is 

 covered, is not caused by weight or the per* 

 pendicular pressure downwards of gravitating 

 or ponderable air, is proved by the bladder 

 bursting with as much facility if it be exposed 

 to the lateral, as to the perpendicular pressure, 

 upwards as downwards. To decide the point, 

 however with the utmost accuracy, I placed a 

 small cylinder, hav- 

 ing a bladder close- 

 ly tied over its top, 

 upon an exhausting 

 pump ; and over the 

 cylinder thus cap- 

 ped, a receiver ; so 

 that there were be- 

 tween the receiver 

 and the cylinder, 

 six cubic inches of 

 atmospherical air, 

 weighing about 10 grains, from which the exter- 

 nal air was entirely excluded. On exhausting 

 the air out of the cylinder, the bladder with 

 which it was covered, burst with as much faci- 

 lity by the force of those 10 grains of air, as 

 it does when exposed to the influence of the 

 whole weight which it is supposed the column 

 of atmosphere exerts on the surface. If weight 

 .therefore, be the cause, of which the bursting- 



