43 o Nofuch Thing as SuSlion. [Book V* 



but the column E F, acting with its whole weight on 

 the quickfilver between F and D, caufcs it to prefs on 

 the air at D, and condenfe it. By increafing the 

 quantity of quickfilver the condenfation is increafed } 

 and it is found, that the {paces into which the air is 

 condenfed by different weights, bear a regular pro- 

 portion to thofe weights, and its denfity is confequently 

 increafed in proportion to the degree of prefTure exerted 

 upon it. 



It is, however, very probable, after all, that this 

 comprefllon has its limits, for we know of no body 

 which can be comprefled ad infinitum. 



From all that has been ftated, and particularly from 

 the experiment of Torricelli, it will be evident, that 

 the common notion of faction is a vulgar error ; and 

 that when a fluid rufhes fpontaneoufly into a given 

 fpace, it is in confequence of the air being expelled, or 

 made thinner in that fpace, than in that which is con- 

 tiguous to it, when the preflure of the atmofphere acts 

 upon the fluid, and forces it to occupy the fpace from 

 which the air is either entirely or partially expelled. 

 This is the principle on which the common pump is 

 conftructed ; for a vacuum being made in the tube by 

 the rifing of the pifton, the weight of the atmofphere 

 prefies upon the circumadjacent water, and forces it 

 up into the body of the pump : but this engine will 

 be more particularly defcribed in treating of hy- 

 draulics, r 



The elafticity of the air is now generally allowed to 

 depend upon the latent caloric or fire, which retains it 

 in its fluid form. If we take a bladder well clofed at 

 the neck, and containing but a fmall quantity of air; 

 while this bladder is expofed to the prefiure of the at- 

 mofphere it will remain in its primitive ftate, as when 

 the fmall quantity of air was admitted - t but if it is 

 i placed 



