220 PROPERTIES OF AIR 



bottom, or side, of a vessel full of water, or any 

 other fluid, immersed in a medium rarer than 

 the fluid which the vessel contained ; whenever 

 this is the case, the fluid presses more than it is 

 resisted, the degree of pressure depending on 

 the degree of difference which exists between 

 the density of the fluid within, and the rarity 

 of the fluid without : hence we find that water 

 which existed in equilibrio in water without 

 weight, in air has weight ; pressing downwards 

 upon the air, more than it is resisted upwards 

 by the air. These effects flowing from the same 

 principle, are observable, when fluids of dif- 

 ferent densities are immersed together. When- 

 ever they do not chemically combine together, 

 they diffuse, and separate themselves into 

 different strata ; the denser falling, or sinking, 

 to the bottom ; and the rarer rising to the top, 

 in a regular and graduated manner. The 

 pressure, under these circumstances, is not 

 equal in every direction among the particles 

 of the whole mass ; the pressure downwards 

 is greater than the pressure upwards ; and a 

 vessel immersed in and balanced by the liquid, 

 would be carried down with it to the bottom of 

 the vessel. 



The errors, on this subject, which now pre- 

 vail, appear to me to arise from subjecting to 

 the same laws, solids and fluids together ; bo- 

 dies whose nature and properties are altogether 





