246 GRAVITY AND LEVITY 



which is opposed to them, by the surrounding 

 medium. The same effects take place when 

 fluids of different degrees of density, are mixed 

 and diffused together ; the denser fluid will 

 sink ; the rarer will rise. Although fluids, with 

 relation to each other, subsist in a state of 

 equilibrium, they, nevertheless, have weight, 

 when they are placed in media of greater rarity 

 than themselves ; the question is riot, whether a 

 bucket of water has weight in air, but whether 

 any solid substance, when placed at the bottom 

 of it, would be more pressed upon, than it 

 would be, if it were placed near the upper sur- 

 face. The experiment wjiich proves the ques- 

 tion, is decisive in itself. 



If a glass tube, of an inch in diameter, is filled 

 with water, and a piston immersed in it, which 

 is suspended from the arm of a balance ; the 

 same weight, in the opposite scale, will balance 

 the piston, in whatever part of the column of 

 the fluid the piston is immersed ; and if the 

 same piston, balanced in the same way, be im- 

 mersed in any part of a volume of water of any 

 breadth, or depth, however great these may be, 

 the additional quantity of water in which the 

 piston is immersed, will not add one particle 

 to its weight ; the measure of one ounce, 

 which kept the piston suspended in the 

 tube, of oue inch bore, at the depth of one 

 foot, will not have that weight increased, 



