Dt)CTRINE OF MIXED GASES. 57 



ous compounds. The origin of this equilibrium is eafily col- 

 leded from the preceding theory and the laws of pneumatics. 

 For the globules of carbonic acid, contained in the gafeous 

 compound, invariably exert the force of 30 mches of mercury; 

 they thenpfore prove too powerful for the rarefied gas of the 

 wafer, which they compref<, and infinuate part of their own 

 fubftances into the fluid. Whilft this operation is going on at 

 innumerable points in the furface, portions of the fame gas 

 are conftantiy forced through the companments of eafy trant. 

 miiCon, by the flighteft agiiations. Now the quantity of gas 

 which is difcharged into the air of the jar, is greateft at firft, 

 and continually dimini flies ; on the contrary, the quantity that 

 is forced into the water through the former paflat^es, is leaft at 

 firfl, and increafes afterwards ; confequently the two quantities 

 ultimately become equal, and eftablifti the equilibrium in quet- 

 tion, by the contrariety of their effeds. 



The preceding is a general propofition, which explains a Concluding «• 

 variety of appearances, fuch as Mr. Henry has defcribed, by "^"^ 

 by the well known principles of mechanics. Should the con- 

 fideration of it be attended with conviction on his part, he 

 perhaps will give a new turn to his experimental enquiries, 

 and endeavour to difcover the law of affinity, which coane6ls 

 water with the different gafes. It is almoft certain, that this 

 law is not the fame in all cafes, as will be feen by comparing 

 the experiments of M. la Saufl'ure on the folution of water in 

 common air, with Mr. Kirwan's obfervations on the folvent 

 powers of hidrogen ; which may be found at page 14 of the 

 lirft edition of his EflTay on Phlogifton, 



JOHN GOUGH. 



Middlejkaw, Aug, 23, 1804.. 



P. S. The following error requires corre6lion : In Vol. VIII. 

 page 244, line 21, before the words, as oft as uater, read 

 therefore, and ftrike out the fame conjunction in line 22. 



An 



