HISTOKY OF THE ATOMIC THEOBY. 47 



removal of that pressure, are mechanically mixed with the 

 liquid, and not chemically combined with it." 



He had already mentioned Dr. Henry's discovery, that 

 the quantity of gas absorbed is as the density or pressure. 



** 2. Gases so mixed with water, &c., retain their elasticity 

 or repulsive power amongst their own particles, just the same 

 in the water as out of it, the intervening water having no 

 other influence in this respect than a mere vacuum." 



"3. Each gas is retained in water by the pressure of gas of 

 its own kind incumbent on its surface abstractedly considered, 

 no other gas with which it may be mixed having any per- 

 manent influence in this respect." 



" 4. When water has absorbed its bulk of carbonic acid gas, 

 &c., the gas does not press on the water at all, but presses 

 on the containing vessel just as if no water were in. When 

 water has absorbed its proper quantity of oxygenous gas, 

 &c., that is, l-27th of its bulk, the exterior gas presses on 

 the surface of the water with 26-27 ths of its force, and on 

 the internal gas with l-27th of its force, which force presses 

 upon the containing vessel, and not on the water. With azotic 

 and hydrogenous gas the proportions are 63-64ths and l-64th 

 respectively. When water contains no gas, its surface must 

 support the whole pressure of any gas admitted to it, till the 

 gas has in part forced its way into the water." 



"5. A particle of gas pressing on the surface of water is 

 analogous to a single shot pressing upon the summit of a 

 square pile of them. As the shot distributes its pressure 

 equally amongst all the individuals forming the lowest 

 stratum of the pile, so the particle of gas distributes its 

 pressure equally amongst every successive horizontal stratum 

 of particles of water downwards, till it reaches the sphere 

 of influence of another particle of gas. For instance, let 

 any gas press with a given force on the surface of water, 

 and let the distance of the particles of gas from each other 

 be to those of water as 10 to 1, then each particle of 



