HI8T0BY OF THE ATOMIC THEORY. 45 



own experiments justified a different opinion. Dalton took 

 the subject up at this stage, and says the result "estab- 

 lishes this remarkable fact, that a lighter elastic fluid cannot 

 rest upon a heavier, as is the case with liquids ; but they are 

 constantly active in diffusing themselves through each other 

 until an equal equilibrium is effected ; and that without any 

 regard to their specific gravity, except so far as it accelerates 

 or retards the effect according to circumstances." * 



** The only apparatus found necessary, was a few phials 

 and tubes with perforated corks ; the tube mostly used was 

 one 1 inches long, and of l-20th inch bore ; in some cases a 

 tube of 30 inches in length, and l-3rd inch bore was used; 

 the phials held the gases that were subjects of experiment, 

 and the tube formed the connection." p. 261. This tube 

 was often a piece of tobacco pipe. 



He believes that this proves his theory of elastic fluids to be 

 correct, that gases are as a vacuum to each other, and it no 

 doubt does favour it, especially as he added that they might 

 be obstructed as a stream of water by a stony bed. Still this 

 very explanation takes away much of the original meaning, 

 and any of his difficulties as to the mutual action of gases 

 must be cleared by further experiments, as has been the case 

 with the laws of diffusion which have already been shewn to us 

 by Professor Graham. There is no doubt that Dalton's 

 expression is an useful attempt to grasp a great difficulty, not 

 yet grasped, we shall see him returning to it again in the 

 next paper. 



On October 2 1st, 1803, he read to the Literary and 

 Philosophical Society, another investigation " On the ab- 

 sorption of gases by water and other liquids." p. 27 1 ., Vol. I., 

 New Series. 



In this he says, 2. " If a quantity of water freed from 

 air be agitated in any kind of gas not chemically uniting 

 with water, it will absorb its bulk of the gas, or otherwise a 



• Page 260, Vol. I., New Series. 



