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The distinguishing principle of that theory is, " that 
" mixed gases neither attract nor repel each other ; and that 
though existing together, every gas is as a vacuum to every 
" other gas." This has been confirmed by Mr. Henry, who, 
after a very scrupulous examination of the theory, under im- 
pressions very unfavourable, expresses himself satisfied, that 
" It is far better adapted than any former one, for explaining 
" the relation of mixed gases to each other, and espe- 
" cially the connexion between gases and water." 
As, however, it would be of no particular service to us, and 
as our limits will not allow us to give a view of the subject 
sutficiently comprehensive to be understood, we must refer 
you to Mr. Dalton's essays on the constitution of mixed 
aeriform fluids, &c. 
We would only remark that as every gas is as a vacuum to 
every other gas, and as Mr. Henry proved to the Royal 
Society, that the relation of gases to water is altogether 
a mechanical one, the quantity of gas absorbed by water 
being always exactly as the pressure ; it follows that the 
quantity of any of the atmospherical gases absorbed by water 
in contact with the atmosphere, will be proportional to the 
quantity or pressure of that particular gas ; and hence the sea, 
and indeed water of every description, when exposed, may 
perform the part of an equalizer, or regulator, if not a reno- 
vator of the atmosphere ; for should any of its constituent 
gases, by any means exceed its usual proportion, the pressure 
of that gas would be so much increased, and part would of 
course be absorbed by the water : at the same time, the pres- 
sure of the other gases collectively, must be as much dimin- 
ished, and consequently those gases must receive a portion 
from the water to restore the equilibrium. 
Hydrogen gas confined over water is as a vacuum to every 
other gas contained in that water, and the pressure by which 
those subaqueous gases are held, being removed, they quit 
the water, and assume their gaseous form in the vessel ; at 
