Mr. Dalton on the constitution of the atmosphere. 183 
The arguments in support of this notion may be derived 
from the following facts : 
1st. When two gases, not having a manifest chemical 
action upon each other, are put into a vessel of small limited 
capacity, they are found in a short time to be uniformly 
diffused through the capacity of the vessel, whatever be their 
proportions. 
2d. Let a bottle, having its air exhausted, be half filled 
with water, and the other half with a mixture of equal 
volumes of two gases, suppose hydrogen and carbonic acid ; 
then let an air-tight stopper be applied, and the contents of 
the bottle be duly agitated. The carbonic acid will be found 
equally diffused through the whole capacity of the bottle, the 
same in the water as out of it ; but the hydrogen in the 
water will only be — or of the density of that above 
the water. In this case each gas will be arranged, both 
within and without the water, precisely the same as if it was 
the only gas present. And if a third gas could afterwards 
be introduced into the bottle in like manner, it would take 
its place in and out of the water independently of the other 
two ; and so on with any number. No pressure of any one 
gas on the surface of the water can confine another gas in 
the water ; it must be a pressure arising from the same gas. 
3d. If a portion of ether, alcohol, &c. be put into a bottle, 
and it be close corked, the vapour will ascend and fill the 
bottle, whatever air be present ; its quantity and force will 
be the same whether there be any air, or none, being entirely 
regulated by the temperature. 
From these three facts, but more especially from the two 
last, it appears to me as completely demonstrated as any 
