On the Constitution of mixed Gases, Sc. 545 
That moment we admit it every difficulty va- 
nishes, and every fact appears a simple and 
immediate consequence of it. The’ atmosphere, 
or to speak more properly the compound of 
atmospheres, may exist together in the most 
intimate mixture, without any regard to their 
specific gravities, and without any pressure upon 
one another. Oxygenous gas, azotic gas, hy- 
drogenous gas, carbonic acid gas, aqueous vapour» 
and probably several other elastic fluids may 
exist in company under any pressure and in any 
temperature, whilst each of them, however para- 
doxical it may appear, occupies the whole space 
allotted for them all. For, the space with them 
all-in it, is little more comparatively than a 
vacuum ; such is the great tcnuity of all clastic 
fluids, 
I shall now proceed to make a few observa- 
tions on that collected mas of elastic fluids con- 
stituting our atmosphere, the principal of which 
are the azotic atmosphere, the oxygenous atmos- 
phere, the aqueous vapour atmosphere, the car- 
bonic’ acid atmosphere and the hydrogencus at- 
mosphere. 
‘Before the modern discoveries in chemistry, 
the atmosphere was considered as one simple 
elastic fluid, sui generis, containing in it, by some 
meéaus or other, certain foreign substances not 
essentially but accidentally mixed with it. La- 
