i8s Mr. Dalton on the constitution of the atmosphere. 
permanent ? Would a mixed atmosphere, which in fact as a 
whole, consisted of equal weights of carbonic acid and hydro- 
gen, continue to exhibit at the surface of the earth equal 
volumes only in mixture ? Or, on the other hand, would not 
the whole be wrought up in due time into one uniform com- 
position in all its extent, of 20 volumes of hydrogen with one 
of carbonic acid, as many suppose to be the nature of the 
earth’s atmosphere with regard to its component parts ? 
Before these questions are discussed we shall put the case 
in a different form : suppose a mixture of 20 volumes of 
hydrogen and one volume of carbonic acid (that is equal 
weights of each ) , were put into a large reservoir under the 
constant pressure of 30 inches of mercury, and from this 
reservoir were passed by means of a stop-cock into the inde- 
finite perpendicular tube. A, perfectly void, till such time as 
the equilibrium between the reservoir and the tube was 
established : query, what would be the final arrangement of 
the two gases in the tube ? I believe it will be allowed by 
all, that the final arrangement of the mixture of gases will 
be precisely the same in this case as in the one previously 
stated, whatever that arrangement may be. 
Now I apprehend it is demonstrable, from what we know 
of the nature of mixed gases, that each of the two gases 
would be disposed just the same as if the other was not 
present. They would be mixed in equal volumes at the 
earth’s surface ; the carbonic acid would rapidly diminish in 
density in ascending, and terminate perhaps at 28 or 30 miles 
of elevation ; the hydrogen would slowly diminish in den- 
sity, and terminate perhaps at 11 or 12 hundred miles of 
elevation. 
