186 Mr. Dalton on the constitution of the atmosphere. 
According to one view. 
2. The altitude of each atmo- 
sphere differs from that of every 
other, and the proportions of 
each in the compound atmo- 
sphere gradually vary in the 
ascent. 
3. When two atmospheres are 
mixed, they take their places 
according to their specific gra- 
vity, not in separate strata, but 
intermixedly. There is however 
a separate stratum of the speci- 
fically lighter atmosphere at the 
summit over the other. 
According to the other view. 
2. The altitude of each atmo- 
sphere is the same, and the pro- 
portion of each in the compound 
atmosphere is the same at all 
elevations. 
3. When two atmospheres are 
mixed, they continue so, without 
the heavier manifesting any dis- 
position to separate and descend 
from the lighter. 
All that we have said hitherto has been relating to quiescent 
atmospheres, or such as are in a state of perfect equilibrium. 
How the case would be with regard to the earth’s atmo- 
sphere, such as it actually is, in a state of continual motion 
and agitation greater or less in all its parts, it is not very easy 
to ascertain ; and it is besides rather a question to be decided 
by experiment and observation than by any theory. I have 
a series of observations made on this subject ; but as they 
will require to be submitted in a considerable detail, I shall 
reserve them as a sequel to this essay on some future 
occasion.- 
