Note 212 — Chapter XII
Reading edition
Dr. Priestley appears to have been the first to observe the peculiar property of the diffusion of gases. Dr. Dalton, however, first drew attention to the important bearing of this fact on natural phenomena, and he published his views on The Miscibility of Gases in the Manchester Memoirs, vol. v. The following extract from his memoir On the Constitution of the Atmosphere will exhibit its bearings:—
It may be worth while to contrast this view of the constitution of the atmosphere with the only other one, as far as I know, that has been entertained.
According to one view, According to the other view,
1. The volumes of each gas found at the surface of the earth are proportional to the whole weights of the respective atmospheres. 1. The volume of each gas found at the surface of the earth, multiplied by its specific gravity, is proportional to the whole weight of the respective atmospheres.
Azote79 Azote76·6
Oxygen21 Oxygen23·4
Aqueous vapour1·33 Aqueous vapour0·83
Carbonic acid1·0 Carbonic acid0·15
——— ———
101·43 100·88
2. The altitude of each atmosphere differs from that of every other, and the proportions of each in the compound atmosphere gradually vary in the ascent. 2. The altitude of each atmosphere is the same, and the proportion of each in the compound atmosphere, is the same at all elevations.
3. When two atmospheres are mixed, they take their places according to their specific gravity, not in separate strata, but intermixedly. There is, however, a separate stratum of the specifically lighter atmosphere at the summit over the other. 3. When two atmospheres are mixed, they continue so without the heavier manifesting any disposition to separate and descend from the lighter.