FOOTNOTES:
[212] 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 theearth are proportional to the whole weights of the respective atmospheres. | 1. The volume of each gas found at the surface of the earth, multiplied byits specific gravity, is proportional to the whole weight of the respective atmospheres. | ||
| Azote | 79 | Azote | 76·6 |
| Oxygen | 21 | Oxygen | 23·4 |
| Aqueous vapour | 1·33 | Aqueous vapour | 0·83 |
| Carbonic acid | 1·0 | Carbonic acid | 0·15 |
| ——— | ——— | ||
| 101·43 | 100·88 | ||
| 2. The altitude of each atmosphere differs from thatof 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, andthe proportion of each in the compound atmosphere, is the same at all elevations. | ||
| 3. When two atmospheres are mixed, they take their placesaccording to their specific gravity, not in separate strata, but intermixedly. There is, however, a separatestratum of the specifically lighter atmosphere at the summit over the other. | 3. When two atmospheres are mixed, they continueso without the heavier manifesting any disposition to separate and descend from the lighter. | ||
[213] The discussion of this question, commenced by Arago in his Eloge, was continued by Lord Brougham in his Lives of Watt and Cavendish, and by Mr. Vernon Harcourt, in his address as President of the British Association, and more recently in his Letter to Lord Brougham. Watt’s Letters on the subject have been since published under the superintendence of Mr. Muirhead.
[214] See several papers On Ozone, by Professor Schönbein, in the Philosophical Magazine, and in the Reports of the British Association. Consult a paper by the Author: Athenæum, September, 1849.
[215] Memoire sur l’Ozone; Bàle 1849. Poggendorff’s Annalen, lxxvii., p. 592. Ibid, lxxviii. p. 162.
[216] Chemical Gazette, 1849.
[217] Iodide of silver has been found at Albarradon, near Mazapil, in Mexico. Iodide of mercury, of a fine lemon-yellow colour, has been discovered in the sandstone of Casas, Viegas, Mexico. Algers; Phillips’ Mineralogy.