According to one view, | According to the other view, | 1. The volumes of each gas | 1. The volume of each gas found at the surface of the | found at the surface of earth are proportional to | the earth, _multiplied by the whole weights of the | its specific gravity_, is respective atmospheres. | 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 | 2. The altitude of each atmosphere differs from that | atmosphere is the same, and of every other, and the | the proportion of each in the proportions of each in the | compound atmosphere, is the compound atmosphere gradually | same at all elevations. vary in the ascent. | | 3. When two atmospheres are | 3. When two atmospheres mixed, they take their places | are mixed, they continue according to their specific | so without the heavier gravity, not in separate | manifesting any disposition to strata, but intermixedly. | separate and descend from the There is, however, a separate | lighter. stratum of the specifically | lighter atmosphere at the | summit over the other. | [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_. [218] GENTELE’S Reports of the Stockholm Academy.