[198] See a Memoir on the Alps, by Professor Sedgwick and Sir Rod. Murchison, Trans. of Geol. Soc. second ser. vol. iii. accompanied by a map.
[199] See Proceedings of Geol. Soc. vol. ii. p. 334.
[200] It may be observed, that the facts and inferences exhibited in this map bear not merely on the theory of climate above proposed, but serve also to illustrate the views explained in the third book respecting the migration of animals and plants and the gradual extinction of species.
[201] See Sir R. Murchison's Paper on the Alps, Quart. Journ. Geol. Soc. vol. v. and my Anniversary Address for 1850, ibid. vol. vi.
[202] Allgemeine Literatur Zeitung, No. cxxxix. July, 1833.
[203] In this estimate, the space within the antarctic circle is not taken into account: if included, it would probably add to the excess of dry land; for the late discoveries of Capt. Sir James Ross, who penetrated to lat. 78° 10' S., confirm the conjecture of Captain Cook that the accumulation of antarctic ice implies the presence of a certain quantity of terra firma. The number of square miles on the surface of the globe are 148,522,000, the part occupied by the sea being 110,849,000, and that by land, 37,673,000; so that the land is very nearly to the sea as 1 part in 4. I am informed by Mr. Gardner that, according to a rough approximation, the land between the 30° N. lat. and the pole occupies a space about equal to that of the sea, and the land between the 30° S. lat. and the antarctic circle about one-sixteenth of that zone.
[204] See papers by Mr. Smith of Jordanhill, F. G. S., and the author, Proceedings Geol. Soc. No. 63, 1839, also that of Prof. E. Forbes, before cited, p. 86, note.
[205] The theorem is thus stated:—"The eccentricity of the orbit varying, the total quantity of heat received by the earth from the sun in one revolution is inversely proportional to the minor axis of the orbit. The major axis is invariable, and therefore, of course, the absolute length of the year: hence it follows that the mean annual average of heat will also be in the same inverse ratio of the minor axis."—Geol. Trans. second series, vol. iii. p. 295.
[206] Ann. du Bur. des Long. 1834.
[207] Poisson, Théorie Mathémat. de la Chaleur, Comptes Rendus de l'Acad. des Sci., Jan. 30, 1837.