For example, is it not possible that, at the prodigious temperature which would seem to exist at 100 miles below the surface, all the metallic bases may behave as mercury does at a red heat, when it refuses to combine with oxygen; while, nearer the surface, and therefore at a lower temperature, they may enter into combination (as mercury does with oxygen a few degrees below its boiling-point) and so give rise to a heat totally distinct from that which they possess as cooling bodies? And has it not also been proved by recent researches that the quality of the atmosphere may immensely affect its permeability to heat; and, consequently, profoundly modify the rate of cooling the globe as a whole? I do not think it can be denied that such conditions may exist, and may so greatly affect the supply, and the loss, of terrestrial heat as to destroy the value of any calculations which leave them out of sight. My functions as your advocate are at an end. I speak with more than the sincerity of a mere advocate when I express the belief that the case against us has entirely broken down. The cry for reform which has been raised without, is superfluous, inasmuch as we have long been reforming from within, with all needful speed. And the critical examination of the grounds upon which the very grave charge of opposition to the principles of Natural Philosophy has been brought against us, rather shows that we have exercised a wise discrimination in declining, for the present, to meddle with our foundations. FOOTNOTES: [39] On Geological Time. By Sir W. Thomson, LL.D. Transactions of the Geological Society of Glasgow, vol. iii. [40] The Theory of the Earth, vol. i. p. 173, note. [41] Ibid. p. 281. [42] Ibid. p. 371. [43] The Theory of the Earth, vol. i. p. 200. [44] The Theory of the Earth, vol. i. pp. 16, 17. [45] The Theory of the Earth, vol. i. p. 223. [46] Principles of Geology, vol. ii. p. 211. [47] Principles of Geology, vol. ii. p. 613. [48] "Man darf es sich also nicht befremden lassen, wenn ich mich unterstehe zu sagen, dass eher die Bildung aller Himmelskoerper, die Ursache ihrer Bewegungen, kurz der Ursprung der ganzen gegenwaertigen Verfassung des Weltbaues werden koennen eingesehen werden, ehe die Erzeugung eines einzigen Krautes oder einer Raupe aus mechanischen Gruenden, deutlich und vollstaendig kund werden wird."--KANT'S _Saemmtliche Werke_, Bd. I. p. 220. [49] Grant ("History of Physical Astronomy," p. 574) makes but the briefest reference to Kant. [50] "Allgemeine Naturgeschichte und Theorie des Himmels; oder Versuch von der Verfassung und dem mechanischen Ursprunge des ganzen Weltgebaeudes nach Newton'schen Grundsatzen abgehandelt."--KANT'S _Saemmtliche Werke_, Bd. i. p. 207. [51] Systeme du Monde, tome ii. chap. 6 [52] Kant's "Saemmtliche Werke," Bd. viii. p. 145.