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Published online by Cambridge University Press: 01 May 2009
Having been honoured by an invitation to state to your Society the physical principles upon which my Theory of the Origin of Mountain Ranges is founded, I do so with the greater pleasure knowing that it will receive a searching criticism at your hands, from which I hope to derive considerable benefit. My audience hitherto having been mostly geological, the physical principles involved have been to some extent subordinated to geological conditions.
Read before the Liverpool Physical Society, January 29th, 1894.
page 204 note 1 See also Sir W. Thomson, Brit. Assoc. Report, 1876, and Dr. C. H. Darwin, Phil. Trans. 1879, part i. It is considered that the earth is as rigid as steel, or at least glass, from the surface to the centre.
page 206 note 1 These consequences are worked out in a very ingenious manner, considering the time at which it was written, by Babbage in the 9th Bridgwater Treatise, in the Appendix Note F, pp. 182–201. Sir John Herscbel's views, having a somewhat similar bearing, with the addition of what is now called Isostacy, are also given in a letter to Lyell, dated 1836, and published in Note 1, pp. 202–217.
I had not read these remarkably luminous sketches of a theory of elevation and subsidences until long after the publication of my “Origin of Mountain Ranges.” The ideas are far in advance of the times, but are incomplete as not accounting for lateral pressure. Culumnar expansion is the only thing considered.
page 207 note 1 Prof. Joseph Prestwich observes (Proc. Royal Soc. 1866): “With respect to the possibility of change in the thermometric gradient at great depths, it is known that the conductivity of wrought iron diminishes as the temperature increases.” From this he inters that the thermometric gradient may increase at great deaths.
page 208 note 1 See Le Conte—“ Theories of the Origin of Mountain Ranges,” Nature, Oct. 5th, 1893, and my examination thereof, entitled “Genesis of Mountain Ranges,” Natural Science, Nov. 1893.
page 209 note 1 Mr. O. Fisher, taking the temperature of solidification at 4000° F. and the time at 33 million years, arrives at a total radial contraction of 2 miles. If the temperature of solidification were 7000° F. and the time 98 million years, the total radial contraction would be 6 miles. These calculations cover the whole of the time since first solidification, whereas the time I am dealing with is from the beginning of the Cambrian, probably not half the time that has elapsed since the first solidification of the globe.-See Fisher, , Phil. Mag. 1888, pp. 7–20.Google Scholar
page 210 note 1 Sir A. Geikie, Pres. Address British Association, 1892.
page 210 note 2 Judd, , speaking of the Alps (Volcanoes, p. 295)Google Scholar, says: “ The united thickness of all sediments accumulated along this great line of subsidence between the Permian and Nummulithic periods probably exceeds 50,000 feet or 10 miles.” Various American authorities estimate that the thickness of the Palæozoic system of the Appalachians reaches 40.000 feet; the Palaeozoics and Mesozoics in the Wasatch 50,000 ; the Cretaceous in the coast ranges of California 20,000 feet, and in Shasta county 30,000 feet; the Palaeozoic and Mesozoic of the Uinta 30,000.—See Le Conte—Theories of the Origin of Mountain Ranges, Journal of Geology, 1893, p. 544.Google Scholar
page 213 note 1 ProfPrestwich, Joseph,inan exhaustive discussion of underground temperature observations, suggests that 45 feet per degree is nearer to the true normal.—Proc. Royal Soc. 1886.Google Scholar