536 Henry Woodtoard — Address to the Geologists' Association. 



Mallet/ James Hall/ Sterry Hunt/ Prof. Shaler/ Eev. 0. Tislier/ 

 Prof. J. D. Whitney/ Prof. Le Conte/ Medlicott/ Hntton/ and 

 many others, might be enumerated, to show how large a share of 

 attention has of late been directed to its elucidation. 



It would be quite impossible to give the views of all these writers 

 in detail, but it may be practicable to point out some of the more 

 important of the conclusions at which they have arrived. 



And first it may be well to premise that it appears to have been 

 very generally assumed among geologists that all the phenomena of 

 corrugation of the earth's surface, whether exhibited in mountain 

 ranges or in continents, are to be regarded as effects of one and the 

 same cause, differing only in magnitude. 



It is manifest that it is a matter of first importance, in seeking an 

 explanation of the origin of these phenomena, to determine whether 

 this assumed identity of cause be true or no. If it be a fact that 

 continental elevations and mountain elevations are but degrees of 

 efi'ect of the same cause, then there should be no other differences in 

 the phenomena than those of magnitude, or of features dependent 

 directly upon the magnitude of areas involved in the disturbance ; 

 furthermore, there should be something like a series, at one extremity 

 of which could be placed the greatest relief of continental fold and 

 oceanic depression, and passing gradually to the most inconsiderable 

 flexures. It requires no very careful examination to bring the 

 observer to the conviction that these essential features do not exist. 

 The phenomena observable in the two actions are not cognate.^" 



Whether we regard the earth as an oblate spheroid, perfectly solid 

 throughout, or as having a more or less thick crust and a fluid 

 interior, we are justified in considering it as suffering from cooling 

 by radiation, and contracting in a more or less degree from a time 

 long antecedent to the formation of the very oldest metamorphic or 

 sedimentary deposits with which we are acquainted. 



If the material of the globe were homogeneous, and therefore of 



^ " The Eruption of Vesuvius in 1872," by Prof. Palmieri, with Notes and Intro- 

 ductory Sketch of Terrestrial Vulcanicity, by Eobert Mallet, F.E.. S. Loudon, 

 Asher & Co., 1873. 



2 Hall's Palaeontology of New York. See abstract of Prof. Hall's views by Prof. 

 Dana, Sillimau's Journal of Science, 1873, vol. v. no. 29, p. 347. 



3 Prof. T. Sterry Hunt, on " The Origin of Continents," Geol. Mag. 1867, Vol. 

 IV. p. 223. " Chemistry of the Primeval Earth," ibid. 1867, Vol. IV. pp. 357 and 

 477. "On the Probable Seat of Volcanic Action," Geol. Mag. 1869, Vol. VI. p. 

 245; ibid. 1870, Voh VII. p. 60. 



* Prof. Shaler, "Formation of Mountain Chains," Geol. Mag. 1868, Vol. V. 

 p. 511. 



5 Eev. 0. Fisher, " On the Elevation of Mountain Chains," Geol. Mag. 1868, 

 Vol. V. p. 493, and 1873, Vol. X. p. 248. 



6 Prof. J. D. Whitney, " On Mountain Building," p. 101. 



^ Prof. Le Conte in Silliman's American Journal of Science, 1872, vol. iv. no. 

 23, p. 345, and no. 24, p. 460. 



8 H. B. Medlicott, " On the Alps and Himalayas," Quart. Journ. Geol. Soc. 1868, 

 vol. xxiv. p. 34. 



8 Captain F. W. Button, "On the Formation of Mountains," Geol. Mag. 1873, 

 Vol. X. p. 166. 



10 Prof. Shaler, Geol. Mag. 1868, Vol. V. p. 514. 



