284 Transactions. — Geology. 



Art. XLVII, — On the Formation of Moimtains ; a Reply to the Rev. 

 0. Fisher. By Capt. F. W. Hutton, F.G.S. 

 [Read iefore the Wellington Philosophical Society, \st September, 1873.] 

 Having, at the last meeting, been requested by the President to lay before the 

 Society my reply to the Rev. O. Fisher's critique, which appeared in the June 

 number of the Geological Magazine, on my previous lecture on the formation 

 of mountains,"" I have now the honour to do so. 



I have, in the first place, to thank Mr. Fisher for recalculating — more 

 correctly, no doubt, than I have done — my table of the altitude of domes, and 

 also for explaining several points which I had not clearly conceived before. 

 Nevertheless, I think that I shall be able to show that his arguments against 

 the theory that I have advocated are not well founded. 



For the sake qf conciseness I will, in what follows, call the theoiy that 

 Mr. Fisher advocates the "contraction theory," meaning thereby the theory 

 of the formation of mountains by the secular cooling and contraction of the 

 earth ; while I will call the theory that I advocate the " deposition theory," 

 by which I mean the theory of the formation of mountains by the removal of 

 matter from one portion of the earth and its deposition on anotlaer portion. 

 In my lecture I called this latter the " Herschel-Babbage" theory, bixt I have 

 since ascertained that Mr. Scrope was the first to suggest it, and it has there- 

 fore no right to the name that I applied to it. 



(a.) The first argument that Mr. Fisher adduces against the deposition 

 theory is, that any lateral pressure of expansion must be taken as strictly 

 horizontal, and could not cause an upward rising. But the pressure relied on. 

 by Mr. Fisher to produce mountains is just as horizontal as the pressure 

 produced by expansion, and if a cube foot of rock would be simply compressed 

 by the horizontal pressure caused by expansion, why should not the efiect 

 be the same if the horizontal pressui-e was produced by the contraction of the 

 nucleus ? Practically we know that a perfectly hoi'izontal sheet of dry paper 

 stretched on a board will wrinkle when its dimensions are increased by 

 damping ; and the crust of the earth must do the same nnless it crushes. 

 From observation we know that anticlinal curves have been formed, and that 

 the crust therefore does not always crush up. 



Mr. Fisher also says that " we have no right to consider the crust rigid 

 when regarded in proportions of sufficient dimensions to admit of these lateral 

 pressures being otherwise than sensibly in the same straight line, bvit in 

 opposite directions." In his first paper, however, on the formation of moun- 

 tains (Trans. Camb. Phil. Soc, 1869), he not only says that the portion of the 



* See Trans. ]Sr,Z. Inst., Vol. V., App., p. xxv. 



