Capt. F. W. Button — On the Formation of Mountains. ^3 



the " Deposition theory," by which I mean the theory of the forma- 

 tion of mountains by removal of matter from one portion of the earth 

 and its deposition on another portion.^ 



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

 sition theory is that any lateral pressure of expansion must be taken 

 as strictly horizontal, that the pressure on one side would exactly 

 balance that on the other, and that no upward rising would take 

 place. But the pressure relied upon by Mr. Fisher for producing 

 mountains is just as horizontal as the pressure produced by expan- 

 sion ; and if a cubic foot of rock would be simply compressed by the 

 horizontal pressure caused by expansion, why should not the effect 

 be the same if the horizontal pressure was produced by the contrac- 

 tion of the nucleus ? Further on in his paper (p. 250), Mr. Fisher 

 allows that the direction of the forces would be the same in both cases. 

 Practically we know that a perfectly horizontal sheet of dry paper 

 stretched on a board will wrinkle up when its dimensions are in- 

 creased by damping it, and that a perfectly straight bar of iron, 

 firmly fixed at each end, will bend if heat is applied to it. Mr. G. 

 Maw has also given (Geol. Mag. 1868, Vol. V. p. 294) an excellent 

 example of the displacement of the coping-stone of a wall by expan- 

 sion ; and the crust of the earth must do the same unless it crushes. 

 From observation we know that anticlinal curves have been formed, 

 and therefore that the crust 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, but in opposite directions." But in his first paper on 

 the Elevation of Mountains (Trans. Cam. Phil. Soc. 1869, xi. p. 4), 

 he not only says that the portion of the " rigid " spherical shell that 

 he is considering is kept in equilibrium by its attraction towards the 

 centre {i.e. its weight), and by the pressures tangential to great 

 circles round the circumference of the shell (e.e. the lateral thrust of 

 the arch or dome), but he calculates the amount of the latter, and 

 shows that it is independent of the size of the shell, — except so far 

 as the size alters the weight ; and I really fail to see the difference 

 between this and stating, as I did, that each portion of the rigid 

 crust is partly maintained in its place by the lateral thrust of the arch. 

 (&.) Mr. Fisher's next argument is that the rocks would crush 

 under this pressure, and not rise up in anticlinals. But in order to 

 crush there must be some space to crush into ; and, by the Deposition 

 theory, it is the lower beds that are undergoing compression, while 

 the upper are not ; and in order to relieve the compression, the upper 

 beds must be forced up, either by fractures being formed and certain 

 parts only raised, or else altogether into one or more dome-shaped 

 elevations.^ As the last requires much the least work, it is the way 

 in which the pressure would be relieved. 



1 I find that this theory was first suggested by Mr. Scrope (Volcanoes, 1st edition, 

 1825, p. 30), so that it has no right to the name of the Herschel-Babbage theory, as 

 I previously called it. 



2 To prevent misconception, I must explain that by a dome-shaped elevation I do 



