26 Cajpt. F. W. Button — On the Formation of Momita'ms. 



the Deposition theory, he says (Geol. Mag, Vol. X. p. 249) that the 

 thrust can only be supposed to extend to an infinitesimal distance. 



2. From the absence of any weight on the compressed rocks, from 

 the impossibility of one part slipping horizontally over another, 

 and from the absence of any support if one part should rise up into 

 an anticlinal, we may, I think, confidently assert that the crust of 

 the earth would simply crush up from the effect of contraction, and 

 rise uniformly over the whole surface. Mr. Fisher's formula for the 

 elevation should therefore be ^ = Zc e, instead of li = r Ic m e. 



3. If, however, for the sake of argument, it be granted that 

 the strata did not crush, but rose up along the lines of least re- 

 sistance, it seems to me that these lines would take radiating 

 directions from an area of depression ; and that when these lines 

 were established, whatever might be their direction, the elevation 

 should be continuous on them. The theory therefore seems to 

 offer no explanation of oscillations of level, unless the Deposition 

 theory is called to its aid, as Mr. Fisher seems inclined to do. Prof. 

 Dana, however, when stating the Contraction theory (Greology, 1863, 

 p. 718, etc.), appears to see no difficulty from this cause, but he 

 gives no explanation of the phenomenon. 



4. Also, the same being granted as before, as the upper beds must 

 undergo the greatest compression, the foldings would commence on 

 the surface and be propagated downwards in decreasing amount. 

 But as all sedimentary beds must at one time have been at the 

 surface, and as the whole of the surface contracts, it follows that all 

 strata should be contorted in proportion to their age;^ whereas we 

 know that there are large districts in Eussia and North America 

 formed of undisturbed Palseozoic rocks, while in the Alps, etc., we 

 have highly-contorted Tertiary beds. 



5= The theory also entirely fails to account for strata being 

 elevated without disturbance, unless we suppose such an enormous 

 amount of horizontal slipping of one bed over another as is mani- 

 festly impossible. 



6. If, however, as appears to me to be certain, the rocks must 

 crush, and rise tolerably uniformly, it is evident that the theory is 

 quite inadequate to account for mountains ; because, as the con- 

 traction is universal, the sea would rise more than the land, and the 

 result would be that after the contraction, the sea would stand higher 

 above the land than it did before. If, therefore, we consider the 

 earth when the crust was first formed, and when it was surrounded 

 by a universal ocean, we see that no land could rise above the water 

 from contraction, but that, on the contrary, the ocean would gradually 

 deepen. 



7. Mr. Fisher assumes, without giving any reasons, that since the 

 date of the present surface-features of the earth, a shell 500 miles in 

 thickness has contracted as much as rock would do in passing from 

 a fused to a devitrified state. But is this a reasonable assumption ? 

 I think not. It is certainly quite as reasonable to suppose, with 



1 Because the older the stratum, the larger must be the proportional space over 

 which it was originally spread. 



