138 GEOLOGY [Chap. IX 



Letter 491 Europe being now at rest, with one part undergoing move- 

 ment. How it is, that from this you can argue that the 

 one part which is now moving will have rested since the 

 commencement of the Glacial period in the proportion of 

 four to one, I do not pretend to see with any clearness ; but 

 does not your argument rest on the assumption that within 

 a given period, say two or three million years, the whole of 

 Europe necessarily has to undergo movement ? This may be 

 probable or not so, but it seems to me that you must explain 

 the foundation of your argument from space to time, which 

 at first, to me, was very far from obvious. I can, of course, 

 see that if you can make out your argument satisfactorily to 

 yourself and others it would be most valuable. I can imagine 

 some one saying that it is not fair to argue that the great 

 plains of Europe and the mountainous districts of Scotland 

 and Wales have been at all subjected to the same laws of 

 movement. Looking to the whole world, it has been my 

 opinion, from the very size of the continents and oceans, and 

 especially from the enormous ranges of so many mountain- 

 chains (resulting from cracks which follow from vast areas of 

 elevation, as Hopkins * argues) and from other reasons, it has 

 been my opinion that, as a general rule, very large portions 

 of the world have been simultaneously affected by elevation 

 or subsidence. I can see that this does not apply so strongly 



1 William Hopkins, F.R.S. (1793-1866) entered Peterhouse, Cam- 

 bridge, at the age of thirty, and in 1827 took his degree as seventh 

 wrangler. For some years Hopkins was very successful as a mathematical 

 tutor ; about 1833 he began to take a keen interest in geological subjects, 

 and especially concerned himself with the effects of elevating forces 

 acting from below on the earth's crust. He was President of the 

 Geological Society in 1851 and 1852 {Quart. Journ. Geo/. Soc, Vol. 

 XXIII., p. xxix, 1867). See "Report on the Geological Theories of 

 Elevation and Earthquakes." By William Hopkins. Brit. Assoc. Rep., 

 1847, PP- 33-9 2 ; also the Anniversary Address to the Geological Society 

 by W. Hopkins in 1852 {Quart. Journ. Geo/. Soc, Vol. VIII.) j in this 

 Address, pp. lxviii et seg.) reference is made to the theory of elevation 

 which rests on the supposition "of the simultaneous action of an up- 

 heaving force at every point of the area over which the phenomena of 

 elevation preserve a certain character of continuity . . . The elevated 

 mass . . . becomes stretched, and is ultimately torn and fissured in 

 those directions in which the tendency thus to tear is greatest ... It is 

 thus that the complex phenomena of elevation become referable to a 

 general and simple mechanical cause. . . ." 



