A. VaugJian — Corrugation of the Earth'' s Surface, 267 



of compression. Thus any relief, sought for by the breaking of 

 the crust, can only be found in the pushing of one portion over 

 the other ; that is to say, in the production of reversed faults. 

 Normal faults could find no place as consequences of such a 

 system of earth movement. 



To pass on now to give what we think to be a possible and 

 adequate explanation — 



Let us suppose that some large area on the earth's surface is at 

 considerably less distance from the centre than the surrounding 

 regions, and that furthermore the surface rocks in such an area are 

 maintained at a very low temperature. It follows that under such 

 an area the surfaces of equal temperature will be at once more 

 numerous and more crowded than under the surrounding regions — 

 more numerous because, the surface being kept at a lower mean 

 temperature, the range of temperature from the interior to the 

 surface is greater and more crowded because the distance from the 

 centre to any point of our hypothetical area is less than in 

 the surrounding areas. In this case the distance between two 

 points in the same radius, having stated temperatures, will be less 

 than in the regions surrounding the area. In consequence, the 

 transference of heat from one point to the other will be greater ; 

 or in other words the loss of heat will be greatest under the 

 depressed area. Thus beneath such an area contraction will proceed 

 at a faster rate. 



In this place we wish to point out, once for all, that we shall 

 simply consider the effects of contraction upon the nucleus which 

 we imagine to be practically homogeneous at equal distances from 

 the centre. We shall further assume that the overlying crust, being 

 formed of heterogeneous materials, will follow a sinking interior 

 without any rucking, for the reasons given at length above. 

 This distinction in geneity between crust and nucleus probably 

 means no more than that the materials composing the originally 

 homogeneous surface shells have been rearranged by agencies, with 

 which we are not now concerned, to form a heterogeneous crust. 

 It will further appear, on carefully considering the areas under 

 discussion, that the thickness of the crust may be considered to be 

 at least small. 



From the faster contraction which we have shown must take place 

 under such an area, two results necessarily follow. In the first 

 place there will be a great strain upon the rocks bordering upon the 

 depressed area, since the tendency of contraction must necessarily 

 be to draw them closer together. The effect of this strain will 

 necessarily be in the direction of lessening the rapidity of descent 

 from the elevated to the depressed areas, and in this attempt 

 pressure will be produced on the underlying rocks. Secondly, 

 on account of this very resistance to contraction, any arc traced 

 on the area, being in the form of a broad arch, whose centre 

 is approximately the centre of the earth, will in attempting to 

 contract bend inwards so as to lessen its curvature, and consequently 

 shorten its length. In performing such a movement, the underlying 



