118 THE WONDERFUL CENTURY. 



mountain ranges are being lowered at perhaps ten times 

 the above average rate, and many mountain peaks and 

 ridges perhaps a hundred times. 



Examples of the rapidity of denudation as compared 

 with earth-movements are to be found everywhere. In 

 disturbed regions, faults of many hundreds, and some- 

 times even thousands of feet, are not uncommon; yet 

 there is often no inequality on the surface, indicating 

 that the dislocation of strata has been caused by small 

 and often-repeated movements, at such intervals that 

 denudation has been able to remove the elevated portion 

 as it arose. Again, when the strata are bent into great 

 folds or undulations, it is only rarely that the tops of the 

 folds correspond to ridges and the depressions to valleys. 

 Frequently the reverse is the case, a valley running 

 along the anticlinal line or structural ridge, while the 

 synclinal or structural hollow forms a mountain top; 

 while, in other cases, valleys cut across these structural 

 features, with little or no regard to them. This results 

 from the fact that it is not mountains or mountain ranges, 

 as we see them, which have been raised by internal 

 forces, but a considerable area, already perhaps much 

 disturbed and dislocated by earth-movements, has been 

 slowly raised till it became a kind of table-land. From 

 its first elevation above the sea, however, it would have 

 been exposed to rainfall, and the water, flowing off in the 

 direction of least resistance, would have formed a num- 

 ber of channels radiating from the highest portion, and 

 thus establishing the first outlines of a system of valleys, 

 which go on deepening as the land goes on rising, often 

 quite irrespective of the nature of the rocks beneath. 

 This explains the close resemblance in the general ar- 



