GENERAL CONSIDERATIONS. 133 



area. How then were the other four miles of strata deposited above 

 them? Put briefly, the objection to the theory is this, that, if sedi- 

 mentation had the effect claimed for it, it would very quickly defeat 

 its purpose by stopping sedimentation in that area. 



Again and again we find the author declaring with fresh assurance 

 that it has been proved that mountain ranges have been areas of great 

 sedimentation. In answer to this I would urge that it is only in 

 mountainous parts that great thicknesses of strata can be actually 

 observed by us ; and that we frequently know nothing of the depth to 

 which the sedimentaries reach beneath the flat or gently undulating 

 areas of continents. 



Finally, even if great sedimentation should be proved to be a 

 characteristic mountain feature, I should rather regard it as the effect 

 than the cause of the mountains. Denudation acts more powerfully 

 on a mountainous region than elsewhere, for obvious reasons. Thus, 

 the sedimentaries might be thicker in the neighbourhood than far 

 away. When, therefore, further upheaval of the mountain mass goes 

 on, these strata will be incorporated with it, and fresh ones then 

 deposited. The core of the mountain range in a rising area is ever 

 being converted and redistributed in the form of fresh sediment 

 round about the flanks, which then once more are upheaved. So that, 

 as in the case of the Himalaya, the range continues growing by fresh 

 additions to itself, like a coral, by the incorporation of its offspring 

 with itself. 



But leaving these generalizations, which I have shewn to be fal- 

 lacious, let us turn to more concrete statements regarding actual 

 mountain ranges. In Chapter V, Mr. Mellard Reade writes — "It has 

 "been a subject of wonder to more than one eminent geologist that 

 " all the greatest mountain ranges are, geologically speaking, so com- 

 11 paratively modern. The Himalaya, the Andes, the Alps and the 

 " mountains of the Caucasus have been to the larger extent upheaved 

 " in Tertiary times." The reason he gives for this is that the youngest 

 mountain ranges have been less exposed to destructive denudation, 

 which has, on the other hand, almost levelled all the ranges of moun- 



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