GENERAL CONSIDERATIONS. 135 



&ny theory or prejudicing any, it seems to me that a mountain-range 

 must have in some sort a life-history, which may, in common with 

 that of animals, plants and crystals, be divided into periods of growth, 

 of maturity, and of decay. Long ago, as the result of the principles 

 established by Sir Charles Lyell, cataclysms such as would heave a 

 mountain-chain into immediate being have been discarded as pre- 

 posterous fables only fit for the childhood of geology. Whatever 

 be the view of the cause and the mode of working of the forces 

 which wrinkle up the earth's crust into the majestic plications form- 

 ing most of the larger ranges of the world, there is but one unani- 

 mous opinion that it came about gradually and not abruptly. But in 

 this process of growth a mountain-range is opposed by the action of 

 denudation. It therefore follows that, if a mountain-chain is to rise 

 at all, it must be by its inherent growing forces, whatever they may 

 be, ever becoming more and more intense and winning in the strug- 

 gle with the opposing forces of denudation ; and it also follows that, if 

 ever a mountain-chain is to succumb to the levelling processes em- 

 braced by the general term denudation, it must be by the inherent 

 growing forces of the mountain having reached their maximum, and 

 having in turn become feebler and feebler until finally they are altoge- 

 ther extinct, and the once stupendous mountain is worn down to the 

 level of the sea. 



So far I have no doubt Mr. Mellard Reade will go with me ; he, in 

 common with every one, must admit that the loftier mountains of the 

 world must be at, or near, their maturity; whilst those of less altitude 

 must be either on their way to become more lofty, or must be declin- 

 ing after having reached their maximum of elevation : — herein lies the 

 real difficulty , namely ', to distinguish between a mountain-range pro- 

 gressing towards full development and one retrograding towards 

 extinction. 



It therefore seems in the highest degree improbable that the 

 greatest mountain-ranges are, geologically speaking, comparatively 

 modern. On the contrary, we should expect that being at the period 

 of their fullest development they must be, geologically speaking, of 



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