358 Influence of Water and Ice on the Earth's Features. 



run, and which are in no sense the result of mechanical violence 

 or upheaval. 



The real aspect of the Alps, if fairly estimated, seems to 

 offer nothing that cannot have been produced by denudation. 

 Yast masses of sedimentary rock, of the older and middle 

 periods, were once deposited horizontally over the granite 

 which now forms the loftiest peaks of the chain. Gradually 

 elevated, and as gradually denuded, all the softer and more 

 yielding rocks have been swept off, to form the newer rocks 

 far away to the north and south. Even when a deep fissure 

 or gorge was originally a fracture, the water has since so com- 

 pletely done its work as to leave abundant evidence everywhere 

 that all the actual forms and details are the result of its action, 

 continued from the day when the torrent first began to wear 

 away a channel, to the hour when it was last examined by the 

 geologist or physical geographer. 



Professor Tyndall has well illustrated this condition by 

 remarking, that if an accurate model of the Alps were taken, 

 a mould taken from it and inverted would exhibit broader and 

 blunter mountains and narrower valleys than the model. In 

 other words, much more has been removed than is left. It is 

 physically impossible that the outline of the Alps, as we now 

 see it, can be merely the result of contraction, fracture, up- 

 heaval, convulsion, or such like causes. The utmost possible 

 allowance for cracks in such an operation, the sum of all the 

 widths of all the cracks in a line a hundred miles in length, 

 lifted 20,000 feet, would not amount to a quarter of a mile. 

 The width of any one of the scores of valleys is well known to 

 be greater than this. The area of the open fissures produced 

 by disruption must be insignificant compared with that of the 

 unfissured crust ; whereas the area of the valleys is far larger 

 than that of the peaks and mountain-summits. There is really 

 no reasonable explanation of this very patent fact, without 

 assuming denudation to have carried away enormously more 

 than it has left ; and unless we suppose the needles of hard 

 rock, and the prominent and picturesque peaks and ridges, to 

 be but the less destructible remains of all that was once there, 

 we must give up the attempt to explain rationally the pheno- 

 mena before us. 



But if it be granted that water, during the elevation of a 

 mountain chain, and while it is yet beneath the waves, carries 

 off by its mechanical power in a fluid state whole piles of strata, 

 comparatively soft as they emerge slowly from the deep; or if, 

 when all that is left is gradually more and more lifted, a large 

 portion is pared away by rain and river action. — what must we* 

 say to another and very different action of the same substance, 

 when, in spite of all that the waves and the rain and the stream 



