64 GENERAL DISTRIBUTION OF THE 



forms of mountains arc also modified in various ways. 

 It is also observed that, on opposite sides, they have 

 sometimes reverse inclinations ; and thus a mountain 

 formed of stratified rocks alone, may have similar 

 opposing sides, unvaried hy precipices or projecting 

 rocks. Similar effects result from great undulations 

 or curvatures of the strata ; the effects thus produced 

 in mountains, being hence of an analogous nature to 

 those which take place m the lower grounds, but in 

 a more extreme degree. These cases are, however, 

 most frequent where the central parts of mountains 

 or ridges are formed of unstratified rocks ; against 

 which the strata are sometimes found to repose, in 

 opposite ways, and with different inclinations. 



But all mountains are not necessarily generated, 

 either by the protuberance of unstratified rocks or 

 the irregular elevations of stratified ones. On the 

 contrary, many high ones, of which Scotland offers 

 examples on the west coast of Rossshire, are consti- 

 tuted of strata nearly horizontal ; and their forms 

 must then be attributed to that waste visible on their 

 abrupt sides, in consequence of which all those por- 

 tions have been removed, as far as their absence was 

 necessary to the ultimate production of the shapes 

 which they now display. 



The formation of valleys, like that of hills, depends 

 primarily on the elevations of the strata ; and the one 

 is a necessary consequence of the other. Nor is it 

 possible to conceive that original cause wanting ; 

 unless it could be shown that, during the operations 

 which displaced the strata from their original hori- 

 zontal positions, every interval was so filled up as to 

 form a smooth and level surface. Much has been 

 written on a subject which appears too obvious to 



