336 



ELEVATION OF THE GRANITE. 



generally admitted truth, have obtained for it the attention which I 

 think it was justly entitled to, and which it would certainly have re- 

 ceived, had it been announced by any tyro in geology, either in 

 France or Germany. At pages 152, and 153., of the present vol- 

 ume, will be found a brief account of this discovery, which was also 

 republished in the 3d edition of this work ; but it may be proper to 

 give a more full reference to the sections by which the discovery was 

 illustrated, as they serve, not only to explain from what data the rel- 

 ative age of the elevation of different mountain chains may be ascer- 

 tained, but to show that M. Elie de Beaumont has been guided by 

 exactly the same data, in forming his recent conclusions respecting 

 the ages of mountain chains in various parts of Europe. See Plate 

 II. fig. 2. : d, d, d, represent the highly inclined beds of granite 

 and primary rocks of Mont Blanc : the dotted lines represent the 

 supposed extent of the beds before they were broken down by causes 

 that are incessantly wearing them away, as described in the preced- 

 ing chapter : c c, are elevated beds of soft slate, which have under- 

 gone more disintegration than the harder beds of granite : it is in 

 these depressions, called cols, that the passages over the Alps are 

 generally situated. 



The beds b a, b a a, are composed of the secondary formations, 

 from magnesian limestone, to the green sand of the chalk formation. 

 Now, as all these beds rise at nearly the same angle of elevation as 

 the granite, it is evident that they were elevated at the same epoch, 

 which must have been subsequent to the deposition and consolidation 

 of all the secondary beds from a a lo b, that rise up with the granite, 

 and therefore the elevation of the granite of Mont Blanc, was poste- 

 rior to the secondary epoch. Plate II. fig. 4. shows a section of the 

 low granitic and slate rocks of Charnwood Forest, Leicestershire, 

 considerably elevated, b c, c b. On the top of the elevated beds c c, 

 there are a series of nearly horizontal beds of the upper new red 

 sandstone described in Chapter XI. Now as these beds of new 

 red sandstone are of the same age as the lower secondary beds b b, 

 in fig. 2., and were obviously deposited, after the beds of granite 

 and slate rock were elevated, it is obvious that this elevation took 

 place prior to the secondary epoch, and therefore long before the 

 elevation of the granite beds of Mont Blanc. The new red sand- 

 stone not only fills up depressions in the rocks of slate and granite at 

 Charnwood Forest, but also fills some of the valleys at their feet. 



If we admit, what few geologists will deny, that the same secon- 

 dary formations in different European countries were cotempora- 

 neous, it cannot be controverted, that the elevation of the slate rocks 

 and granite in Charnwood Forest, was long prior to the elevation of 

 the granite of Mont Blanc. This is but repeating what I published 

 in 1823 : — a similar position has recently been advanced by M. Elie 

 de Beaumont, much amplified, and illustrated by numerous facts. It 

 would scarcely be possible within the limits allowed for the subject 



