158 Sketch of a Classification 



third is not so generally referred to that origin, I know not 

 how we can deny that it was produced hy a cause somewhat 

 similar to that which produced the others, when we consider 

 its mode of occurrence, more particularly in the Alps and in 

 Italy. 



The geological dates of the elevations of mountains is a most 

 important subject, and one on which M. Elie de Beaumont read 

 a very interesting paper, in June last, before the Institute of 

 France*. His recent observations have tended to confirm his 

 previous remarks on four of these epochs. 1st. That the 

 Ezgeber^e, the Cote d'Or, &c. have been elevated between the 

 epoch of the Jura limestone and the green-sand and chalk. 

 (Groups 5 and 4 of the annexed Table.) 2nd. That the Pyre- 

 nees and Apennines were thrown up between the epoch of the 

 chalk and tertiary rocks (Groups 4 and 3). 3rd, That the 

 Western Alps were raised between the tertiary epoch and the 

 first » terrains de transport" (Groups 3 and 2). 4th. That still 

 later, there was an elevation of mountains, in which were com- 

 prised some in Provence, the Central Alps, &c. 



How far the igneous rocks have been connected with these 

 phenomena remains to be seen ; but, as before stated, it is by 

 no means fair to infer that because not seen on the surface they 

 do not exist beneath. Volcanoes, properly so called, both ex- 

 isting and extinct, seem to have exerted a minor influence in 

 the elevation of strata compared with that exerted by the igne- 

 ous rocks which were shot up previous to the action of these 

 -volcanoes. Elevations of land do, however, take place apparent- 

 ly from the causes that produce volcanoes ; and of these the 

 rise of land noticed in Chili by Mrs. Maria Graham, in conse- 

 quence of the earthquake of 1824, is a striking example. 



Should the annexed Table succeed in calling the attention of 

 geologists to other divisons than those made in the infancy of 

 the science, and grounded, on particular theories, one supposing 

 three great epochs and a transition between the first and second 

 of these ; another considering rocks divisible into two great 

 classes, a primary and secondary, the primary containing or- 

 ganic remains in its upper part,— my object will, as 1 before 

 stated, be fully answered. We are yet acquainted with so 

 small a portion of the real structure of the earth's exposed sur- 

 face, that all general classifications of rocks are premature; and 

 it seems useless to attempt any others than those which are com* 

 -paratively local, calculated for temporary purposes, and of such 

 a nature as not to impede by an assumption of more knowledge 

 than we posseae, the general advancement of geology. 



; * The first part of this paper has been published in the Annates des Scien- 

 ces Naturelles, for September. - 



