132 Dr Boue 07i the Elevation of' Mountain Chains, 



M. de Beaumont only answers to Mr Sedgwick, that " Lorsque 

 deuK formations semblent passer insensiblement Tune k Pau- 

 tre, il n'y a jamais qu'une tres petite epaisseur de couches, dont 

 la classification puisse rester incertaine, et lorsque certaines 

 espoces de fossiles sont communes k deux formations successives, 

 elles ne forment, en general, qu'*une fraction, souvent meme peu 

 considerable, du nombre total des especes de chacune des deux 

 formations C (p. 619.) Now, this uncertainty in the classifi- 

 cation remains to us not as a consequence of a want of exactness 

 in the system, but as a consequence of the gradual operations of 

 nature. Besides, the whole reasoning of M. de Beaumont re- 

 poses upon the acceptation given to the word formation. Does 

 it mean a deposit, a mass of various deposits, or a group of par- 

 ticular beings ? I suppose M. de Beaumont adopts the second 

 definition, but in that case, descending without fear from the 

 generalizations to examples, we shall easily demonstrate that, for 

 instance, some people have too hastily separated by general re^ 

 volutions the zechstein and the coal formation ; and again, the 

 variegated sandstone, the muschelkalk, and keuper, three de- 

 posits, which, on a large scale, form only a single geological 

 mass. ^ 



M. de Beaumont, foreseeing the objections, agrees entirely 

 with our views, for he acknowledges that " entre les periodes de 

 diverses formations, il y a eu pour le moins des deplacements 

 considerables dans les lieux d'habitation de certains groupcs 

 d''etres organises, en meme temps que dans les lieux de depot de 

 certains sediments;" (p. 619 ) Every one will admit this kind of 

 anodyne revolution is widely different from those general cata- 

 clysms which were said to have produced such a change on the 

 surface of the earth, that new creations were necessary to fill up 

 again the spaces of the earth and seas, which were without beings 

 to inhabit them. The door remains in this way open to every 

 future correction, or to any addition to the actual system of the 

 paleontological distribution into epochs. 



Let us now review the twelve systems of elevation of M. de 

 Beaumont. 



The oldest system of elevation is that of Westmoreland and the 

 Hundsi'ucky and consists of what I consider to have been islands, 

 which had emerged before the formation of the carboniferous and 



