SOS M. D'OMAtius D'Halloy, «^r. 



abundant rock in particular countries, ■without excluding the 

 idea that this rock may be accompanied by other formations. 

 Thus, for example, though the passage from the primordial 

 to the secondary rocks rarely takes place without presenting 

 penean deposites, the latter have only been represented 

 where they were known alone to cover a surface so exten- 

 sive as not to overcharge the map with details which would 

 injure the general effect. 



Neither has any attention been paid to the patches of 

 mastuzootic deposites which cover almost all other forma- 

 tions, nor those superficial deposites of loose matters which 

 generally cover all those rocks on which vegetation has esta- 

 blished itself. 



The greater part of the observations which have served 

 for the formation of that part of the map containing the 

 South of France, going back to an epoch in which there was 

 not a very clear idea formed of the divisions now established 

 among limestone rocks, this part of the work greatly re- 

 quires revision. That which regards the Alps, the Pyrenees, 

 and the Cevennes, may also be considered as a sketch of the 

 manner in which I regard the geological nature of these 

 mountains, rather than an exact representation of the places 

 on which the different rocks appear ; for independently of 

 our being in want of observations on this subject, it is known 

 that mountainous countries rarely afford demarcations. It 

 should in the last place be added that the north of Germany 

 has been traced on the map from the observations published 

 by German authors, and solely with the view of shewing the 

 connection of the different masses of rocks. 



