SOO M. D'Omalius D'Halloy on a 



where it does not appear that the primitWe disposition of the 

 beds has been deranged ; but can we place true confidence 

 ill the superpositions observed in the primordial rocks in 

 which the beds are often vertical ? It is an opinion very 

 geuerally adopted, that these beds have originally had a 

 horizontal or slightly inclided position, and that they owe 

 their present situation to violent causes : now, a cause sufiB- 

 ciently violent to throw a bed into a vertical position, may 

 also have given it an inclination in a contrary direction, and 

 consequently have placed that beneath which was at first 

 above ; we may the more easily admit this mode of super- 

 position, as the numerous accidents of the inclined beds 

 shew that their disturbance has not been the result of one 

 catastrophe alone. 



I am fully aware that the partisans of the exclusive ante- 

 riority of crystallized rocks, may retort this argument, by 

 attacking the conclusions which I draw from the position of 

 some of these rocks abeve those containing organic remains ; 

 but if they grant this principle, the whole of their system will 

 fall to the ground, since the series of formations they adopt 

 is only founded on these superpositions ; the character of the 

 absence of organic remains is but a negative fact of little im- 

 portance in this respect, since the study of secondary rocks 

 has proved that the deposites of a siliceous nature and those 

 abounding in crystallized portions, commonly contain few 

 or no organic remains, as if the liquids from which these de- 

 posites were made had driven the animals away. 



The common divisions of primordial rocks not being ap- 

 plicable to the map of the countries on which I was en- 

 gaged, I had the idea of substituting another, founded on 

 the circumstance that we might recognise three bands in 

 these rocks, which are distinguishable for peculiar charac- 

 ters. One of these bands, situated in the north, and which 

 comprises Britanny, and the countries between the Scheldt, 

 the Weser, and the Hartz, is remarkable for the abundance 

 of slates, and transition limestone found there. 



Another, on the south, which comprises the Pyrenees, 



