342 RELATIVE ANTIQUITY [Ch. XXIV. 



elevation at a certain epoch in the earth's history, namely, 

 between the deposition of the chalk and that of the tertiary 

 formations; for the former are seen in vertical, curved, and 

 distorted beds on the flanks of the chain, while the latter rest 

 upon them in horizontal strata at its base. 



The only proof offered of the extreme suddenness of the 

 convulsion is the shortness of the time which intervened 

 between the formation of the chalk and that of the tertiary 

 strata. ' For it follows,' we are told, ' from the unconformable 

 position of two systems of beds, the inclined and the horizontal, 

 that the elevation of the former has not been effected in a 

 continuous and progressive manner, but that it has been pro- 

 duced in a space of time comprised between the periods of 

 deposition of the two consecutive rocks, and during which no 

 regular series of beds was formed ; in a word, that it was sudden 

 and of short duration V 



We are prepared to show that the Pyrenees cannot be 

 assumed to have risen, as M. de Beaumont imagines, in the in- 

 terval between the period of the chalk and that of the tertiary 

 strata ; for we can only say that the movement took place after 

 the commencement of the chalk epoch, and before the close 

 of the Miocene tertiary period. But, first, let us suppose the 

 premises of our author to be correct, and let us permit him to 

 exclude the whole period of the chalk, on one hand, and of the 

 tertiary formations in contact with it on the other ; what will 

 then be the duration of the interval ? We can only estimate 

 its importance by ascertaining what description of chalk is 

 found on the flanks of the Pyrenees, and what horizontal ter- 

 tiary formations at their base. 



Now the beds called chalk, although they differ widely in 

 mineral composition from the white chalk with flints of 

 England and France, contain the same species of fossil shells, 

 and may, therefore, on that evidence, be referred to the same 

 age f . On the other hand, the horizontal tertiary strata at the 



* Phil. Mag. and Annals, No. 58, new series, p. 243. 



f The fossils which I collected in company with Captain S. E. Cook, R. N., 



