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 *.' 
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, E. N., 
