348 
RELATIVE ANTIQUITY 1 
ICh. XXIV. 
south, cannot be strictly said to be parallel, since they would, 
if prolonged, cross each other at the poles. 
Objections of Mr. Conybeare. — An inquiry was proposed, in 
1831, by the British Association for the Promotion of Science, 
* whether the theory of M. Elie de Beaumont, concerning the 
parallelism of lines of elevation of the same geological era, is 
agreeable to the phenomena as exhibited in Great Britain ? ' 
Mr. Conybeare, in the first part of his report, in answer to this 
inquiry *, points out many lines of distinct ages in England 
which are exactly parallel, and others which, according to the 
rules laid down by M. de Beaumont, ought to agree in age with 
certain continental chains, and yet do not, having an entirely 
different direction. He imagines that the general strike of the 
secondary strata of our islands from N. E. to S. W., has been 
the result, not of any violent or single convulsion, but, on the 
contrary, of ' a gradual, gentle, and protracted upheaving, con- 
tinued without interruption during the whole period of the 
formation of all these strata.' 
The same author has also adverted to some of the difficulties 
attending the exact determination of the geological epochs of 
the elevation of each chain, especially where the disturbed and 
undisturbed strata in contact are not very nearly of the same 
age, or, as he expresses it, 6 where they are not terms imme- 
diately following one another in the regular geological series f.' 
We were forcibly struck with the uncertainty arising from this 
cause during a late tour, when we discovered that at the eastern 
end of the Pyrenees, on the side of France, tertiary strata of the 
older Pliocene epoch abut against vertical mica-schist ; while 
at the western extremity of the same mountain-range we find the 
disturbed series to consist of chalk, the undisturbed of Miocene 
strata. The chain is then lost in the sea, and we are precluded 
from pushing our investigations farther to the westward ; but 
* Phil. Mag. and Journ. of Sci., No. 2, third series, p. 118. The second part, 
I believe, is not yet published, 
t Ibid., p. 120. 
