348 RELATIVE ANTIQUITY I Ch. 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 island, 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 w r here the disturbed and 

 undisturbed strata in contact are not very nearly of the same 

 age, or, as he expresses it, ' where they arc 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 Juiun. of Sci., No. 2, third scries, p. 118. The second part, 

 I believe, is not yet published, 

 t Ibid., p. 120. 



