of the Farallelism of Contemporaneous Lines of Elevation. 413 



collect the scattered evidence we possess on the subject to 

 which it refers, and to indicate the points in which that evi- 

 dence is defective, than the attempt to deduce certain con- 

 clusions from materials so avowedly imperfect; and I will 

 therefore content myself at present with observing, that while 

 the evidence of the parallelism of the principal transition 

 chains appears undoubtedly favourable to M. de Beaumont's 

 hypothesis, I am altogether unable to reconcile to that hy- 

 pothesis the facts I have stated, with regard to the anticlinal 

 lines bounding the coal-fields of South Wales, the Forest of 

 Dean, and Bristol, where we have seen the very same lines of 

 elevation inflected from an E. and W. to a N. and S. bearing: 

 and I would further observe, that to me the subject appears 

 to embrace a much wider field of consideration ; we have not 

 only to consider the results of the more violent paroxysmal 

 convulsions which have affected the strata at different epochs, 

 but the more general and gradual elevation which the phas- 

 nomena of the post-carboniferous rocks indicate to have pro- 

 ceeded very gently, and to have produced very little relative 

 disturbance in the strata so elevated. 



Finally, when the theory of parallel chains with reference 

 to the points of the compass is so extended as to embrace 

 half the circumference of the globe, (as is done in the conclu- 

 sion of M. de Beaumont's memoir*,) I would inquire, Do we 

 not require a more exact definition of the sense in which the 

 term parallel is here used? The parallels of latitude are, in- 

 deed, strictly parallel lines ; but the meridians are great cir- 

 cles passing through the centre of the planet, and no two of 

 them can possibly be parallel to one another : thus, an east 

 and west chain in central Africa and Iceland are parallel* in 

 every acceptation of the word ; but north and south chains in 

 the old anil new continents, the Ural mountains, for instance, 

 and the Cordilleras of the Andes, are not parallel in the same 

 sense ; the two systems of lines in no manner bear the same 

 relations to the spheroidal form of the planet, the meridional 

 system having constant reference to its centre, which the 

 parallels of latitude always neglect. If, therefore, we are to re- 

 ceive the idea of parallel chains, not as strictly parallel to 

 each other, but as having always similar bearings with regard 

 to the points of the compass, must we not further demand 

 some explanation why north and south chains are thus deter- 

 mined in their elevation by their relations to the centre of the 

 planet, while the east and west chains do not follow that re- 

 lation ? 



[ ■ Sec Phil. Mag. ami Annals, N.S. vol. x |>. 259, in an extract from 

 M. <I(j Beaunioni'a Essay.— Edit.] 



