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Show 348 RELATIVI~ ANTIQUITY LOh. XXIV. south, cannot be strictly said to be parallel, since they would, if prolonged, cross each othet· 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, continued 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, ' where they are not terms immediately following one another in the regular geological series t.' 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. 'fhe second part, I uelieve, is not yet 11ublished. t lbid.1 p. 120, Ch. XXIV.] OF MOUNTAIN-CliAINS. 349 if we c.o uld follow the strike of the beds in their subm m· ~~ longatwn,. who shall say that the tilted group might not be found to mclude strata newer than the chalk, the horizontal beds older than the Miocene ? Supposed instantaneous rise of a mountain-chain.-r Every· thing .shows, says M. Elie de Beaumont, that the instantaneous ele~atwn of the beds of a whole mountain-chain is an event of a different order from those which we daily witness •'!;..' We observe ~ith pleasur~ the rejection, by }\,fr. Conybearc, of the hypothesis that the disturbances affectinrr lar()'e . • • • o b geogra-phic~! districts have ~een produced at one blow, rather than by a senes of shocks whiCh may have occurred at intervals through a long period of ages, and that he contends for the O'reatcr probability of successive convulsions, on the ground tha~ such an hypothesis is most conformable to the only analogy presented by actual causes-' the operations of volcanic forces ·1·., Modern volcanic lines not parallel.-By that analogy we are led to suppose tha~ the li~1es of convulsion, at former epochs, were far from bemg umform in direction, for the trains of active volcanos are not parallel, as every one is aware who has studie~ V~n Buch's masterly survey of the general range of vo1camc hnes over the globe!, and the elevations and subsidence~ caused. by moder~ earthquakes, although they may sometimes run 111 parallel hnes within limited districts, have not been observed to have a common direction in distant and independent theatres of volcanic action. d We do not doubt that in many regions the ridges, troughs, an fissures caused by modern earthquakes' are , to a cer t m· n extent, parallel t'() each other, but only within a limited range of country; and such appears to have been the case · d' · 111 many Istncts at former eras. The anticlinal lines of the '\Veald Valley, before alluded to, and of the Isle of Wi()'ht · h . b , may, In t 1s manner, have been contemporaneous that · t b 1 , c 1s osay, ot 1 * .Phil. Mag. ancl Annals, No. 58, new series, p. 243. t Plul. Mag. an<l Jonrn, of Sci., No.2, third series p. 121 +Ph . 1 I • + ys1ca ·Besch. der Canarischen lnseln, Berlin, 1825, |