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Show 336 SECONDARY FORMATIONS. [Ch. XXIII. b · upti.O ns . b ut at som e points~ as in the Hebrides, su rnarme er ' the theatre of volcanic action. it seems that the same ocean was * h . W 1 e menti.O ne d m. t 1l e first volume · , that as t e1 an.c ient e .l av occurre d m. succes sion ' sufficient time usua ly mter-erup · tiOnbse tween t h em t o al low of the accumulation of many vsuebmanqgu eous strata, so a1 s 0 should we infer that 1s ubt.e rrahn ean movements, wh I.C 11 are ano ther portion o.f the vo came p eno-mena, occurred separately and in successiOn. • Chap. v. P· 88 '. an d Second Kdition, p. 100. CHAPTER XXIV. On the t·elative antiquity of different mountain-chains-Theory of M. Elie de Beaumont-His opinions controverted-His method of proving that different cl1ains were raised at distinct periods-His proof that others were contemporaneous- His reasoning, why not conclusive-Ilis doctrine of the parallelism of contemporaneous lines of elevation-Objections-Theory of parallelism at variance with geological phenomena as exhibited in Great Britain-Objections of Mr. Conybeare-How far anticlinal lines formed at the same period are parallel-Difficulties in the way of determining the relative age of mountains. RELATIVE ANTIQUITY OF MOUNTAIN-CHAINS. TIIAT the different parts of our continents have been elevated, in succession, to their present height above the level of the sea, is an opinion which has been graduaJJy gaining ground with tl1e progress of science; but no one before M. Elie de Beaumont had the merit even of attempting to collect together the recorded facts which bear on this subject, and to reduce them to one systematic whole. The above-mentioned geologist was eminently qualified for the task, as one who l1ad laboured industriously in the field of original observation, and who combined a considerable knowledge of facts with an ardent Jove of generalization. But he has been ambitious, we think unfortunately, of anticipating the march of discovery in reference to the comparative antiquity of different mountain-chains and their supposed connexion with changes in the animate world. His speculations diffet· entirely from the conclusions to which we have arrived, and we therefore think it necessary to explain fully the reasons of our dissent. In order to put the reader in possession of the principal points of M. de Beaumont's theory, we shall first offer a brief sketch of them, and then proceed to analyze the data on which they are founded. Vot,lll. z |