On the meaning of the term 'Silurian system' as adopted by geologists in various countries during the last ten years / by Sir Roderick Impey Murchison.

  • Murchison, Roderick Impey, 1792-1871.
Date:
1852
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Licence: Public Domain Mark

Credit: On the meaning of the term 'Silurian system' as adopted by geologists in various countries during the last ten years / by Sir Roderick Impey Murchison. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    of North Wales, had led me by a process of induction, and not by any “ rash generalization,” to adopt these views. In my Discourse of 1843 I used these words in reference to the last publication of Pro- fessor Sedgwick himself:—“ The hope, however, which was enter- tained by my friend, of finding these vastly expanded lower members characterized by peculiar groups of fossils has been frustrated, and, whatever may be the thickness of the lowest palaeozoic division, he now fully admits, that zoologically it is from top to bottom a Lower Silurian Series*.” (1845.) Having ascertained that there was a true fossiliferous base in Scandinavia, Bohemia, and other countries, I then wrote (1845) those earlier chapters in ‘ The Geology of Russia and the Ural Mountains,’ to which my friend makes no allusion, though in them the general order from true “base-lines” was first given, from an unfossiliferous bottom, through the Lower and Upper Silurian and overlying palaeozoic deposits, to the Permian (then so named by myself) inclusive. This was no “ downward development,” but an original and clear exposition of a true, natural ascending order from a fossiliferous base-line. This being done, and the North American geologists having adopted the same views, it still remained a desideratum in our own country to ascertain, by physical and geological proofs, if the Cambria of Sedgwick was what I had suggested, i. e. essentially nothing but Lower Silurian. In North Wales Mr. Davis made the first approach to the ascer- tainment of a base of what he termed “Silurian Rocks,” by the discovery (November 1845) of the now well-known Lingula-beds of Tremadocf, the true physical position of which, in reference to the underlying unfossiliferous grits of Barmouth and to the overlying series replete with common Lower Silurian fossils, was subsequently carried out by Professor Sedgwick and the Government Geological surveyors. (1846.) In all his publications in the Proceedings and the Journal of the Society, up to the early part of 1846, Professor Sedgwick made no objections to the sense which I had so prominently attached to the term “Silurian” in 1841, 1842, and 1843. He had then even himself so applied my nomenclature to the rocks of Cumberland and Wales, that Mr. Horner, as President of the Society, after a full exposition of the extension of the original Siluria, thus spoke in his Anniversary Discourse of 1846% :—“Since the discovery of the Silurian key, he [Professor Sedgwick] has been enabled to make a clear and intelligible outline of the history of these regions, which, for a long time, geologists seemed to shrink from all attempts to un- derstand.” In truth, Prof. Sedgwick himself had up to that time invariably appealed to my Lower Silurian as well as to my Upper Silurian division and their respective fossils as his guides in elaborating the fossil groups of Cumberland and Wales. How, therefore, could I, or * Proceed. Gcol. Soc. vol. iv. p. 74 ; the same opinion was previously expressed (1842) vol. iii. p. 549. f Quart. Journ. Geol. Soc. vol. ii. p. 70. f Ibid. vol. ii. p. 162.