Siluria : a history of the oldest rocks in the British Isles and other countries with sketches of the origin and distribution of native gold, the general succession of geological formations, and changes of the earth's surface / by Sir Roderick Impey Murchison.

Roderick Murchison, 1st Baronet

Date:: 1867

Credit: Siluria : a history of the oldest rocks in the British Isles and other countries with sketches of the origin and distribution of native gold, the general succession of geological formations, and changes of the earth's surface / by Sir Roderick Impey Murchison. Source: Wellcome Collection.

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$upper deposits, I then began to classify these rocks. After four years of consecutive labour, during which I received much valuable assistance from the Eev. T. Lewis, of Aymestry, and Dr. Lloyd, of Ludlow, and exhibiting each year fossil evidences before the Geological Society to 2)rove the inde- pendence and succession of the strata, I assigned to them (in 1835) the name Silurian,” deriving it from the portion of England and AVales in wdiich the successive formations are clearly displayed, and wherein an ancient British people, the Silures, under their king Caradoc (Caractacus), had opposed a long and valorous resistance to the Homans. Having fii’st, in the year 1833, separated these deposits into four formations^, and shown that each is characterized by peculiar organic remains, I next divided them (1834, 1835) into a lower and an upper group, an arrangement which I hoped would be found applicable to wide regions of the earth. After seven years of labour in field and closet, the proofs of the truth of those views were more fully published in tlie large work entitled the ‘ Silurian System’ (1838-9). As the original (]uarto has long been out of print, let me put the reader in possession of some of the leading views it contains, by quoting the following passages, in which, having pre\dously described the overlying deposits, the lowest of which is the Old Hed Sand- stone (since termed Devonian), I thus ushered in the new classification ;— We have at length reached those older deposits, which, not having been separated into formations by preHous writers, I am compelled to de- scribe under new terms. Acting upon the principle that guided William Smith in subdividing the Oolitic system of our island, I have named these rocks from places in England and Wales where their succession and age are best proved by order of superposition and imbedded organic remains, and have termed them in descending order, the ‘ Ludlow,’ ‘ Wenlock,’ ‘ Caradoc,’ and ^ Llandeilo’ 'formations. The same principle has led me to use the general term of ^ Silurian System’ for the group, to mark thereby the territory in which the best types and the clearest relations are exhibited^ “ Like every other mass of strata entitled to the name of System, the Silurian, though clearly recognizable as a whole over extensive tracts, cannot always be subdivided into those formations wliich are dis- played in the regions where I shall first describe it, and where its types are fully developed. Thus, for example, where the subordinate limestones thin out and disappear, the Ludlow deposit can seldom be elearly sepa- rated from that of Wenlock. In such cases both these formations are included in the term of ‘ Upper Silurian Hocks,’ and, under similar cir- * For the first tabular view of these four for- mations, the lower one resting on the then so- called ‘ unfossiliferous greywacke ’ (afterwards named ‘ Cambrian') of the Longmynd, see Pro- ceedings Geol. Soc. Lond. vol. ii. p. 11, Jan. 18:J4. The chief characteristic fossil species were even then enumerated, and specimens placed in the Museum of the Geological Society; and hence the classification which is now sustained is essentially thirty-two years old. It liad even been previously stated by me (in 18JJ) that the lowest fossil-bear- ing formation then known to me, or the ‘ black trilobite flagstone’ of Llandeilo, probably ex- ceeded in thickness any of the superior groups (Proc. Geol. Soc. vol. i.p. 170).$