Chap. I.] 
THE SILURIAN SYSTEM ESTABLISHED. 
5 
upper deposits, I then began to classify these rocks. After four years of 
consecutive labour, during which I received much valuable assistance from 
the Rev. T. Lewis, of Aymestry, and Dr. Lloyd, of Ludlow, and exhibiting 
each year fossil evidences before the Geological Society to prove 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 Wales in which 
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 Eomans. Having first, 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 the large work entitled the 
' Silurian System' (1838-9). As the original quarto 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 previously 
described the overlying deposits, the lowest of which is the Old Red 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 previous 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 which 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 clearly sepa- 
rated from that of Wenlock. In such cases both these formations are 
included in the term of ' Upper Silurian Rocks,' and, under similar cir- 
* For the first tabular view of these four for- classification which is now sustained is essentially 
mations, the lower one resting on the then so- thirty-two years old. It had even been previously 
called ' unfossiliferous greywacke ' (afterwards stated by me (in 1833) that the lowest fossil-bear- 
named » Cambrian ') of the Longmynd, see Pro- ing formation then known to me, or the 'black 
ceedings Geol. Soc. Lond. vol. ii. p. 11, Jan. 1834. triiobite flagstone' of Llandeilo, probably ex- 
The chief characteristic fossil species were even ceeded in thickness any of the superior groups 
then enumerated, and specimens placed in the (Proc. Geol. Soc. vol. i. p. 476). 
Museum of the Geological Society ; and hence the 
