4 
SILURIA. 
[Chap. I. 
ticable, a popular view of the oldest sedimentary rocks and of their chief 
organic remains, and thus to comprise in one octavo volume the essence of 
my own works *, as well as those of my associates, which have been pub- 
lished since the last edition of ' Siluria.' 
But before any description of these ancient deposits, as now known, is 
given, a few words are required in explanation of those researches by 
which our acquaintance with the earliest vestiges of life and order in the 
protozoic world has been attained. 
The first step which led to the present general palaeozoic classification, 
as admitted by my cotemporaries, was the establishment of the Silurian 
System of rocks and their imbedded fossils. Before the labours which 
terminated in the publication of the work so named, no one had unravelled 
the detailed sequence and characteristic fossils of any strata of a higher an- 
tiquity than the Old Red Sandstone ; and even that formation was known 
merely as the natural base of the Carboniferous or Mountain-Limestone, and 
as containing a few fossil fishes. Not only were the relations and fossil 
contents of all the lower strata undefined, but even many rocks which are 
now known to be younger than the Silurian were then considered to be 
of greater antiquity. JSTo one had then surmised that certain hard 
slates with fossiliferous limestones and sandstones, which have since 
been termed Devonian, were equivalents of the Old Red Sandstone, and 
younger than, as well as distinct from, the deposits of the still older Silu- 
rian era. On the contrary, British authorities believed (and I was myself 
so taught) that the schistose and subcrystalline rocks of Devonshire and 
Cornwall (most of which are now proved to be of the date of the Old Red 
Sandstone) were about the most ancient of the vast unclassified heaps of 
greywacke. In short, the best geologists f of my early days were accus- 
tomed to look upon all such rocks as obscure sedimentary masses, in and 
below which no succession of " strata as identified by their fossils" could 
be detected. The result of research, however, has been the development 
of several well-defined formations, all of which, even including the Lower 
Carboniferous strata, were formerly merged, in Germany, in the purely 
lithological term ' grauwackeV 
Desirous of throwing light on this dark subject, I consulted my valued 
friend and instructor, the late Dr. Buckland, as to the region most likely 
to afford evidences of order, and by his advice I first explored, in 1831, 
the banks of the Wye between Hay and Builth. Discovering in that year 
a considerable tract, in Hereford, Radnor, and Shropshire, wherein large 
masses of grey-coloured strata rise out from beneath the Old Red Sand- 
stone, and contain fossils differing from any which were known in the 
* See ' Silurian System,' Murchison, 1839 ; and t See those classical works, the first Geological 
'Russia in Europe and the Ural Mountains,' by Map of England, by W. Smith (1815), the subse- 
Murohison, de Verneuil, and de Keyserling ; J. quent map of Mr. Greenough (1819), and the 
Murray, London, 1845. Also numerous papers in Geology of England and Wales, by the Eev. W. B. 
the publications of the Geological Society of Lon- Conybeare and W. Phillips (1822). 
don from the year 1832 to 186-1. 
