Murchison’s Siluria. 399 
lations aa contents of all the inferior strata undefined, but even 
many rocks which are now known to be younger than the Silu- 
rian, seo pe considered to be of much more remote antiquity. 
No one had then surmised, that the great series of hard slates 
with limestones and fossils, which have since been termed Devo- 
nian, is an equivalent of the Old Red Sandstone, and youngér 
than, as well as distinct from, the deposits of the still older Siln- 
rian era. On the contrary, British authorities believed (and I 
was myself so taught) that the schistose and subcrystalline sora 
of Devonshire and Cornwall were about the most ancient of t 
vast undigested heaps of greywacke. In ni the best sobre 
gists* of my early days were accustomed to leave off with such 
rocks, as constituting obscure heaps of sediment, in and below 
which no succession of “strata as identified by their fossils” 
could be detected. The result of research, however, has been 
the elimination of several well-defined groups, all of which were 
formerly merged in the nismnenineea German term ‘“ grauwacke.”’ 
(See Chapter 14. 
Desirous of throwing light on this dark subject, I consulted 
my valued friend and instructor, Dr. Buckland, as to the region 
most likely to afford evidences of order, and by his advice [ first 
explored, in 1831, the banks of the Wye between Hay and 
Builth. Discovering a considerable tract in Hereford, Radnor 
and Shropshire, wherein large masses of grey-colored strata rise 
out from beneath the Old Red Sandstone, and contain fossils dif- 
peop ie the Silures, under their king Caradoc Onrentncas> had 
opposed a long and valorous resistance to the Romans. Having 
first, in the year 1833, separated these deposits} into four forma- 
tions, and shown that each is characterized by peculiar organic 
remains, I next divided them (1834, 1835) into a lower and up- 
Per group, both of which I hoped would be found applicable to 
wide regions of the earth. After eight years of labor in the field 
and closet, the proofs of the truth of those views were more fully 
published in the work entitled the “Silurian System” (1839). 
_ * See those classical works, the first Geological Ben sh Mr. Greenongh, and the 
Geology of England and Wales, by the Rev. W. D. Cony 
nt oot the first tabular view of tt ese four ssesanticas che Wolleat aak vhcoagon 
unfossili 
; Pe server any of the superior gr —Proc, Geol. Soc., vol. i, p. 476, 1833. 
