Murchison’s Siluria. 373 
son, “Before the labors which terminated in the publication 
of the ‘Silurian System,’ no one had unravelled the detailed se- 
quence and characteristic fossils of any strata of a higher anti- 
- quity than the Old Red Sandstone ; and even that formation was 
only known to be the natural base of the carboniferous or moua- 
tain limestone, and to contain a few undescribed fossil fishes. 
Not only were the relations and contents of the inferior strata un- 
defined, but even many rocks»which are now known to be 
younger than the Silurian, were then 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 
been termed Devonian, is an equivalent of the Old Red Sand- 
stone, and younger than, as well as distinct from, the deposits of 
the still older Silurian era. On the contrary, British authorities 
believed (and I was myself so taught) that the schistose and sub- 
crystalline rocks of Devonshire and Cornwall were about the 
most ancient of the vast undigested heaps of greywacke. In 
short, the best geologists of my early days were accustomed to 
ve off with such rocks, as constituting obscure heaps of sedi- 
ment, in and below which no succession of ‘strata as identified 
by their fossils’ could be detected.’ ” 
It was in 1831 that Murchison, desirous of throwing some 
light on this dark subject, under the advice of Dr. Buckland, be- 
gan his explorations along the borders of England and Wales, 
where the older rocks are well developed. At the same time 
Prof. Sedgwick, with similar intentions, selected North Wales as 
the field of his labors, and for many years both these gentlemen 
labored indefatigably to elucidate the order of succession of the 
palezozoic strata. In 1833 and 1834, Murchison presented vari- 
ous papers containing the results of his observations to the Geo- 
logical Society of London, and ém the last named year prepared a 
classification of these ancient strata, which is essentially the same 
as the one now sustained by him, the rocks below the 
being grouped into four formations (Ludlow rocks, Wenlock and 
Dudley rocks, Horderly and May Hill rocks, afterwards named 
Caradoe, and Builth and Llandeilo flags) the whole underlaid by 
the unfossiliferous greywacke of the Longmynd. In 1835 the 
hame Silurian was given to these four groups, and the distinction 
between upper and lower Silurian was established. Eight years 
of persevering labor were at length worthily crowned by the ap- 
pearance of the magnificently illustrated quarto, entitled, “ The 
ilurian System,” which appeared i | In this work, so 
. - 
well known to every geologist, the fossils which up to that time 
ve been discovered in the Silurian groups were described and 
the most emine 
lish palzontologists, and thus 
