eat
Britain,' vol. iii. 1866.
(13) "On the Ancient Rocks of the St David's Promontory, South Wales,
and their Fossil Contents." Harkness and Hicks.--' Quart.
Journ. Geol. Soc.,' xxvii. 384-402. 1871.
(14) "On the Tremadoc Rocks in the Neighbourhood of St David's,
South Wales, and their Fossil Contents." Hicks.--'Quart.
Journ. Geol. Soc.,' xxix. 39-52. 1873.

In the above list, allusion has necessarily been omitted to numerous
works and memoirs on the Cambrian deposits of Sweden and Norway,
Central Europe, Russia, Spain, and various parts of North America,
as well as to a number of important papers on the British Cambrian
strata by various well-known observers. Amongst these latter
may be mentioned memoirs by Prof. Phillips, and Messrs Salter,
Hicks, Belt, Plant, Homfray, Ash, Holl, &c.

CHAPTER IX.

THE LOWER SILURIAN PERIOD.

The great system of deposits to which Sir Roderick Murchison
applied the name of "Silurian Rocks" reposes directly upon the
highest Cambrian beds, apparently without any marked unconformity,
though with a considerable change in the nature of the fossils. The
name "Silurian" was originally proposed by the eminent geologist
just alluded to for a great series of strata lying below the Old
Red Sandstone, and occupying districts in Wales and its borders
which were at one time inhabited by the "Silures," a tribe of
ancient Britons. Deposits of a corresponding age are now known
to be largely developed in other parts of England, in Scotland,
and in Ireland, in North America, in Australia, in India, in
Bohemia, Saxony, Bavaria, Russia, Sweden and Norway, Spain, and
in various other regions of less note. In some regions, as in
the neighbourhood of St Petersburg, the Silurian strata are found
not only to have preserved their original horizontality, but
also to have retained almost unaltered their primitive soft and
incoherent nature. In other regions, as in Scandinavia and many
parts of North America, similar strata, now consolidated into
shales, sandstones, and limestones, may be found resting with
a very slight inclination on still older sediments. In a great
many regions, however, the Silurian deposits are found to have
undergone more or less folding, crumpling, and dislocation,
accompanied by induration and "cleavage" of the finer and softer
sediments; whilst in some regions, as in the Highlands of Scotland,
actual "metamorphism" has taken place. In consequence of t