Caithness; and in Russia and North America, if not in many other
parts of the world. The particular strata forming the system are
somewhat different in different countries; but there is a general
character to the extent of these being a mixture of flagstones, marly
rocks, and sandstones, usually of a laminous structure, with
conglomerates. There is also a schist shewing the presence of
bitumen; a remarkable new ingredient, since it is a vegetable
production. In the conglomerates, of great extent and thickness,
which form, in at least one district, the basis or leading feature of
the system, inclosing water-worn fragments of quartz and other rocks,
we have evidence of the seas of that period having been subjected to
a violent and long-continued agitation, probably from volcanic
causes. The upper members of the series bear the appearance of
having been deposited in comparatively tranquil seas. The English
specimens of this system shew a remarkable freedom from those
disturbances which result in the interjection of trap; and they are
thus defective in mineral ores. In some parts of England the old red
sandstone system has been stated as 10,000 feet in thickness.

In this era, the forms of life which existed in the Silurian are
continued: we have the same orders of marine creatures, zoophyta,
polypiaria, conchifera, crustacea; but to these are added numerous
fishes, some of which are of most extraordinary and surprising forms.
Several of the strata are crowded with remains of fish, shewing that
the seas in which those beds were deposited had swarmed with that
class of inhabitants. The investigation of this system is recent;
but already {68} M. Agassiz has ascertained about twenty genera, and
thrice the number of species. And it is remarkable that the Silurian
fishes are here only represented in genera; the whole of the SPECIES
of that era had already passed away. Even throughout the sub-groups