found in a confiderable quantity, of a cheerful
colour, inclining to the brown red, and
full of large marine figures in all directions,
which on being cut appear white, and afford
a pleating contraft. This beautiful
marble is ufed for chimney pieces, and
other ornaments. Near Wetton, a variety
is found, of a darker colour, and prefenting
very fmall figures, whence it is called bird’s
eye marble.
In various parts black marble is found in
laminse, being coloured by iron and petroleum,
which is frequently found to pervade
the mafs. It burns to a white lime, which
forms a ftong cement. All the varieties are
foetid when rubbed with a harder fubftance.
The coralloids that are found in the black
marble have a very pretty ftarry or ftellated
appearance, but fuch pieces are not common.
A filiceous fubftance called chert, ufed
by
by the potters, is found in the limeftone
ftratum, in large detached malfes and thin
ftrata, near Caftleton, at Dirtlow, at Brad-
well, in Middleton dale, in Peak foreft,
Matlock, and various other places. This
fubftance is full of marine figures, and animal
remains ; in which refpeCt it refembles
the limeftone, as though it had undergone
a tranfition into petrofilex, or what the
French call keralite. I have fpecimens,
partly filiceous, and partly calcareous. The
ftiells in this fubftance, and in the limeftone,
are full of calcareous cryftallizations, and
fometimes contain bitumen.
In this large calcareous ftratum are many
caverns, particularly that wonderful work
of nature, Peak’s Hole.
The limeftone in the Peak foreft is the
beft: the frafture fcaly bright; it is compact;
and fonorous when ftruck. It burns to a
fine white lime, lofing about thirty per cent.
of