of the carbonic gas during the operation,
which occupies about thirty hours of a
ftrong fire. It is burnt in conical kilns of
various fizes. Irregular maffes of lime-
ftone, confiding of fragments cemented
together by infiltrated water, are fometimes
found, with crydallized calcareous fpar, &c*
in the interdices.
This ftratum is the mod intereding to
the mineralogid, for in it are found the
principal veins, containing galena, fulphu-
ret and * native oxyd of zinc, a variety of
ochres, fluors, barytes, calcareous crydalli-
zations, pyrites, &c,*
I may here be permitted to give a fhort
account of the metallic veins, as they occur
in Derbylhire. They are chiefly divided
into two varieties, rake-ox perpendicular
* The great copper mine at Efton is in this ftratum ; and
in other parts of England I have feen copper ore and iron
«res, in conftderable quantity, in the limeftone.
veins,
veins, as at R-; and pipe or dat veins as at P;
The rake veins are in different directions.
Near Cadleton they generally run from ead
to wed, and are traced, or difcovered, from
the furface. They are not exactly perpendicular
; but hade, or incline, about one
foot in ten, fometimes to the north, and
fometimes to the fouth. There are veins
that have a more northerly or foutherly
direction, and are then, called crofs veins.
Sometimes they interfeCt each other ; and.
where they unite they are generally very
rich. Small veins, ufually called Jlrings or
fcrins, often extend from the rake, and take
various directions. All are worked as lone:
as they are found profitable : and the intermediate
fubdances that divide them are
called riders, (fee r.)
The rakes generally form a drait line,
and very rarely affume a bent direction.
When feparated, "which is fometimes the
d cafe,