flourifti, the arts and manufactures would
be extended; and from its appearance might
be dated the riches of that country.
Coal is frequently found under a'variety
of fubftances, commonly appearing in the
form of ftrata, and called by the colliers
under-foil, gravely bind, clutch, hardfone,
metal, plate, Sec. as has been before mentioned,
which are fometimes only a few
inches thick, in others feveral feet ; but
generally the grit is fuperincumberit.
No. 2. (fee plate i.) The ftratum of
coarfe filiceous grit, extending at the moft
about 120 yards, and variable in its appearance
and texture. It forms the uppermoft
ftratum in Wirkfworth Moor, Cromford
Moor near Winfter, the Eaft Moor, Birch-
over, Matlock town, the Edge fide Hills,
from Earn to Caftleton, of Mam Tor, and
in many other places.
It is an aflemblage of coarfe quartzy
pebbles
pebbles of various fizes, feldom exceeding a
quarter of an inch diameter; fome are in
part cryftalized: with {harp angles, others
are rounded.; it is very friable near the fur-
face, and fometimes contains adventitious
matter: it is not {{ratified. It gives fire
with fteel; refifts acids; and is often coloured
by iron: fradure irregular, and does not
take a polifh., In this ftratum are varieties
of grit ftone in laminae ; fome are called
freeftone, and ufed in buildings; others
called millftone grit, and ufed for millftones.
A particular variety is laminated with mica,
being an excellent fubftitute for flatej and
ufed in forming the roofs of buildings,
whence it is an article of commerce. This
variety is fomewhat elaftie, and eafily divides
with a knife. Frequently it contains
cryftallized fluor, and barytes, and is incumbent
on fhiftus or {hale, from which it
is feparated by a thin feam of clay.
f 4 In