great impofitions and lofs. But now that
mineralogy is becoming a fafhionable ftudy,
we may expe<ft to fee great improvements
in this important branch of natural hiftory.
Let us now return to a more mintue
confideration o f the ftrata above delineated.*
No. i. Argillaceous grit forms the up-
permoft ftratum, and is more or lefs thick,
as the furface is more or lefs uneven. It is
an aflemblage of fand, and adventitious
matter, in a b^fe of argil; fradure granular j
of a dull colour; fmell earthy when breathed
on: does not effervefce with acids; does not
take a polifh ; may be eafily fcraped with a
knife; has often browniih red veins; and
is fometimes ferruginous, which renders it
heavier, By expofure to the atmofphere
it decompofes.
* Tablets, compofed of the fubftances themfelvcs, in their1
natural order, may be had of the author, forming a portable
and interefling picture of the geology of Derbyfhire.
This ftratum generally indicates iron ore,
which is frequently found under it in lamina*
and nodules. The argillaceous iron ore is
the moft common: a reprefents a thin bed
of it, of a hrown colour, and compadt nature
; fmell earthy; yields about 30 per cent,
feldom more., Nodules of this ore are frequently
found, which eafily divide, and
fhew very fine impreflions of plants, flowers,
coralloids, and (hells. The ftrata of
argillaceous grit and iron are generally incumbent
on coal, as at b, which reprefents
coal lying in lamina;, unequal in quality
and thicknefs. It frequently abounds with
pyrites or fulphuret of iron, and argillaceous
iron ore in nodules: fradlure generally
fplintery, laminated, fometimes regular, with
a bright glofs, and very brittle: contains
much fulphur and petroleum.
Coal is found at New hall, about ten
miles fouth of Derby; it is there covered