things from their original to the place in which
they had been ultimately deposited at the bottom of the sea. It is
enough that we find the substance of which we treat delivered into
the sea, and regularly deposited at the bottom, after having been
transported by the currents of the ocean. Now the currents of the ocean,
however regular they may be for a certain period of time, and however
long this period may be protracted, naturally change; and then the
currents, which had given birth to one species of stratum in one place,
will carry it to another; and the sediment which the moment before
had formed a coal stratum, or a bed of that bituminous matter, may
be succeeded either with the sediment of an argillaceous stratum, or
covered over with a bed of sand, brought by the changed current of the
sea.

We have now considered all the appearances of coal strata, so far as
these depend upon the materials, and their original collection. But,
as those bituminous strata have been changed in their substance by the
operation of subterranean heat and inspissation, we are now to look for
the necessary consequences of this change in the body of the stratum;
and also for other mineral operations common to fossil coal with
consolidated strata of whatever species.

If coal, like other mineral strata, have been inspissated and
consolidated by subterranean heat, we should find them traversed with
veins and fissures; and, if the matter found in those veins and fissures
corresponds to that found in similar places of other strata, every
confirmation will be hence given to the theory that can be expected from
the consideration of those bituminous strata. But this is the case; we
find those fissures filled both with calcareous, gypseous, and pyritous
substances. Therefore, we have reason to conclude, that the strata of
fossil coal, like every other indurated or consolidated body in the
earth, has been produced, _first_, by means of water preparing and
collecting materials proper for the construction of land; and,
_secondly_, by the operation of internal fire or subterranean heat
melting and thus consolidating every known substance of the globe.

Not only are those sparry and pyritous substances, which are more
natural to coal strata, found forming veins traversing those strata in
various directions, but also every other mineral vein may occasionally
be found pervading coal mines, or traversing bituminous strata. Gold,
silver, copper, lead,