n the waters of the ocean, and subsided _pari
passu_ with the proper materials of the coal, we hence learn a great
deal with regard to the state in which the inflammable matter must have
been at the time of its formation into strata. This will appear by
considering, that we find schistus mixed with coal in the most equal or
uniform manner, and in almost every conceivable degree, from the purest
coal to the most perfect schistus. Hence we have reason to conclude,
that, at the formation of those strata, the bituminous matter, highly
subtilised, had been uniformly mixed with the earth subsiding in the
water.

Not only is the bituminous matter of coal found mixed in every different
proportion with the earthy or uninflammable materials of strata, but the
coaly or bituminous composition is found with perhaps every different
species of substance belonging to strata. This is certain, that we have
the coaly matter intimately mixed with argillaceous and with calcareous
strata.

Thus it will appear, that it is no proper explanation of the formation
of coal strata, to say that vegetable matter is the basis of those
strata; for though, in vegetation, a substance proper for the formation
of bituminous matter is produced, it remains to know by what means, from
a vegetable body, this bituminous matter is produced, and how it comes
to be diffused in that subtile state by which it may be uniformly mixed
with the most impalpable earth in water. Could we once resolve this
question, every other appearance might be easily explained. Let us
therefore now endeavour to discover a principle for the resolving of
this problem.

There are two ways in which vegetable bodies may be, in part at least,
resolved into that subtilised state of bituminous matter after which we
inquire; the one of these is by means of fire, the other by water. We
shall now consider these severally as the means of forming bituminous
strata, although they may be both employed by nature in this work.

When vegetable bodies are made to burn, there is always more or less of
a fuliginous substance formed; but this fuliginous substance is no
other than a bituminous body in that subtilised state in which it is
indefinitely divided, and may be mixed uniformly with any mass of matter
equally subtilised with itself. But this is precisely what we want, in
order to compose the strata of coal in question. If, therefore, there
were to be found in the ocean such a fund of this fuligino