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 fuliginous substance as might suffice for the formation of bituminous strata, no difficulty would be left in explaining the original of fossil coal.  But tho’ sufficient quantity of this fuliginous matter might not be found for the explanation of natural appearances, yet there cannot be a doubt that more or less of this matter must be produced in the mineral operations of the globe, and be found precisely in that place where it is required for the forming of those strata of coal.

In order to conceive this, we are to consider, that there are actually great quantities of coal strata in a charred state, which indicates that all their more volatile oleaginous or fuliginous matter had been separated by force of subterranean heat; and, we are to suppose that this had been transacted at the bottom of the ocean:  Consequently, a subtile oleaginous, bituminous, or fuliginous substance, must have been diffused in that ocean; and this bituminous matter would be employed in forming other strata, which were then deposited at the bottom of the waters.

But besides this quantity of bituminous matter which is necessarily formed in the mineral operations of the earth, and with regard to the quantity of which we can never form a proper estimate, there must enter into this same calculation all the fuliginous matter that is formed in burning bodies upon the surface of this earth.  This bituminous matter of smoke is first delivered into the atmosphere, but ultimately it must be settled at the bottom of the sea.  Hence though, compared with the quantity that we think required, each revolution of the globe produces but a little in our estimation, yet the progress of time, in reforming worlds, may produce all that is necessary in the formation of our strata.

There now remains to explain the other way in which bituminous matter may be obtained from vegetable bodies, that is, by means of water.  For this purpose we must begin with a part of natural history that will throw some light upon the subject.

All the rivers in Scotland run into the sea tinged with a brown substance; this is most evident in some of them after a flood, and while yet the river is swelled; but, in travelling to the north of Scotland in the summer season, without any rain, I saw all the rivers, without exception, of a brown colour, compared with a river of more clear water.  This colour proceeds from the moss water, as it is called, which runs into the rivers, or the infusion of that vegetable substance which forms combustible turf, called peat.  Now, this moss water leaves, upon evaporation, a bituminous substance, which very much resembles fossil coal.  Therefore, in order to employ this vegetable infusion, delivered into the ocean for the purpose of forming bituminous strata at its bottom, it is only required to make this bituminous matter separate and subside.