We have been hitherto considering fossil coal as formed of the impalpable parts of inflammable bodies, united together by pressure, and made to approach in various degrees to the nature of a chemical coal, by means of subterranean heat; because, from the examination of those strata, many of them have evidently been formed in this manner.  But vegetable bodies macerated in water, and then consolidated by compression, form a substance of the same kind, almost undistinguishable from some species of fossil coal.  We have an example of this in our turf pits or peat mosses; when this vegetable substance has been compressed under a great load of earth, which sometimes happens, it is much consolidated, and hardens, by drying, into a black body, not afterwards dilutable or penetrated by water, and almost undistinguishable in burning from mineralised bodies of the same kind.

Also, when fossil wood has been condensed by compression and changed by the operation of heat, as it is frequently found in argillaceous strata, particularly in the aluminous rock upon the coast of Yorkshire, it becomes a jet almost undistinguishable from some species of fossil coal.

There cannot therefore be a doubt, that if this vegetable substance, which is formed by the collection of wood and plants in water upon the surface of the earth, were to be found in the place of fossil coal, and to undergo the mineral operations of the globe, it must at least augment the quantity of those strata, though it should not form distinct strata by itself.

It may perhaps be thought that vegetable bodies and their impalpable parts are things too far distant in the scale of magnitude to be supposed as subsiding together in the ocean; and this would certainly be a just observation with regard to any other species of bodies:  But the nature of vegetable bodies is to be floatant in water; so that we may suppose them carried at any distance from the shore; consequently, the size of the body here makes no difference with regard to the place or order in which these are to be deposited.

The examination of fossil coal fully confirms those reasonable suppositions.  For, first, The strata that attend coal, whether the sandstone or the argillaceous strata, commonly, almost universally, abound with the most distinct evidence of vegetable substances; this is the impressions of plants which are found in their composition. Secondly, There is much fossil coal, particularly that termed in England clod coal, and employed in the iron foundry, that shows abundance of vegetable bodies in its composition.  The strata of this coal have many horizontal interstices, at which the more solid shining coal is easily separated; here the fibrous structure of the compressed vegetable bodies is extremely visible; and thus no manner of doubt remains, that at least a part of this coal had been composed of the vegetable bodies themselves, whatever may have been the origin of the more compact parts where nothing is to be distinguished.