Nor can metallic veins, found plentifully in "primitive" mountains, prove anything, for mineral veins are found in various strata.
We maintain that all the land was produced from fused substances elevated from the bottom of the sea. But we do not hold that all parts of the earth have undergone exactly similar and simultaneous vicissitudes; and in respect to the changes which various parts of the land have undergone we may distinguish between primary and secondary strata. Nothing is more certain than that there have been several repeated operations of the mineralising power exerted upon the strata in particular places, and all those mineral operations tend to consolidation. It is quite possible that "primitive" masses which differ from the ordinary strata of the globe have been twice subjected to mineral operations, having been first consolidated and raised as land, and then submerged in order to be again fused and elevated.
II.—The Nature of Mineral Coal
Mineral, or fossil, coal is a species of stratum distinguished by its inflammable and combustible nature. We find that it differs in respect to its purity, and also in respect to its inflammability. As is well known, some coals have almost no earthy ash, some a great deal; and, again, some coals burn with much smoke and fire, while others burn like coke. Where, then, did coal come from, and how can we account for its different species?
A substance proper for the formation of coaly matter is found in vegetable bodies. But how did it become mixed with earthy matter?
Vegetable bodies may be resolved into bituminous or coaly matter either by means of fire or by means of water. Both may be used by nature in the formation of coal.
By the force of subterranean heat vegetable matter may have been charred at the bottom of the sea, and the oleaginous, bituminous, and fuliginous substances diffused through the sea as a result of the burning may have been deposited at the bottom of the sea as coal. Further, the bituminous matter from the smoke of vegetable substances burned on land would ultimately be deposited from the atmosphere and settle at the bottom of the sea.
Many of the rivers contain in solution an immense quantity of inflammable vegetable substance, and this is carried into the sea, and precipitated there.
From these two sources, then, the sea gets bituminous material, and this material, condensed and consolidated by compression and by heat, at the bottom of the sea, would form a black body of a most uniform structure, breaking with a polished surface, and burning with more or less smoke or flame in proportion as it be distilled less or more by subterranean heat. And such a body exactly represents our purest fossil coal, which gives the most heat and leaves the least ash.
In some cases the bituminous material in suspension in the sea would be mixed more or less with argillaceous, calcareous, and other earthy substances; and these being precipitated along with the bituminous matter would form layers of impure coal with a considerable amount of ash.