Coal is a vegetable that, by _chemical change_ and by _mechanical pressure_, has become a bituminous mineral; and this will render it needful to say a word or two on the ancient vegetable kingdom. The vast quantities[56] of remains of leaves, ferns, and stems of trees, found in the coal measures, are not in themselves evidence sufficient of the vegetable origin of coal; we arrive at that conclusion in consequence of the researches of modern philosophers, who having applied the powers of the microscope to the internal structure of coal, have discovered the cellular and reticular construction of vegetable life beautifully preserved, and thus previous convictions have become certainties. The examination of the ancient vegetable kingdom is, however, attended with much difficulty, in consequence of the total destruction in most cases of the stems and trunks of the plants, and the entire absence, in consequence of pressure, of all fructification on the fronds of the ferns. If we take an existing species of fern, say the rare and delicate “maiden-hair fern,”[57] one of the smallest and most elegant ferns of England, we find the fructification very distinct on the under side, and the different methods in which this fructification is arranged is now the principal guide in the classification of ferns. But if we take a fossil fern, say the pecopteris, found in the coal measures, we shall see that there has been so much dislocation and crushing, that all appearance of seed-vessels has disappeared. The following sketch will explain this. [Illustration: EXTINCT FERN, AND MAIDEN-HAIR FERN. ] “Nothing,” says Professor Ansted, “however, is more certain than that all coal was once vegetable; for in most cases the woody structure may be detected under the microscope, and this, if not in the coal in its ordinary state, at least in the burnt ashes which remain after it has been exposed to the action of heat, and has lost its bituminous and semi-crystalline character. This has been too well and too frequently proved by actual experiment to require more than the mere statement of the fact.” And here let us say a few words, which to a few perhaps may have the charm of novelty, about the economic history of coal; for as Cowper says that the first curse, “labour,” has, by God’s blessing on it, been “softened into mercy,” so do we add also, in his words, heartily subscribing to their truth,— “Thus studied, used, and consecrated thus, On earth what is, seems formed indeed for us; Not as the plaything of a froward child, Fretful unless diverted and beguiled; But as scale, by which the soul ascends From mighty means to more important ends; Securely, though by steps but rarely trod, Mounts from inferior beings up to God; And sees, by no fallacious light or dim, Earth made for man, and man himself for Him.”