Pit-coal exists in this island in strata, which, as far as concerns many hundred generations after us, may be pronounced inexhaustible; and is so admirably adapted, both for domestic purposes and the uses of the arts, that it is justly regarded as a most essential constituent of our national wealth. Like all other bituminous substances, it is composed of a fixed carbonaceous base or bitumen, united to more or less earthy and saline matter constituting the ashes left behind when this substance is burnt. The proportions of these parts differ considerably, in different kinds of coal; and according to the prevalency of one or other of them, so the coal is more or less combustible, and possesses the characters of perfect pit-coal; and by various shades, passes from the most inflammable canel-coal, into blind, Kilkenny, or stone-coal; and, lastly, into a variety of earthy or stony substances; which, although they are inflammable, do not merit the appellation of coal. Every body knows that when pit-coals are burning in our grates, a flame more or less luminous issues from them, and that they frequently emit beautiful streams of flame remarkably bright. But besides the flame, which is a peculiar gas in the state of combustion, heat expels from coal an aqueous vapour, loaded with several kinds of ammoniacal salts, a thick viscid fluid resembling tar, and some gases that are not of a combustible nature. The consequence of which is, that the flame of a coal-fire is continually wavering and changing, both in shape, as well as brilliance and in colour, so that what one moment gave a beautiful bright light, in the next, perhaps, is obscured by a stream of thick smoke. But if coals, instead of being suffered to burn in this way, are submitted to distillation in close vessels, all its immediate constituent parts may be collected. The bituminous part is melted out in the form of tar. There is disengaged at the same time, a large quantity of an aqueous fluid, contaminated with a portion of oil, and various ammoniacal salts. A large quantity of carburetted hidrogen, and other uninflammable gases, make their appearance, and the fixed base of the coal remains behind in the distillatory apparatus in the form of a carbonaceous substance, called coke. All these products may be separately collected in different vessels. The carburetted hidrogen, or coal-gas, may be freed from the non-inflammable gases, and afterwards forced in streams out of small appertures, which, when lighted, may serve as the flame of a candle to illuminate a room or any other place. It is thus, that from pit-coal a native production of this country, we may procure a pure, lasting, and copious light; which, in other cases, must be derived from expensive materials, in part imported from abroad.