A carbonaceous substance lying in strata at various depths beneath the surface of the earth, and extensively used for fuel. The varieties of coal are scientifically described by Dr. Jamieson in his geological work, and classed in several species and subspecies; but, in a practical point of view, they may be divided into three classes, according to their degree of inflammability. The least inflammable kind is the anthracite, or stone coal, of which class is the Welsh and Kilkenny coal. It requires a considerable degree of heat to ignite it, but when once kindled it remains in distinct pieces in the fire without caking, producing neither smoke nor flame, making no cinder, but leaving a stony slag behind. It is chiefly used in malt kilns, dye-houses, etc. Open burning coal kindles quickly, makes a hot pleasant fire, but is soon consumed, and produces smoke and flame in abundance; it lies open in the fire, and does not cake together to form cinders, its surface being burnt to ashes before it is thoroughly calcined in the middle.
Of this kind is Cannel coal, jet, and most of the Staffordshire and Scotch coals.
Close burning coal kindles quickly, makes a very hot fire, melts and runs together like bitumen; it makes a more durable fire than any other kind of coal, and burns finally to ashes of a brownish colour. Of this kind are the Newcastle coals, and those of the surrounding districts. The various kinds of coal are often found mixed with each other, and at times some of the finer sorts run like veins between the coarser sorts.