Encyclopædia Britannica, Ninth Edition/Anthracite
ANTHRACITE, Stone Coal, Kilkenny Coal, or Culm, is a variety of coal differing from the common or bituminous kind in containing a larger proportion of carbon in its composition ; that element being present in anthracite to the extent of from 90 to 95 per cent, of its entire mass, while the carbon in bituminous coal usually varies from 75 to 90 per cent. Anthracite is further distinguished by its compactness, high specific gravity, bright lustre, which is frequently iridescent on the natural surfaces, and its conchoidal fracture. It does not soil the fingers when handled, like ordinary coal ; it ignites with difficulty, and burns with a feeble, smokeless flame, giving out an intense heat. No sharply defined line of demarcation can be drawn between anthracite and the bituminous varieties of coal, as the one series merges by imperceptible degrees into the other. This gradation is observable in the coal deposits themselves, anthracite and bituminous coal being frequently found not far removed in different parts of the same seam, and the gradual transformation from a flaming coal to a compact, lustrous, non-flaming kind, being easily traceable. Anthracite has been defined as " the ultimate product of the conversion of vegetable matter into coal;" and the following table, drawn up by Dr Percy (Manual of Metallurgy], may be taken as indicating the successive stages in the process. In this table the carbon is stated at a constant standard of 1 00, in order better to exhibit the comparative quantities of the other elements which enter into the composition of the bodies named:—
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Carbon. Hydrogen. Oxygen. 1. Wood (mean of 26 analyses) 100 1218 83 07 2. Peat .1 100 9 85 55 67 3. Lignite (average of 15 varieties) 100 8 37 42 42 4. Ten Yard Coal, South Staffordshire 100 6-12 21 23 5. Steam Coal, from the Tyne 100 . 5 91 18 32 6. Peiitrefelin Coal of South Wales ...100 4 75 5 "28 7. Anthracite of Pennsylvania, U.S. ...100 2 84 174
The chief deposits of anthracite in Great Britain exist in the great coal-field of South Wales. They extend principally along the north side of the coal basin ; and on its western limit, in Pembrokeshire, the coal is entirely anthracitic. Professor Warrington Smyth remarks, on the disposition of the deposits in South Wales : " Even within the distance of a few hundred yards the Llanelly beds are seen to be bituminous where they rise to the south, and anthracitic in the opposite side of the trough." In the neighbourhood of Bideford, in North Devonshire, a series of thin seams of an impure, clayey anthracite are worked, to which properly the name culm ought to be restricted, although the whole of the anthracite exported from this country appears under that designation in the Board of Trade returns. The very meagre coal-bearing strata of Ireland yield anthracite almost exclusively. The name Kilkenny coal is given to anthracite, because that county is the centre of the South Irish coal-field, which yields no bituminous coal whatever. In the limited patches of coal found in the north of Ireland, however, some bituminous seams occur associated with anthracite. On the European continent anthracite is generally found accompanying the deposits of bituminous coal. In Belgium and Westphalia the lowest or oldest deposits of the series are anthracitic, while in Rhenish Bavaria it is the upper beds which are " dry," or least bituminous. In North America, where enormous stores of coal exist, anthracite is found in due proportion, the deposits in Pennsylvania being the richest known. The late Professor H. D. Rogers pointed out an interesting relation between the contortion or disturbance of strata in the Appalachian coal-field and the amount of bituminous matter the coal contains. In the western extension of the coal-field, where the beds are horizontal and undisturbed, the seams are highly bituminous ; and in propertion as disturbance increases, the volatile compounds decrease, till on its eastern limit, in the Appalachian chain, normous seams of a compact, pure anthracite are developed. Anthracite is used for iron-smelting and in other metallurgical operations, for lime-burning, for heating kilns, and other purposes requiring a steady, smokeless leat. As it burns with an intense concentrated heat, it is not so suitable for steam boilers as ordinary flaming coal ; and the difliculty with which it ignites, as well as its disagreeable decrepitation, renders it less eligible for household purposes.