COMPOSITION AND USE OF MINERALS.
695
feet, when a very valuable seam of coal was arrived at; duringthe ten years employed in sinking this pit upwards of 100,000/.were expended.
In Staffordshire the coal is drawn out by means of anumber of pits, which are not required to be of great depth."When the shaft is first sunk, two galleries are driven, onein an horizontal line along the strike of the coal seam, theother on the rise of the bed, at right angles to it. Thefirst is termed the drift or watercourse, and the other thewinning headway, through which the coal is brought to theshaft to be hauled up : these cuttings are 9 or 10 feet in width.6 feet in height, and are made convenient for the passage ofthe waggons, which in some cases run upon rail or tramroads.After the drift and winning headway are completed, other gal-leries, varying in dimension, arc set out parallel to the latter ;some are $ or 10 feet in width, intersected by others at rightangles, the pillars of coal which are left between the galleriesfor the purpose of support being generally 8 or 9 yards in thick-ness ; and in the old method of mining these pillars were left, butsince panel work was introduced, fifty years ago, they have beenextracted: this is performed by dividing the entire mine intopanels, separated by walls of coal from 40 to 50 yards in thick-ness, and then extracting the coal from each in succession, com-mencing work in that most distant from the shaft, shutting off allcommunication with the others till the whole panel is workedout. Pillars about 24 yards by 12 are at first left between theboards, as the largest galleries are called, and the transverse gal-leries or rooms, and when the first are completed the minersattack the pillars ; the roof being supported by posts of Scotchfir, which arc removed as the work proceeds, and the roof is thensuffered to fall in. Thus the whole of the coal is now removed,and by allowing the galleries to be filled up, all danger from anaccumulation of the noxious gases is prevented.
The tools used by the collier are a mattock having both endsof the head pointed, and several kinds of chisels, crow-bars, andhammers. The coal is generally blasted, and then broken up intosmall masses ; the blasting is effected by piercing the lower partof the seam with a hole about 1 inch in diameter and 3 feet indepth, into which the cartridges are introduced, and the hole isplugged up with coal dust; the men who obtain the coal arecalled hewers, and those who load the waggons or corves theputters, who also conduct the horses to the bottom of the shaft,where the coal is drawn up.
In the Dudley coal field, where the thickness of the seam is asmuch as 30 or 40 feet, it is worked in chambers, which are calledsides of work.
The strata of coal in England usually lie horizontal; in Wales and in Scotland they are inclined, sometimes at a considerableangle; where this is found to be from 45° to 60°, as in Pembroke-shire, the mine is worked by an adit level, which passes out on ahill side. Windlasses placed along the inclined vein draw up thecoal after it has been extracted from the stalls; two sets ofcarts are used for the purpose, so attached to the windlasses thatthose which are full draw up the empty.
The whim for raising coals from the shaft is now generallyworked by a steam-engine, which gives motion to a hollowwinds that brings up the materials.
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Fig. 593.
WHIM FOB RAISING COAL.
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Fig. 592.