854 



MINE. 



Mince of 

 Coal. 



press down and rest upon the gob ; for if, in this case, 

 small pillars of coal were left in the working in place of 

 ' ; pillars, or the props set very firm, the consequence 

 coal. would be, that the instant the least pressure came for- 



ward, the coal pillars would fly to pieces, every prop 

 would be instantly broken, the roof come down, and 

 the workmen be killed ; whereas, by the pillars and 

 props yielding gradually, until the gobbing receives 

 the pressure, all points are kept right, and the props 

 are- saved for farther service. In Shropshire, some 

 collieries use a great proportion of cast-iron props. 

 This plan is a saving, when an iron work is connect- 

 ed with the colliery, that when a prop breaks it is recast 

 at little expence, but in ordinary cases the expence will 

 be found too great. When props will not drive out by 

 applying the force of heavy mauls, a long chain with a 

 hook is provided, the hook is fixed to the bottom or 

 top of the prop, and the other end, having a small hook, 

 is doubled up to form an eye or loop, which is passed 

 over a strong lever of iron or wood, the point of which 

 resting against a firm prop, gives the workmen great 

 power in wrenching the other prop from its place. 



Another modification of the Shropshire method, is 

 for each workman to have from 6 to 12 feet of coal be- 

 fore him, with a leading hand man, and where every 

 workman follows in succession like the steps of a stair. 

 If the coal has open backs and cutters, this work goes 

 PLATE on very regularly, as represented in Fig. 3, Plate 

 cccxcii. CCCXCII. where the leading hand is at a, next the 

 ftg. S. crap, and b, b, &c. are the wall faces of each work- 

 man, A the pit, B the dip-head level. In this case the 

 roads are either carried progressively through the gob, 

 or the gob is altogether shut up, and the whole of the 

 coals are brought down the wall-faces, either to the 

 dip-head level or to the road c c. This method may be 

 varied by making the walls of a breadth to hold two, 

 three, or four men ; by this plan each set of men per- 

 forms the whole work of holing, getting, breaking 

 out, and carrying away the coals. This mode can be 

 also equally wellj adopted by working the coals level- 

 course with the leading hand next the dip-head. 



It may be estimated, that from an eighth to a twelfth 

 part only of the coal is left under ground by the Shrop- 

 shire system, and in favourable instances every inch of 

 coal can be taken out, the principle being to leave no 

 solid pillars, or any coal below, excepting what may 

 be inclispensibly requisite to secure the gob. This 

 system might be applied to coals of almost any thick- 

 ness, providing stuff could be got to fill up the gob. 

 It is the want of it which limits this system to coals 

 of a certain height. Various modifications of the sys- 

 tems now described are in use, but it would be endless 

 to describe them ; the general principles are the same ; 

 The object and intention being always to produce as much 

 coal as possible from a given, area, as may be consist- 

 ait ti'ilk the safety of the workmen, having all other cir- 

 cumstances as before mentioned in view. 



Such being the general modes practised in Great 

 Britain, of working coals of ordinary thickness and of 

 moderate dip and rise, a general description will now 

 be given of the methods pursued in working coals of 

 the following description : 



1. Very thin coals. 



2. Very thick coals. 



3. Coals having a great dip and rise, or what are 

 termed edge coals. 



Tbin coals. Beds of coal in Great Britain are wrought as thin as 

 IS inches as a coal mine; if wrought thinner the 

 working of fire-clay or iron-stone immediately ad- 



joining is connected with them. There are, however, Mines of 

 instances of caking coals, of a fine quality for smiths, Co * 1 - 

 being wrought alone, only 12 inches in thickness. 

 When the bed is 18 inches in thickness, it can be 

 wrought by men of the ordinary size, but young men. 

 and boys are more suitable. Coal of this thickness can 

 be wrought without lifting the pavement, or taking 

 down the roof in the rooms ; but for taking out the 

 coals, roads are cut either in the pavement or roof. 

 All coals under two feet three inches in thickness are 

 wrought with the intention of taking out all the coal, 

 either in the Shropshire system, or with pillar-walls 

 and rooms ; with this difference, that from the thin, 

 ness of the bed the rooms are wrought as wide as the 

 roof will carry up, or if a following or fall of the root, 

 stone can be brought on, it is an advantage, as it not 

 only gives height, but, by filling up the waste, renders 

 the roads easily kept for the working of the pillars. 

 Where there is no following, small temporary pillars 

 are left, about eight feet square, along the chain-wall 

 side. The walls are from four to sixteen yards in 

 thickness, according to circumstances, and only holed 

 through occasionally for air. The rooms 20 feet in 

 breadth, with the small pillars set six or eight feet 

 from the pillar side or chain- wall, and eight feet apart 

 from each other. When the workings are carried to 

 the required extent, the chains of wall and small pil- 

 lars are begun to be wrought at the most distant point, 

 and finished off at the pit-bottom. Of this method 

 there are also various modifications, depending upon 

 the texture of the coal, the kind of roof, pavement, 

 and superincumbent strata. The common post and 

 stall work is not suitable for such thin coals, particu- 

 larly as a given area yields so small a quantity of 

 coals. 



Coals which are from five to eight feet in thickness, 

 are the most suitable in every point of view for the 

 full effective exertion of the miner, and for the general 

 economy of under-ground operations. When they 

 much exceed this height, they require very excellent 

 roofs and pavements, to render the work safe and com- 

 fortable, or to enable those who direct the mining 

 operations to take out a fair proportion of coal from a 

 given area. In these thick coals the Shropshire me- 

 thod is impracticable for want of gobbing, and the 

 length of the props would present but a feeble resist- 

 ance to the pressure of heavy roof stones. 



When coals do not exceed 20 feet in thickness, nnd Thick 

 have good roofs, they are sometimes wrought as one coals, 

 bed of coal ; but if the coal is tender or free, it is 

 wrought as two beds. In general, however, nearly a 

 half of the coal is lost in pillars, and very seldom can 

 less than a third be left. In working such a coal as 

 one bed, two modes are adopted. 



The first is, to work the roof-coal to the thickness of 

 from four to six feet, the length of a pillar and thirling, 

 and four feet more; then the ground coal is wrought 

 as a bench under foot by the partings, as an open cast 

 quarry above ground ; but before the ground-coal is 

 taken down opposite the thirling, the thirling is set in 

 four feet in the roof-coal, and then the whole of the 

 ground-coal is wrought away ; this leaves a bench or 

 seat of four feet broad in the forehead of the room, 

 and in the mouth of the thirling, for the collier to 

 stand on when he commences to work the roof-coal 

 either in the room or thirling. Without leaving this 

 bench, a scaffolding of timber would require to be 

 erected for commencing his operations again. 



The other method is to work a portion of the 



