MINING FOK COAL 



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pavement and the roof, within a few feet of each other (as ehown by the dots), till an 

 area of above 100 yards square is cleared of pillars, presenting a body of strata per- 

 haps 130 fathoms thick, suspended clear and without support, except at the line of 

 the surrounding pillars. This operation is termed working the goaf. The only use 

 of the prop-wood is to prevent the stratum, which forms the ceiling OA'er the workmen's 

 heads, from falling down and killing them by its splintery fragments ; Experience 

 has proved that before proceeding to take away another set of pillars, it is necessary 

 to allow the last-made goaf to fall. The workmen then begin to draw out the props, 

 which is a most hazardous employment. They begin at the more remote props, and 

 knock them down one after another, retreating quickly under the protection of the 

 remaining props. Meanwhile the roof-stratum begins to break by the sides of the 



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pillars, and falls down in immense pieces ; while the workmen still persevere, boldly 

 drawing and retreating till every prop is removed. Nay, should any props be so firmly 

 fixed by the top pressure that they will not give way to the blows of heavy mauls, 

 they are cut through with axes ; the workmen making a point of honour to leave not 

 a single prop in the goaf. If any props arc left in the goaf it causes an irregular 

 subsidence of the strata, and throws more pressure on the adjacent pillars. The 

 miners next proceed to cut away the pillars nearest to the sides of the goaf, setting 

 prop-wood, then drawing it, and retiring as before, until every panel is removed, 

 excepting small portions of pillars which require to be left under dangerous stones to 

 protect the retreat of the workmen. "While this operation is going forward, and the 

 goaf extending, the superincumbent strata, being exposed without support over a 

 large area, break progressively higher up ; and when strong beds of sandstone are 

 thus giving way, the noise of the rending rocks is very peculiar and terrific ; at one 

 time loud and sharp, at another hollow and deep. 



As the pillars of the panels are taken away, the panel-walls are also worked pro- 

 gressively backwards to the pit-bottom ; so that only a very small proportion of coal 

 is eventually lost. 



The fourth system of working coal is called the long way, the long-wall, or the 

 Shropshire and Derbyshire method. 



The object of this system is, to begin at the pit-bottom, and to cut away at once 

 every inch of coal progressively forward, and to allow the whole superincumbent 

 strata to crush down behind and over the heads of the workmen. This plan is 

 pursued chiefly with coals that are thin, from 4 to 5 feet being reckoned the most 

 favourable thickness for proceeding with comfort, amidst ordinary circumstances, as 

 to roof, pavement, &c. When a pit is opened on a coal to be treated by this method, 

 the position of the coals above the lowest seam sunk to must first be considered ; if 

 the coal-beds be contiguous it will be proper to work the upper one first, and the rest 

 in succession downwards ; but if they are 8 fathoms or more apart, with strata of strong 

 texture betwixt them, the working of the lower coals in the first place will do no injury 

 to that of the upper coals, except breaking them, perhaps, a little. In many instances, 

 indeed, by this operation on a lower coal, upper coals are rendered more easily worked. 



