XLVIII. J. HAYDON CAKDEW. 



action of the descending roof into slabs thus, see diagram F, and 

 when the face is undercut or holed the pressure of the roof added 

 to the weight of the unsupported coal tends to produce the fracture 

 of the coal along the lines of cleavage and to save labour and 

 hewing; thus enabling the produce of the seam to be obtained at 

 the least possible cost. 



In long wall working the whole of the coal is removed in a long 

 and continuous face, which is called the wall-face. A stall is that 

 portion of the wall-face kept in advance of those behind them, 

 and in which a gang of miners work. The length of the stalls 

 vary from 10 up to 50 yards, or even longer; the length depends 

 upon the strength of the coal and the roof, if the latter are strong 

 the stalls may be made long. If the face is made too long the 

 roof has a tendency to break along the line of the wall-face which 

 may become dangerous, hence it is the practice to break the line 

 of face up into stalls, one in advance of the other. 



The question of roads to the stalls is one of difficulty, and the 

 expense of keeping up numerous roads has to be avoided if possible 

 and this frequently governs the length of the stalls. The wall- 

 face may be laid out parallel to the cleat or as for the workings 

 to advance at right angles to the cleat, or the wall-face may be 

 laid out perpendicular to the cleat so that the working advances 

 on the ends, or it may be laid out as what is called "half on" or 

 with the face at 45 degrees with the cleavage planes. In the first 

 as has been shown, the mineral is "gotten" more easily and the 

 labour reduced to a minimum, and the produce of the seam is 

 obtained at the least possible cost, but if the coal is weak and 

 tender it w r ill be at a great sacrifice of physical condition and there 

 will be a great increase of waste and small coal in the getting, the 

 breaking up, and the loading. In the second method, the coal is 

 in a better position to resist the crushing effect of the descent of 

 the roof, consequently the coal will be obtained in a better con- 

 dition but at a greater cost ; therefore in strong seams it is usual 

 to lay out the wall-face parallel to the cleat for the working to 

 advance across it, and in tender seams to lay out the wall-face 



