348 



MINE. 



coal. 



Mines of gure referred to, examples are given of the effects pro- 

 Coal, dnced upon the line of direction of the dip-head level 

 , v ~*~^ by dikes and slips, and the modes practised in passing 

 * Ork ' n 8 ' them ; but as these slips and dislocations lie in every 

 direction as to the dip and rise of the coal, there are of 

 course very various modifications of the examples given, 

 to enumerate which would be of little use, although 

 the example given appears to be a coal-field much 

 troubled, as it is termed. We have seen in practice 

 coal-fields even with more numerous dislocations. On 

 the other hand, we find coal-fields lying fair and regu- 

 lar to a very great extent. 



If, in working the coal from dip to rise, slips or dis- 

 locations of the strata occur, they are passed over in 

 several ways, according to the size of the slip. 



When the slip is only a few feet down to the rise, 

 the coal is regained at the face of the slip by an open 

 cutting like a trench, named a hassan ; but when it is 

 several yards down, and not exceeding the depth of 

 25 feet, an inclined road or mine is made down the 

 face of the slip, or at such an angle as may be most 

 suitable for bringing up the coals ; and in order to take 

 away the water, a syphon is sometimes used in place of 

 a pump, as the column of water to be raised is less 

 than the pressure of the atmosphere; for although wa- 

 ter will rise over a height of more than 25 feet by a sy- 

 phon, it runs feebly, and will not discharge much 

 water. The long end of the syphon is carried down 

 the slope of the coal towards the engine-pit, where 

 the discharging orifice is immersed in a trough of wa- 

 ter, each end is furnished with a stop-cock, and at 

 the neck or highest part of the syphon, an upright pipe 

 is attached, upon the top of which is a funnel, and a 

 stop-cock below it. These syphons were formerly 

 made of lead; but the mode of joining cast-metal pipes 

 air-tight being so effectual, syphons are now made of 

 that metal. 



When a slip is of considerable magnitude, it can be 

 levelled out by a cross-cut mine, begun sufficiently to 

 the dip. These cross-cut mines are made of a size 

 sufficient to allow the coals being brought down 

 through them to the pit bottom. When the coals are 

 very flat, and the running of cross-cut mines may not 

 be judged expedient, the coal is regained, either by 

 cutting a sloping mine, or by sinking a pit clear of the 

 rise or slope of the slip, to the coal. Sometimes the 

 water is drawn up in pumps connected with machi- 

 nery at the top of the pit, or is drawn by machinery 

 wrought by men, horses, or steam, by which means 

 the coals are also drawn. Of these plans there are 

 various modifications, according to the magnitude of 

 the slip, and its particular direction as to the dip and 

 rise of the coal. When the slip is of great magnitude, 

 it is frequently judged expedient not to attempt to 

 connect it with the established fitting, but to make a 

 new fitting for the coals on the other side of the slip, 

 the slip serving as a complete barrier betwixt the two 

 coal-fields, which in many instances is an important 

 matter to attend to, on account of the water. When 

 the slip is up to the rise, which is not a common oc- 

 currence, the operation of connecting the coals on the 

 other side of it with the main workings is very simple, 

 as there is nothing to do but updrit't a mine to the 

 coal, and then open it out to a proper width for a pit. 

 By this pit the water descends, and the coals are low- 

 ered down by a machine, with a rope-barrel regulated 

 by a brake, by which the descending loaded corve 

 draws up the empty one alternately. This mode of 



lowering coals to a lower level la very applicable in Mines of 

 many cases. 'oal. 



As soon as the crop or rise mine is run to the second 

 pit, in winning a colliery, and the dip-head levels ex- 

 tended from 30 to 80 fathoms on each side of the en- 

 gine-pit bottom, the colliery is ready for working, or 

 for producing an output of coal ; but, before proceeding, 

 an important point has to be settled, viz. the manner in 

 which the mines are to be conducted, so as to insure, 

 as far as possible, 1st, The safety of the workmen ; 

 2dly, The prosperity of the work ; and 3dly, That a 

 given area of the coal-field be made to yield the greatest 

 possible proportion of the coals contained in it. 



In the mining practice of Great Britain, there are 

 four different systems of working coal mines, viz. 



1st, Working with pillars and rooms termed post Different 

 and stall, where the pillars are left of such proportion systems of 

 to the coal excavated, as is just sufficient to support coal work- 

 the superincumbent strata. 



2rf, Working with post and stall, where the pillars 

 are left of an extra size, and stronger than is judged 

 to be requisite for supporting the strata, with the view 

 of taking away a considerable proportion of each pil- 

 lar, as soon as the regular working of post and stall is 

 completed in the colliery. 



3d, Working with post and stall, or with rooms or 

 boards comparatively narrow, and very large pillars or 

 rather walls of coal, whereby an uncommonly large 

 proportion of coal is left, having in view, that as soon 

 as the colliery is wrought to the extent of the coal- 

 field in this manner, to work back towards the pits, 

 taking away, if possible, every pillar completely, and 

 allowing the whole superincumbent strata to crush, 

 and follow the miners as they retreat. 



4//, Working the long way, or the Shropshire me- 

 thod, which is to leave no pillars, but to take out all 

 the coal progressively, as the work goes forward. In 

 this method the superincumbent strata crush down, 

 and creep very close to, and even over the heads of the 

 workmen. 



In practice the post and stall system is applied in 

 the working of coals of every thickness. The Shrop- 

 shire method, or long way, is more generally applied 

 in the working of thin coals. When the thickness ex- 

 ceeds six or seven feet, this mode of working has not 

 yet been found practicable. 



When a colliery is won in the manner as before de- 

 scribed, the next important matter to be considered, is, 

 By what plan of working the coal will that coal in 

 particular, and the coal-field in general, produce the 

 greatest quantity of vendable coals from a given area, 

 having in view all local circumstances, and also the 

 future as well as the immediate interest of the coal 

 field ? 



The local circumstances may be ranged under the Local cir- 

 following heads: cumstan- 



1st, That the lowest coal of the winning be wrought ees - 

 in such a manner as not to injure the working, or the 

 value of the upper coals w.'iich may be in the coal 

 field; but if this evidently cannot be accomplished, the 

 upper coals must be wrought first. 



2d, The texture of the coal, as to hardness or soft- 

 ness, and whether the backs and cutters are numerous 

 or not, open or close. 



3d, The kind of pavement upon which the coal 

 rests, whether it is soft or hard ; and, if soft, whether 

 it is only a few inches or several feet in thickness. 



4//, The kind of roof, whether it is good or bad ; 



