376 



M I N E. 



Mines of 

 Coal. 



Interrup- 

 tions in 

 mining. 



Fire in the 

 mines. 



sues. Crushes are prevented by keeping the pillars 

 large; and where the roofs are bad, the boards must 

 be very narrow. When a crush commences, it is al- 

 most impossible to prevent it overrunning all the work, 

 except it is resisted by a barrier of coal, or by stronger 

 pillars in another district of the work. In wastes of 

 very great extent, the progress of a crush is some- 

 times stopped by cutting out a line of pillars betwixt 

 the crush and the wall-faces, so that when the crush 

 comes to the void, the superincumbent strata break 

 down from the waste to the surface. When a crush 

 overruns the whole work, the superincumbent strata 

 break over at the wall-faces. When this happens, 

 the works have to be opened up anew, by cutting 

 roads and making air-courses through the crushed 

 waste. When creeps and crushes are extensive, they 

 derange the whole economy of the work, by destroy- 

 ing all the roads and air-courses ; and the re-establisli- 

 ment of the works is attended with uncommon haz- 

 ard, labour, and expense. The improved plan of 

 working the mines in pannel-work, as brought into 

 practice by Mr. Buddie, is highly beneficial in pre- 

 venting creeps or crushes, and if they do take place in 

 one pannel of work, the pannel-walls act as com- 

 plete barriers against their extending to the other pan- 

 nels. 



When the pillars of a colliery are to be wrought by 

 taking a part of every pillar, it sometimes happens 

 that the remaining portions of the pillars resist the 

 weight of the superincumbent strata for a considerable 

 time. In this case there have been instances 'of the 

 weak pillars giving way in a moment, without warn- 

 ing, and forcing the air of the waste up the shafts with 

 inconceivable force ; a case attended with imminent 

 danger to the workmen. 



Coal-mines take fire either from explosions of in- 

 flammable air or spontaneous ignition, occasioned by 

 the decomposition of pyrites amongst the rubbish of 

 the mine. The method adopted for extinguishing 

 such fire, when occasioned by inflammable air, has 

 been already mentioned when treating of ventilation. 

 In coals liable to spontaneous ignition, the effectual 

 plan of prevention is, to allow none of the small coal 

 and rubbish to remain in the wastes ; but if this can- 

 not be done, the old wastes should be insulated from 

 the new works, by buildings betwixt the surrounding 

 pillars, to prevent the access of air to the rubbish. 

 When wastes containing this kind of rubbish take fire 

 to any considerable extent, the application of water 

 has very little effect ; for though it may in some de- 

 gree extinguish the fire at that particular spot, it great- 

 ly promotes ignition amongst the adjoining rubbish, 

 by bringing on a more rapid decomposition of the py- 

 rites. The remedy in common practice is to build off 

 the burning waste with air-tight walls, and prevent 

 all access of air. Though these remedies generally 

 prevent the fire from spreading farther, a very slow 

 combustion frequently goes on for many years in the 

 ignited wastes, There have been instances of this kind 

 of fire continuing for near a century. When coals 

 which are free of pyrites take fire by accident, if they 

 cannot be extinguished by any of the methods before 

 mentioned, the last resort is to allow the wastes to fill 

 with water until the fire is extinguished. This me- 

 thod cannot be applied in coals liable to spontaneous 

 ignition, for as soon as the water is drawn from the 

 wastes, this ignition would take place through the 

 whole extent of the works. 



In prosecuting the workings of a colliery, the ordi- Mines ol 

 nary growth of water which is pumped up by the en- Co '- 

 ginc is sometimes suddenly increased from fissures in "~"~ """" 

 the strata communicating with great bodies of water. Jf n"" 1 "" 

 Such additional feeder.-, are measured as to quantity m -, n j n " b, 

 everyday, in order to find if they abate or not. If water." 

 they do not abate, and the engine is unable to draw 

 this additional quantity, more machinery must be put 

 on to keep the mine dry ; but if this cannot be effect- 

 ed, and the growth of water b" so great as to threaten 

 the ruin of the colliery, this extra growth is frequent- 

 ly kept back by placing strong dams of wood in the Dams, 

 mines leaJing to the district from whence the water 

 issues. This may be done where there is a strong 

 barrier wall, and a few narrow mines through it ; but 

 it is altogether impracticable along an extended line of 

 pillars. These dams are made of very dry fir logs, 

 about six feet in length, each log being dressed smooth 

 and square with a plane. A seat is cut in the mine, 

 where the dam will lie most secure, the inner head 

 next the water being wider than the other end. In 

 order the more effectually to resist the pressure, each 

 log is dressed to this bevel, and the sole of the dam is 

 laid with a bed of oakum before the logs are laid down, 

 a strong cast iron pipe of size sufficient to let a man 

 pass through, is placed in the dam, which pipe is of a 

 conical shape, the wide end being towards the inside, 

 the whole space is then filled up with logs. The outer 

 and inner heads of the dam are then wedged in a regu- 

 lar manner, in lines parallel to the joints of the logs, 

 with very thin dry fir wedges, and that until no more 

 wedges can be driven. The men for wedging the in- 

 ner head, pass and repass through the iron pipe ; and 

 the last of these, when the wedging is completed, draws 

 after him a wooden plug, which shuts up the iron pipe, 

 and prevents the water from passing through. This 

 plug is longer than the dam, so that a piece of it pro- 

 jects beyond the lower end, by which it is drawn tight 

 into the pipe, and then made perfectly tight b}' wedg- 

 ing. If more dams than one have to be put in, the 

 iron pipe is only necessary for the dam which is to be 

 last wedged. Dams of this kind will resist almost any 

 pressure of water; but if the roof or pavement is bad, 

 particularly the latter, there have been instances of the 

 water, from its excessive pressure, passing through the 

 strata under the dam, and blowing up the pavement at 

 the lower end of it, by which the colliery has been in- 

 stantly ruined, and the lives of the men put in immi- 

 nent hazard ; the same accident is liable to happen by 

 the water passing under the barrier walls, or bursting 

 it where thin. It is not found expedient, where there is 

 great pressure, to form these dams in the boards or 

 rooms, the width being too great : mines of about six feet 

 wide are preferred. Water has by this plan been kept 

 back under a pressure of 130 fathoms. Plate CCCXCIV. PLATE 

 Fig. 9. represents the plan of a dam in a narrowwnine, ftcxciv. 

 for resisting a great pressure. Fig. 10. represents a P'g-9l 

 plan of a dam placed in a room or board, where the 

 pressure is much less. 



In cases where the communication from an extra 

 feeder of water to the engine pit-bottom is through a 

 staple or blind pit, such water is prevented from de- 

 scending to the workings, either by a very strong wa. 

 ter- tight scaffolding, made of timber, supported by dia- 

 gonal stays from the sides of the pit below, or a stone 

 arch may be thrown in the pit, and covered with a 

 thick moating of clay ; these are generally placed at a 

 bed of the strata which is impervious to water. 



