mode of working. CHAP. 2. the bottom or under side of a seam of coal, or by means of shafts sunk to History and the same point, the foul air is expelled. The next operation in opening a mine is to drive the water-levels in the coal, or to cut a gate or passage each way so as to let the water have a gentle fall towards the pumping shaft. These operations are common to all collieries; but then the nature of the strata which immediately cover the coal is to be considered, and it must be determined what lengths of the banks or works can be opened at one time, and what direction such banks or faces of the works must have. In Derbyshire and its environs, coal seams having tolerably good roofs, with their water-levels ranging nearly parallel with the slines or the lengthway joints of the coal, the pits are for the most part worked the long way or with long banks, which is the most economical method when it is practical, both in the expenses of working and in the produce of coal. Crossgates or jenny-gates are then driven, which are passages not only giving admission to the pure air, but serving for different roads to the works; and the regular operations commences by a set of colliers, called holers, who begin in the night and hole or undermine all the bank or face of the coal, by a channel or nick from twenty to thirty inches back, and four to six inches high in front; pecking out the holeing stuff with a light and sharp tool called a pick, hack, or maundrel: and placing strutts of wood in such places where the coal seems likely to fall, in consequence of being so undermined. When the holers have finished their operations, a new set of men, called hammer-men or drivers, enter the works. These fall, or force down, large masses of coal, by means of long and sharp iron wedges, which, being broken into smaller pieces, are placed in corves or trams and drawn to the top of the pit, by the whimsey, or horse-gin used for that purpose. The corve is a square shallow wooden box, having an iron handle over it in smaller works, and being slung with chains in larger works: in some places the corve contains about nine pecks, in others two hundred weight. After the day's work is completed, the portion of roof deprived of its natural support is propped up by stout posts of wood, sometimes placed at little more than a yard apart, and at other times only here and there for precaution, where joints appear in the rock above. After this, on the following day, the same operations are repeated. Where the roofs prove good the props are moved forward; and in some works cast iron supports (the invention of Mr. John Charlton) are made use of with great advantage. The coals of Derbyshire are for the most part worked by lessees, but not above eight or nine great landowners work the pits on their own account except for their own and their neighbours' consumption. Collieries are generally let, by the acre of coals that are worked, ascertained annually by survey and measurement of the subterranean works. Mr. Farey states the rents to be from £50. to £180. per acre, according to various circumstances. Other coal owners reserve a fixed rent, which varies from 4d. to 16d. upon every ton sold at the pit. There are many varieties of coal. The hard is much esteemed, particularly when it is of a bright black colour. The soft coal of Derbyshire do not cake or crozle together except in some instances, and then they are called smithy coal. This last mentioned coal is slattery and often sulphureous. It is much used for burning limestone and the manufacture of iron goods. A large quantity of it is converted into coke. Of the former, which is by far the most valuable, the diversities will be found to be stated in the list of collieries. MEASURES OF STRATA penetrated in various coAL PITS. Shipley deep field. The terms in the following list are generally Provincial, and used by the CHAP. 2. History and mode of working. Light coloured bind with ironstone... 5 1 1 1 1 0 Dark bind with some small ironstone 2 10 Light coloured clunch.................... Grey stoney bind with ironstone 226 .... 70 3 01 4 1 1 4 2 18 Soft coal.......................................................................... Hard grey stone................................................ 1 10 Light coloured bind with ironstone... 1 0 4 13 1 2 C11 0 2 0 Dark clunch......................................................... 309 V Dark bind with much ironstone ...... 25 1 6 014 20 0. 0 1 4 026 Dark clunch.... 020 026 316 Brown rock stone, or the Shipley quar ry stone.... -Grey stoney bind with ironstone beds 10 1 Minge coal, formerly called the old : Dark clunch....................................... Dark stoney bind with ironstone ...... 316 0 1 2 Blue bind fuli of small ironstone 7 2 10 Soft coal called the foot coal.......... 009 Grey stoney clunch........................ 9 1 3 8 Scud or ming coal. 10 3 Main hard coal Strong dark bind with ironstone 4 13 Soft coal Blue bind full of good ironstone...... 0 16 Soft coal...** Light coloured soft clunch..... 0 1 4 128 West-Hallam. yds.ft.in. ...11 0 0 Ironstone, in angular nodules (Serin) 0 0 13 Clay...... 6 yds. ft. in. phur of lead in small fissures (Scrin black) 003 0 1 Clay 020 Clay........ Ironstone, in cheese-shaped nodules, containing septariæ of carbonate of iron (Cheeses)........... Conie clay, composed of multifarious concentric ramified cones; containing on analysis, iron 11 0. Carbonate of lime 78, 5. Silex 2, 5. Manganese 8 0. in 100 parts (Bears) 0 0 3 Ironstone, abounding with petrified muscle shells, contains 25 per cent. of iron (Muscle band).................................................. Ironstone, in cheese-shaped nodules, containing septariæ of carbonate of fron (Old man)........................... 004 Clay......... Ironstone, in cheese-shaped nodules, containing septariæ of carbonate of iron (Old woman) ...................................................................... 004 003 Clay....... 016 Ironstone in beds (Dunstone). 006 ..... 003 taining pisolites (Balls) 016 Clay. 016 Ironstone, in ovate nodules, contain CHAP. 2. Measures of Strata. CHAP. 2. Damps. Nature of Coal works are subject to two very considerable evils: these are, what the workmen term, fire damp and choak damp.* The former is a gas chiefly composed of hydrogen, which often issues in streams from the cracks and joints in coal and shale strata, and by its lightness occupies the tops of gates or hollows. In such situations it becomes mixed with the atmospheric air and is liable to explode, not only with serious injury to the miners, but, when the quantity is considerable, it occasions extensive devastation with loss of lives. The latter settles at the bottom of shafts, where there is no circulation of air, and often proves fatal to animal life, by suffocation. When the hydrogen gas is accidentally set on fire, the men throw themselves on their faces, on the ground, to avoid the return of the blast, as there is more danger to be apprehended from the vacuum formed by the total consumption of the inflammable gas, than from the effect which the fire has upon them. It seldom happens after the explosion that the men are much burnt; they suffer more after an explosion of the fire damp from the after damp, or carbonic acid gas, which is the produce of this explosion, and fills up the vacuum occasioned by it. After an accident of this kind, it is considered dangerous to enter the pit for some days, on which account it is to be feared, many lives are lost, which might have been saved by immediate assistance. With respect to the nature of the coal of Derbyshire, we extract the following results from Mr. Mushet's experiments: Ashes. 45.50 52.456 2.044 42.83 52.882 4.288 47.00 48.362 4.638 Specific gr. Gritstone and Shale. First Grit Gritstone and shale. These strata, although they possess many of the characteristics of coal measures, with numerous vegetable impressions, which are not met with in the lower strata, nor in any stratum covering the red marl. The gritstone and shale contain, however, no seams of coal of the least value. The First grit rock, or Millstone grit rock, composes a very considerable part of the silicious rock scenery of this county. In several places it has been proved to be 120 yards thick, composed chiefly of a very coarsegrained white freestone, sometimes inclined to a yellow and sometimes to a red colour. As it is easily worked, notwithstanding the extreme hardness of its particles, it may be regarded as equal, if not superior to any of the freestones in England. The Peak-millstones, which are celebrated all over the kingdom, are made from this stratum. These millstones are made at many places to the north of Belper, but chiefly at Old Booth Edge, "Coal mines, it is well known, are subject to fatal explosions of what is called the fire damp, or earburetted hydrogen gas. This gas appears to be generated by the decomposition of iron pyrites in coal, and may be often heard issuing from the fissures in a coal bed with a bubbling noise, as it forces the water out along with it. The choke damp, as it is called, is either carbonic acid gas (fixed air) or the unrespirable residue of air left after explosions when all the oxygen is consumed." (Bakewell's Introd.) Mr. Bakewell is of opinion that the number of lives destroyed by explosions in coal mines has increased since the introduction of the safety-lamp-"from causes which do not invalidate the value of the discovery, if its use were confined within the limits which its illustrious inventor must have proposed." (Ibid. Appendix.) |