CHAPTER X. WORKING MACHINERY. Drawing and air shafts-Importance of VentilationDraining the Mine-Bearing of strata-Early contrivances for raising the water-Bucket wheelsSteam-engine-Boulton and Watt-Pumping apparatus-Subterranean Steam-engines-Deep Pits divided by Bratticing-Head Gear-WhimseySteam-engine and counterpoise-Hydraulic Machinery for raising Coals-Corves, Trams, Buckets, and Waggons-Screen-Entrance to Pits by Canals and Footrails. ASSUMING, in accordance with the preceding Chapter, that a shaft is sunk to the coal, and properly secured against the irruption of loose shattery sand or gravel, as well as of water, by wood or iron tubbing, it is proper farther to state, that this shaft must either be divided down the middle by a partition of boards, so as to form upcast and downcast tubes for ventilation, and, in some cases, to serve for engine-pumps, as well as drawing coals; or else, that another pit must be sunk, to be connected with the former by means of an underground drift, and thus afford a circulation of air, In very deep pits, the saving of expense commonly compels the former course; in other cases, the latter method is adopted. In Staffordshire, it is usual to sink "a pair of pits"; the establishment of works for a single colliery being called "a plant," or plantation. That most important particular in the economy of our mines, and upon which the health and lives of the colliers so much depend-namely, Ventilationhas been the theme of a great deal of discussion— not always temperately conducted. The philanthropist has sometimes upbraided the coal-viewer with murder, for neglecting the trial of some theory of injecting or circulating air; while the viewer, in turn, has occasionally scouted, with perhaps too little ceremony, schemes which appeared ingenious and plausible enough on paper, but which might be to him obviously unavailable in practice. It will at once be apparent, that the mere existence of two or more pits at any given distance from each other, would do little, if any thing, toward cooling the interior of the mine, and changing the respirable air the pits would simply stand, full of air, as in two vessels, under similar circumstances, water would stand at one level. Air must, therefore, be either artificially forced down one of the vents, or it must be made to descend by altering the quality of the subincumbent portion: both these methods have been resorted tothe latter with most success. As the natural tendency of the atmosphere to restore its equilibrium, causes the general volume to travel by the nearest direct channel toward any place where a partial vacuum is formed; and as the object of the miner is to counteract, or rather to take advantage of, this law, stoppages are so arranged in the workings, by DRAINING THE MINE. 193 trap-doors or other means, that the current brought down the working pit, instead of being allowed to rush to the air-pit directly, is first made to circulate as deviously and extensively as possible. We shall have occasion to advert to this arrangement again, and more particularly. The draught is created, or a sort of vacuum formed in the air-pit, sometimes simply by the suspension of a pan of burning coals, but more perfectly by closing the pit overhead, with the exception of a chimney, and keeping up a fire therein, either near the top or at the bottom, as most convenient: thus by rarifying the air at this extremity, that portion of it which has been rendered foul by breathing rushes to the heat, while, to supply its place, a new and unvitiated volume is forced down the open pit. The next object of attention, and one equally important with ventilation, is the Draining of the Works. In almost every colliery there is more or less water— in most so much, that the pumping of it out of the workings is an affair of considerable importance; and sometimes it is necessary to erect the steam-engine, and work it for this purpose, during the sinking-the pumps being suspended and lengthened as the shaft increases in depth. It must at once occur to the reader, that, as the strata of every coal field have a certain inclination with respect to the horizon, called the dip and rise, as well as commonly a level line of bearing, forming right angles therewith (to say nothing of * The boys who attend to open and shut these doors, are called trappers: they have seats near the doors, and remain by them all the time the pit is at work. As these trap-doors are, as it were, the air-valves, by means of which the ventilation of the works, in connection with underground passages, is kept up, a proper attention to them is a matter of great importance. They are, however, on account of the simplicity of the duty to be performed, commonly entrusted to young boys on their first entrance upon work. the many other complex modifications occurring in practice); and, as the drainage will generally follow the descent of the measures, it will be necessary to select such a situation for the engine-pit, that, as the excavations in getting the coal are extended, the water, instead of accumulating in the works, may run off to the place of the pumps. With this design it is usual to sink the engine-pit at the lower part of the field, the drawing shaft being at a short distance above on the rise of the strata. The annexed diagram will sufficiently explain the arrangement. Suppose the cross lines to indicate a tract containing coal measures, which rise to the west and dip towards the east, the cross bearing of the strata having a slight inclination from north to south. The course of winning would be-having sunk the engine-pit at A, nearest the lowest angle of the ground, and the working-pit at B, a little higher up, and having opened a passage between them, the next operation would be, to cut a drift or water-course along the lowermost level of the tract from A to D, so that when what is called the winning headway, or main thoroughfare, is excavated from A to c, and the engine and drawing apparatus got to work, the coal is said to be won. The water from the workings which are carried on the rise, mostly flowing off by means of cross galleries to the sump, or well in which the pumps work; some portion also, it may be, running down the headway A c. Prior to Mr. Newcomen's application of steam BUCKET WHEELS. 195 to raising water from coal mines, both the water and coal were usually raised by means of engines wrought by horses, a method still in use among some land-sale collieries. About two centuries ago, a patent was granted by James VI. of Scotland, for the discovery of an engine for raising water from coal mines.* In 1630, a charter was also given to a person called David Ramsay for a similar invention.† Sometime after "Master Beaumont, a gentleman from the south, brought with him rare engines to draw water out of the pits," at Newcastle. At the Lumley collieries, about 1676, "the engines were placed in the lowest places, that there may be the less way for the water to rise; and if there be a running stream to work the engines it is happy. Chain pumps are the best engines, for they draw constant and even: but they can have but two stories of them; the second being with an axletree of seven or eight fathoms, and the deepest story is wrought by buckets, and a wheel and ropes with the force at the top."§ These contrivances were, on the whole, clumsy, dangerous, expensive, and inefficient. Mr. Bald, in his view of the coal trade of Scotland, printed in 1812, informs us that about 1690, water wheels and chains of buckets were commonly employed to drain collieries in that country. The axle of the wheel extended across the pit mouth, and small wheels were fixed upon the axle to receive endless chains of two or three tiers-which reached down to the coal. To these chains were attached a number of oblong wooden buckets or troughs in a horizontal position, which circulated continually with the chains ascending on one side and descending on Arn. Hist. of Edinb. 66. Rymer Fœd. 1. xix. f. 189. |