COAL MINE. Strata of coal are to be met with in various parts of the globe, as France, Germany, Sweden, America, Australia, and we believe likewise in India ; but in no country in such profusion, or of so good a quality, as in Great Britain; and to this circumstance we may mainly attribute our commercial greatness, and our superiority in almost every branch of manufacture. In coal mining, and the carrying trade, a vast portion of our population is employed, besides many hundreds of thousands of tons of shipping constantly engaged in transporting this valuable mineral not only to all parts of our own coasts, and up our rivers, but to almost every part of the Netherlands, France, Spain, Po the West Indies, and America. The principal seat of the coal trade is and eastern parts of England, and the most important coal works are those of Newcastle and Whitehaven; at the latter place some of the mines extend more than a mile under the sea, and at a depth considerably greater below its surface than has been reached in any part of the world, the deep mines of South America being situated upon lofty mountains considerably elevated above the surface of the earth.
We shall now proceed to give a brief description of the method of working a coal mine. To ascertain whether coal is concealed beneath the surface at any place, recourse is had to boring, by a process and implements similar to what we have already described in our account of the method of boring for water ; and an account is carefully kept of the different strata cut through, and of the depths to which they extend before arriving at the principal bed of coal; and the thickness of the coal strata in different situations, as well as the dip or inclination of the strata, (for they seldom lie horizontal,) are ascertained by the same means. The working is usually commenced upon the as it is termed, or where the depression of the strata of coal is greatest. The first consideration is the means of draining off the water from the feeders and springs with which the coal is usually intersected. If the situation and other circumstances will admit of it, an edit is driven through the side of the hill to the lowest part of the mine, and the water runs off by it to a lower level ; but if this cannot be effected, the water is raised by pumps worked by horses, water, or steam, according to circumstances. For this purpose a pit or shaft, termed the "engine shaft," is sunk (generally upon the dip of the coal), in order to allow the water to drain from the workings and to keep them dry. In this shaft the pumps are placed, divided into sets at the various depths of the mine, the lowest set delivering its water into a cistern, from which it is raised by the next set of pumps above it, and so on to the surface, the lift for each set seldom exceeding 25 to 30 fathoms. When the required depth is attained, a portion of coal is worked dipward of the engine-shaft, forming a cistern for the *aters to collect in. A level is then cut, from the bottom of the engine-shaft, called the gateway, or winning headway, which, as the works proceed, is carried the whole length of the mine, and is from 8 to 10 feet high, and 9 feet wide. When the gateway has proceeded to the required distance from the engine shaft, another shaft is sunk to meet it, called the coal shaft, or pit, by which the coals are conveyed to the surface in baskets by a gin. From the gateway, or winning headway, the coal is worked from passages cut at right angles, called "rooms," which are about 12 feet wide ; and other passages again are cut at right angles to the rooms, which open from one room into the next, and are called " thoroughs," or thirt lags, the coal remaining thus forming pillars for the support of the roof. When the coal is of a firm texture, from two-thirds to three-fourths may be got out at the first working; but in other cases little more than a half. Two large blocks or pillars, 15 or 20 yards long by 10 or 15 yards wide, are left to protect engine and coal-pit, in case of the falling in of the mine. The coals are brought to the„pit or shaft in small cars, drawn by horses when the workings are wide and moderately level; but if too steep or narrow, are drawn by men in baskets upon trucks ; or if too steep for this, are carried in baskets upon the backs of women. A general idea of the operations and arrangements of a coal mine may be gathered from the accompanying section of Bradley Coal Mine, near Banton, in Staffordshire. A, the whimsey, or steam-engine for raising the coal from the bottom of the shaft ; B, the banksman who lands the same ; C, one of the shafts of the mine ; D, a passage from one shaft to another ; E, the gateway, or bead-winning way ; F, the bolt hole, made to cause a free circula tion of air through the mine; (should any part take fire, the bolt hole is built up;) Cl, pillars left in working the ten-yard coal, to support the superjacent strata; H, an excavation called a still, or room, by the colliers, who, after the gateway is cut, begin thus to work the coal, or hole-under ; I, the ribs through which the air-way is cut ; J, lights ; K, a man who hangs on the skips, and rakes the gateway ; L M N, miners heading, holing, and shovelling out the slack or small coal ; 0, slack carrier ; P, miner working on a scaffold; Q, the spern, a small piece of coal left as a support to many tons above, which fall when this is taken away; R, a collier on a scaffold, taking out the spern as far as he can reach with a pick ; S, a collier standing upon a heap of slack, called the gob, with a prong used for that work, which cannot be safely done with a pick ; T, a collier breaking or turning out coal ; II, a collier loading a skip ; V, a collier breaking the large coal with a wedge ; W, a driver with an empty skip, X, a driver with a loaded skip; Y, a skip being drawn up the shaft by the engine ; Z, a pillar, called the man of war, left to support the upper strata until the lower are worked ; it is then taken away, and the upper coal falls down. The different strata that are cut through to arrive at the principal bed of the coal are exhibited on the left of the shaft, by variously shaded portions of the solid earth, extending in the Bradley mine to the depth of about 111 feet,—the depth to the bottom of the shaft is 139 feet 4 inches. In the extensive collieries in the vicinity of Newcastle a complicated and expensive system of ventilation has been adopted, in order to guard against the disastrous consequences which result from an accumulation of fire-damp or hydrogen gas ; but from the calamitous explosions, which are of such frequent occurrence, it is but too clear that the system is deplorably inefficient, and calls loudly for improvement. The accompanying sketch represents, on a small
scale, the plan which is pursued to counteract the effects of that fatal evil, and to spread throughout the workings a sufficient quantity of fresh air. The dark parts in the plan represent the pillars of coal left to support the roof, and the light parts the workings. There are generally two descents or more to the mine, as we have already stated, which are distinguished by the terms of the downcast and upca,t shaft. A is the downcast shaft by which the air descends; the current of the air is represented by the waved line, which is carried through the main passages only, the subways which diverge from them being stopped by the brattices ; and its motion is accelerated by the heat of a large fur nace, situated at the bottom of the upcast shaft B; and thus the air, after traversing the whole of the workings, ascends the shaft B. An exhausting pump placed near the upper end of the upcast shaft B is sometimes substituted for the dangerous expedient of the furnace at the bottom of the shaft. But when particular parts of the mine are subject to rapid accumulations of fire damp, recourse is had to the firing process, which is usually performed by means of an apparatus, consisting of a long pole, or a series of poles, fitting one into another like a fishing-rod, so as to be elevated to the break, or pot-hole, where the fire-damp has accumulated ; at the upper end of this pole is a small sheeve or wheel, over which a copper wire passes, of sufficient length to reach to the horse stable from any part of the mine ; this done, the pole is firmly fixed in the place where the gas lodges. A candle, fixed to a piece of lead or other substance to keep it upright when suspended, is carried by the fireman as far towards the explosive region as safety will admit, when it is set upon the floor, and fastened to one end of the copper wire, after which the firemen retire to the stable, which is made strong and well secured, in order to barricade them: the other end of the wire is brought through a crevice in the door, and by this means the light is drawn up to its destination ; and the gas which has accumulated, coming in contact with the flame, ignites and explodes. In some instances the firemen remain pent up a considerable time in the greatest suspense, owing to some accidental circumstance having put the candle out before it reaches the pot-hok, when they are fearful of venturing, from the uncertainty of what may be the event. In many instances it has been found necessary to explode these lodgments three times a day, at each time clearing the mines of all the work men except the firemen ; the necessity of which has been occasioned by the miners cutting down strata or measures of coal, so as to render the roof higher than the general run, of six or eight feet seams, and by these means making the extra elevation too great to be effected by the diluting current. In fact, where the roof of a coal mine (where the seam is thirty-six feet thick,) is cut down, no means but the firing process could suspend for a single day the destructive effects produced by an explosion of the whole mine. To obviate the dangers and difficulties of the firing process, Mr. James Ryan, of Netherton colliery, near Durham, who had been for many years engaged in working mines, invented, in lien of it, a simple, effectual, and economical system of ventilation, by which the fire-damp, or inflammable gas, was carried off upwards from the mine; whilst by another arrangement he caused the carbonic acid gas (or choke-damp) to pass off into the water level. In attempting to get his plans of ventilation tried at various mines, he met with the most stubborn opposition; and although in every instance in which he was allowed to introduce his system, he was eminently successful, yet, from the misrepresentations of ignorance and jealousy, his system of ventilation has been adopted in very few mines, and the firing pro cess is still very generally resorted to Mr. Wood, of Summer Hill Grove, Nor thumberland, has however invented an apparatus by which the firing may be effected without any personal danger. The annexed diagram represents the interior of a coal mine in perspective, with Mr. Wood's apparatus employed in igniting the gas. It consists of a common Dutch striking clock, in which the descent of a weight at a previously determined hour raises a lever having a counterbalance weight : this lever acting upon another lever, causes a match, charged with oxymuriate of potash, to be dipped into a bottle containing sulphuric acid ; the counterbalance weight on the first lever immediately afterwards draws the match out of the bottle, when the contact of the air causes the match to ignite, and to set fire to a train of combustible matter connected with it, consisting of cotton or tow saturated with spirits of turpentine. a represents the weight of the clock, which is set to go off at the time denoted ; a projecting piece at the bottom of the weight presses in its descent upon one extremity of a lever, which turns upon a fulcrum at b : the other end of this lever is provided with a roller c, which raises the loaded end cl of another lever, supported upon a standard at e; at f is a rod attached by a joint to the other extremity of the second lever, and at the lower end it is jointed to a small block, to which is fixed the match. To the match are attached some loosely twisted filaments of cotton, which are carried upward, and wound round an iron rod as loosely as possible, so as to form a large bunch of easily ignitable matter, to further which the whole is saturated with spirits of turpentine : the iron rod containing the bunch of cotton slides up and down in a fixed standard i, as represented ; and from this point a train is made to other parts of the mine, where the inflammable gas may have collected in a detached volume, by means of strips of brown paper dipped in oil of turpentine, which are strung together and suspended in festoons on standards fixed in the ground. The clock being set to go off when all the workmen are absent from the mine or at rest, the weight operates upon the lever at the precise period determined upon, ignites the match and the train, and thus destroys all the inflammable gas.