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, ana 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, Portugal, the West Indies, and America. The principal seat of the coal trade is in the northern 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 dip, 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 adit 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 waters 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-ings, 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 coalmine may be gathered from the accompanying section of Bradley Coal Mine, near Bilston, 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 head-winning way; F, the bolt hole, made to cause a free circulation of air through the mine; (should any part take fire, the bolt hole is built up;) G, 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; l, 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; O, 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; U, 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.