In some years after the Restoration, there were about 200,000 chaldrons burnt in London; in 1670 about 270,000 chaldrons; and at the Revolution, upwards of 300,000 chaldrons; and at present, above 1,000,000 are annually consumed here. In Scotland there are coals sufficient to supply the consumption, and also to export; but a considerable quantity of English coals are imported, because they are found of a stronger heat, and otherwise better adapted to several manufactures. In Ireland, though they have coal, yet they take annually to the value of £40,000 from England, and £20,000 from Scotland. Maliciously setting fire to coal mines is felony, by stat. 20 Geo. II. c. 32. sect. 6. COAL-MINES, FOREIGN. There are several other countries in Europe, which possess considerable coal-mines; as France, Liege, Germany, and Sweden: also on the other side of the Atlantic Ocean; in Newfoundland, Cape-Breton, Canada, and some of the states of New England. But in all these countries the coal is of a quality much inferior to the British, and entirely unfit to be used in many manufactures; so that they are obliged to import great quantities from Britain for the use of their manufactures of iron, &c. The INLAND COAL TRADE, that is, carrying coals from Newcastle, Sunderland, Blith, and other adjacent places in the north of England, as also from the Frith of Forth to London, and the port-towns on the coast all the way, as well as on this side of Newcastle, south, as up the channel as high as Portsmouth west, is an important branch of commerce, and employs abundance of shipping and seamen; in so much that, in a time of urgent necessity, the coalery navigation alone has been able to supply the government with a body of seamen for the royal navy, able to man a considerable fleet at a very short warning, and that without difficulty. The Whitehaven coaleries in Cumberland, belonging to lord Lonsdale, which furnish several counties in Ireland with coals, constantly employ upwards of 2000 seamen; and are a noble nursery for the navy of this kingdom. And not only do the pit coals sufficiently supply all the ports, but, by those ports and the navigable rivers, all the adjacent counties very far inland. In short, coals, though not an exclusive, yet may, with propriety, be styled a peculiar blessing to Britain from their great plenty, their acknowledged excellence, and their being found in such places as are conveniently situated for exportation. Nor is there any danger of the export trade being lessened even by the several duties that have been laid upon them; for the foreign consumption being founded in necessity, with regard to manufactures, and in economy, where they are used for convenience (wood and turf being dearer than coals with the duty), we need be in no fear of the markets declining. There is as little room to be alarmed from an apprehension of their being exhausted, as the present works are capable of supplying us for a long series of years, and there are many other mines ready to be opened when these shall fail. Besides, there are known to be coals in many parts of the three kingdoms, which hitherto there has been no encouragement to work. Besides the value of this com modity as a conveniency of life, as an article of commerce, and as giving rise to a nursery of seamen for the increase of the marine, other important advantages deserve to be noticed. Coals are, in many respects, and in a very high degree, useful to the landed interest; not only by raising exceedingly the real value, and of course the purchase, of those lands in which they are found, and those through which it is neces sary to pass from the works to the places where they are embarked (which are styled way-leaves, and are set at as high rents as any lands in Britain); but from the general improvements they have occasioned. Very few counties are now better cultivated than Northumberland, and the same effects have been produced, in a greater or less degree, in other places. Thousands of laborious people are employed in and about the mines; thousands more in conveying them to the ports, and on board the ships; to say nothing of those that draw their subsistence from the carriage of them by land to supply families, &c. Great numbers also live in a superior station; as stewards, directors, factors, agents, book-keepers, &c. To these we may add the extraordinary encouragement given to ingenious artists who have invented, and the numerous workmen continually employed about those several curious and costly machines, which, for a variety of purposes in this business, are in continual use, and of course in continual wear: we may join to these the multitudes that obtain their living from the manufactures in which they are employed, and which could not be carried on but by the help and cheapness of coals. Lastly, the produce of coals exported, which amounts to a very considerable sum, besides being profitable to the owners, merchants, and mariners, is so much clear gain to the nation. It might be expected, that a trade so beneficial to individuals, and to the nation in general, and which has been gra dually increasing for several centuries past, would have been advanced by this time to very great perfection, and reduced to a regular system. But, in one very essential respect, it is found to be quite otherwise. The art of working coalmines in the most profitable manner is indeed highly improved, but the principles of the art, that of searching for and discovering coal in any district of country, where it has not yet been found, has never, that we know of, been treated in so systematic a manner, as in the Encyclopædia Britannica. We shall lay, therefore, before our readers, the following citation from that useful work: The terrestrial matters which compose the solid parts of the earth (in coal mines) are disposed in strata, beds, or layers, the under surface of one bearing against or lying upon the upper surface of that below it, which last bears or lies on the next below in the same manner. These strata consist of very different kinds of matters, such as free-stone, lime-stone, metalstone, whin-stone, coal, &c. as will be particularly specified in the sequel. Some of these strata are of a considerable thickness, being often found from 100 to 200 feet or upwards, nearly of the same kind of matter from the superior to the inferior surface; and others are found of the least thickness imaginable, one inch or less. All these strata are divided or parted from each other laterally, either by their even, smooth, polished surfaces, with very thin lamina of soft or dusty mat ter betwixt them, called the parting, which renders them easy to separate; or else only by the surfaces closely conjoined to each other, without any visible matter interposed betwixt them; yet the different substance of each stratum is not the least intermixed, though sometimes they adhere so strongly together, that it is very difficult to part or disjoin them in this last case they are said to have a bad parting. Besides this principal division or parting laterally, there are, in some strata, secondary divisions or parting also laterally, separating or approaching towards a separation of the same stratum, into parts of different thicknesses, nearly parallel to each other; in the same manner as the principal partings divide the different strata from each other; but these secondary ones are not so strong or visible, nor make so effectual a parting, as the principal ones do; and are only met with in such strata as are not of an uniform hardness, texture, or color, from the upper to the under surface. There are other divisions or partings called backs, in almost every stratum, which cross the former lateral ones longitudinally, and cut the whole stratum through its two surfaces into long rhomboidal figures. These again are crossed by others called cutters, running either in an oblique or perpendicular direction to the last mentioned backs, and also cut the stratum through its two surfaces. Both these backs and cutters generally extend from the upper or superior stratum down through several of the lower ones, so that these backs and cutters, together with the lateral partings beforementioned divide every stratum into innumerable cubic, prismatic, and rhomboidal figures, according to the thickness of the stratum, and the position and number of the backs and cutters. They sometimes have a kind of thin partition of dusty or soft matter in them, and sometimes none, like the first mentioned partings; but the softer kind of strata generally have more backs and cutters than the harder kind, and do not extend through the others.' Let A, B, C, D, E, F, G, plate COAL-MINES, fig. 1, represent the principal partings, or the upper and under surfaces of any stratum; then a, b, c, d, e, f, will represent the secondary lateral partings nearly parallel to the principal ones: g, h, i, k, l, m, the longitudinal partings called backs; n, o, p, q, r, s, the cross partings called cutters, crossing the last mentioned ones either obliquely or perpendicular. In all places where the strata lie regular, they are divided and subdivided in the manner above mentioned; and sometimes in this manner extend through a pretty large district of country: though it is often other wise; for their regularity is frequently interrupted, and the strata broken and disordered, by sundry chasms, breaches or fissures, which are differently denominated according to their various dimensions, and the matters with which they are filled, viz. dikes, hitches, and troubles. I. Dikes are the largest kinds of fissures. They seem to be nothing but a crack or breach of the solid strata, occasioned by one part of them being broken away and fallen from the other. They generally run in a straight line for a considerable length, and penetrate from the surface to the greatest depth ever yet tried, in a direction sometimes perpendicular to the horizon, and sometimes obliquely the same kind of strata are found lying upon each other in the same order, but the whole of them as greatly elevated or depressed on the one side of the dike as on the other. These fissures are sometimes two or three feet wide, and sometimes many fathoms. If the fissure or dike be of any considerable width, it is generally filled with heterogeneous matter, different from that of the solid earth on each side of it. It is sometimes found filled with clay, gravel, or sand; sometimes with a confused mass of different kinds of stone lying edgeways; and at other times with a solid body of free-stone, or even whin-stone. When the fissure is of no great width, as suppose two or three feet only, it is then usually found filled with a confused mixture of the different matters which compose the adjoing strata, consolidated into one mass. If the dike run or stretch north and south, and the same kind of strata are found on the east side of the dike, in a situation with respect to the horizon ten or twenty fathoms lower than on the other side, it is then said to be a dip-dike, or downcast dike of ten or twenty fathoms to the eastward; -or counting from the east, it is then said to be a rise dike or up-cast of so many fathoms westward. If the strata on one side are not much higher or lower with respect to the horizontal line, than those on the other, but only broken off and removed to a certain distance, it is then said to be a dike of so many fathoms thick; and, from the matter contained between the two sides of the fissure or dike, it is denominated a clay-dike, stone-dike, &c. II. A hitch is only a dike or fissure of a smaller degree, by which the strata on one side are not elevated or separated from those on the other side above one fathom. The hitches are denominated in the same manner as dikes, according to the number of feet they elevate or depress the strata. There are dikes (though they are not often met with in the coal countries) whose cavities are filled with spar, the ores of iron, lead, vitriol, or other metallic or mineral matters; and it is pretty well known, that all metallic veins are nothing else than what in the coal countries are called dikes. The strata are generally found lying upon each other in the same order on one side of the dike as on the other, as mentioned above, and nearly of the same thicknesses, appearing to have been originally a continuation of the same regular strata, and the dike only a breach by some later accident, perpendicularly or obliquely down through them, by which one part is removed to a small distance, and depressed to a lower situation than the other. But this is not the only alteration made in the strata by dikes; for generally to a considerable distance on each side of the dike, all the strata are in a kind of shattered condition, very tender, easily pervious to water, and debased greatly in their quality, and their inclination to the horizon often altered. III. Troubles may be denominated dikes of the smallest degree; for they are not a real breach, but only an approach towards t which has not taken a full effect. The strata are generally altered by a trouble from their regular site to a different position. When the regular course of the strata is nearly level, a trouble will cause a sudden and considerable ascent or descent: where they have, in their regular situation, a certain degree of ascent or descent, a trouble either increases it or alters it to a contrary position: and a trouble has these effects upon the strata in common with dikes, that it greatly debases them from their original quality; the partings are separated; the backs and cutters disjointed, and their regularity disordered; the original cubic and prismatic figures, of which the strata were composed, are broken, and the dislocation filled with heterogeneous matter; and the whole strata are reduced to a softer and more friable state. The strata are seldom, or never, found to lie in a true horizontal situation; but generally have an inclination or descent, called the dip, to some particular part of the horizon. If this inclination be to the eastward, it is called an east dip, and a west rise; and according to the point of the compass to which the dip inclines, it is denominated, and the ascent or rise is to the contrary point. This inclination or dip of the strata is found to hold everywhere. In some places it varies very little from the level; in others very considerably; and in some so much, as to be nearly in a perpendicular direction but whatever degree of inclination the strata have to the horizon, if not interrupted by dikes, hitches, or troubles, they are always found to lie in the first regular manner mentioned. They generally continue upon one uniform dip until they are broken or disordered by a dike, hitch, or trouble, by which the dip is often altered, sometimes to a different part of the horizon, and often to an opposite point; so that on one side of a dike, hitch, or trouble, if the strata have an east dip, on the other side they may have an east rise, which is a west dip; and, in general, any considerable alteration in the dip is never met with, but what is occasioned by the circumstances last mentioned. To illustrate what has been said, see fig. 2, where a b c d, &c. represents a course of strata lying upon each other having a certain inclination to the horizon. A B is a downcast dike, which depresses the strata obliquely to e f g h, &c. lying upon each other in the same order, but altered in their inclination to the horizon. CD represents a clay or free-stone dike, where the strata are neither elevated nor depressed, but only broken off and removed to a certain distance. E F represents a hitch, which breaks off and depresses the strata only a little, but alters their inclination to the horizon. GH represents a trouble, where the strata on one side are not entirely broken off from those on the other, but only in a crushed and irregular situation. As some particular strata are found at some times to increase, and at other times to diminish, in their thicknesses, while others remain the same, consequently they cannot be all parallel; yet this increase and diminution in their thicknesses come on very gradually. The strata are not found disposed in the earth according to their specific gravities: for we often find strata of very fense matter near the surface; and perhaps at fifty or even 100 fathoms beneath, we meet with strata of not half the specific gravity of the first. A stratum of iron ore is very often found above one of coal, though the former has twice the gravity of the latter; and, in short, there is such an absolute uncertainty in forming any judgment of the disposition of the strata from their specific gravities, that it cannot in the least be relied upon. From the foregoing sources we next give an account of the several strata of coal, and of stone and other matters, which are usually connected with coal, and are found to have a particular affinity with it: and shall arrange them into six principal classes, which include all the varieties of strata that occur in all those districts of country both in Scotland and England where coal abounds. I. The strata of whin-stone are the hardest of all others; the angular pieces of it will cut glass; it is of a very coarse texture, and, when broke across the grain, exhibits the appearance of large grains of sand half vitrified; it can scarcely be wrought or broke in pieces by common tools, without the assistance of gunpowder; each stratum is commonly homogeneous in substance and color, and cracked in the rock to a great depth. The most common colors of these strata are black, dark-blue, ash-colored and light-brown. Their thickness in all the coal countries is inconsiderable, from five or six feet to a few inches; and it is only in a few places they are met with of these thicknesses. In the air it decays a little, leaving a brown powder; and in the fire it cracks, and turns reddish-brown. Limestone, especially what is called bastard limestone, is sometimes, though rarely, met with in coaleries. It is well known, but, from its resemblance in hardness and color, is often mistaken for a kind of whin. Sometimes, particularly in hilly countries, the solid matter next the surface is a kind of soft or rotten whin ;-but it may be noted, that this is only a mass of heterogenous matter disposed upon the regular strata; and that beneath this all the strata are generally found in as regular an order as where the heterogenous matter does not occur. II. Post-stone is a free-stone of the hardest kind, and next to the lime-stone with respect to hardness and solidity. It is of a very fine texture; and, when broken, appears as if composed of the finest sand. It is commonly found in a homogeneous mass, though variegated in color; and, from its hardness, is not liable to injury from being exposed to the weather. Of this kind of stone there are four varieties; the most common is white post, which, in appearance, is like Portland stone, but considerably harder; it is sometimes variegated with streaks or spots of brown, red, or black. Gray post is also very common; it appears like a mixture of fine black and white sand; it is often variegated with brown and black streaks; the last mentioned appear like small clouds composed of particles of coal. Brown or yellow post is often met with of different degrees of color; most commonly of the color of light ochre or yellow sand; it is as hard as the rest, and sometimes variegated with white and black streaks. Red post is generally 1 of a dull red color; this is but rarely met with; it is often streaked with white or black. All these lie in strata of different thicknesses: but commonly thicker than any other strata whatever they are separated from each other, and from other kinds of strata, by partings of coal, sand, or soft matter of different colors which are very distinguishable. III. Sand-stone is a free-stone of a coarser texture than post, and not so hard; is so lax as to be easily pervious to water; when broke, is apparently of a coarse sandy substance; is friable and moulders to sand when exposed to the wind and rain; has frequently white shining spangles in it, and pebbles or other small stones enclosed in its mass. Of this there are two kinds commonly met with, distinguished by their colors, gray and brown, which are of different shades, lighter or darker in proportion to the mixture of white in them. It is, most generally, found in strata of considerable thickness, without many secondary partings; and sometimes, though rarely, it is subdivided into layers as thin as the common gray slate. It has generally sandy or soft partings. IV. Metal stone is a stratum, in point of hardness, next to sand-stone; generally solid, compact, of considerable weight, and of an argillaceous substance, containing many nodules of iron ore, and yellow or white pyrite; its partings, or the surfaces of its strata, are hard, polished, and smooth as glass. The most usual color of this stone is black; but there are several other lighter colors, down to a light brown or gray. It lies in strata of various thicknesses, though seldom so thick as the two last mentioned kinds of stone. V. Shiver is a stratum more frequently met with in coaleries than any other. There are many varieties of it, both in hardness and color. The black color is most common; it is called by the miners black shiver, black metal, or bleas. It is softer than metal stone, and in the mine is rather a tough than a hard substance, is not of a solid or compact matter, being easily separable, by the multitude of its partings, &c. into very small parts, and readily absorbing water. The substance of this stratum is an indurated bole, commonly divided into thin laminæ of unequal thicknesses, which break into long small pieces when struck with force; and, on examination, they appear to be small irregular rhomboids: each of these small pieces has a polished glassy surface; and, when broke across the grain, appears of a dry leafy, or laminated texture, like exceeding fine clay it is very friable; feels to the touch like an unctuous substance; and dissolves in air or water to a fine pinguid black clay. There are almost constantly found enclosed in its strata lumps or nodules of iron ore; often real beds of the same. Besides black, the brown or dun shiver is frequently met with. Gray shiver is also very common. It lies in strata sometimes of considerable thickness, at other times not exceeding a few feet; they are commonly parted from each other by lamine or spar, coal, or soft matter. VI. Coal. Referring the reader, for the scientific division of coals, to AMPELITES, LI THANTHRAX, and the preceding articles, we shall here consider them as distinguishable into three kinds, according to their degrees of inflammability. 1. The least inflammable kinds are Welsh coal, Kilkenny coal in Ireland; and blind or deaf coal, which last is found in many parts of Scotland and England. This coal takes a considerable degree of heat to kindle it, but, when once thoroughly ignited, will burn a long time; it remains in the fire in separate pieces without caking; it produces neither flame nor smoke, and makes no cinder, but burns to a white stony flagg; it makes a hot glowing fire like charcoal or cinders, and emits effluvia of a suffocating nature, which renders it unfit for burning in dwelling-houses, its chief use being among malsters, dyers, &c. for drying their commodities. 2. Open burning coal soon kindles, making a hot pleasant fire, but is soon consumed: it produces both smoke and flame in abundance; but lies open in the fire, and does not cake together so as to form cinders, its surface being burned to ashes before it is thoroughly calcined in the midst; from this it has its name of an open burning coal: it burns to white or brown ashes very light. Of this kind is cannel coal, jet, parrot, splint, and most of the coals in Scotland. 3. Close burning coal kindles very quickly, makes a very hot fire, melts and runs together like bitumen, the very smallest culm making the finest cinders, which, being thoroughly burnt, are porous and light as a pumice stone, and when broke are of a shining lead color; it makes a more durable fire than any other coal, and, finally, burns to brown or reddish colored heavy ashes. Of this kind are the Newcastle and several other of the English coals, and the smithy coals of Scotland. The open burning and the close burning coal mixed together, make a more profitable fire for domestic uses than either of them separate. In all those districts where coal is found there are generally several strata of it: perhaps all the different kinds above mentioned will be found in some, and only one of the kinds in others; yet this one kind may be divided into many different seams or strata, by beds of shiver or other kinds of matter interposing, so as to give it the appearance of so many separate strata. All these strata, with their several varieties, do not lie upon each other in the order in which they are described, nor in any certain or invariable order. Though there be found the same kind of strata in one coalery as in another, yet they may be of very different thicknesses. In some places there are most of the hard kinds, in others most of the softer; and in any one district it rarely happens that all the various kinds are found; for some kinds occur only once or twice, whilst others occur ten or twenty times before we reach the principal stratum of coal. To explain this, suppose the strata in the pit at A, fig. 3, lie in the order a, b, c, d, &c. they may be so much altered in their thicknesses by reason of some of them increasing and others diminishing, at the distance of B, that they may be found there of very different thicknesses; or if they are examined in a pit at D, by reason of its lower situation, and the strata there not being a continuation of those in the other places, they may be very different both in their order and thicknesses, and yet of the same kinds. Though they be thus found very different in one coalery, or district, from what they are found to be in another, with respect to their thicknesses, and the order in which they lie upon each other, yet we never meet with a stratum of any kind of matter but what belongs to some of those above described. To illustrate how the various strata lie in some places, and how often the same stratum may oc cur betwixt the surface and the coal, we shal give the following example. The numbers in the left-hand column refer to the classes of strata before described, to which each belongs. The second column contains the names of the strata ; and the four numerical columns to the right hand, express the thickness of each stratum in fathoms, yards, feet, and inches. In the following instance the species of sand-stone only occurs twice, and that of post five times, whilst the shiver curs no less than nine times. To apply the foregoing observations to practice: suppose it be required to examine whether there be coal in a piece of ground adjoining to, or in the neighbourhood of, other coaleries. It is proper to be informed, at some of the adjacent coaleries, of the number and kinds of strata; the order in which they lie upon each other; to what point of the horizon, and in what quantity, they dip; if any dikes, ditches, or troubles, and the course they stretch Having learned these circumstances, search in the ground under examination, where the strata are exposed to examination, and compare these with the other. If they be of the same kinds, and nearly correspond in order and thickness, and by lying in a regular manner, and agree by computation with the dip and rise, it may be safely concluded that coal is there; and the depth of it may be judged from the depth of the coal in the other coalery, below any particular stratum which is visible in this. II. If the solid strata are not exposed to view, either in the hills or valleys of the ground under examination, then search in the adjoining grounds; and if the same kinds of strata are found there as in the adjacent coalery, and there is reason from the dip and other circumstances, to believe that the stretch through the ground to be exa 25 mined, it may be concluded that the coal is there, as well as these other strata. Suppose a coalery is on the side of a hill at A, fig. 3, and you would search for coal at B, on the other side of the hill, but in a much lower situation; by observing the several strata lying above the coal at A, and the point towards which they dip, which is directly towards B (if clear of dikes), you may expect to find the same kind of strata on the other side of the hill, but much lower down. Accordingly if some of the strata are visible in the face of the precipice C, they may be compared with some of those in the pit at A. Or, if they are not to be seen there, by searching in the opposite hill, they may perhaps be discovered in the place F; where, if they be found in the manner before mentioned, and there be reason to believe they extend regularly from the first place to this, it is more than probable the coal, as well as these strata, will be found in the intermediate ground. III. If the ground to be examined lie more to the rise of the coal, as at E, which being supposed to be on a flat, perhaps the solid strata there may be wholly covered by the gravel, clay, &c. of the outward surface lying upon them: in this case, by measuring the horizontal distance and the descent of ground from A to F and computing the |