Coal bed

“ It may very well be doubted whether any single bed of coal is ever more than two or three feet in thickness, and we may therefore take it for granted, that every bed which exceeds that thickness over any considerable space is in reality a compound seam made up of two or more beds resting on each other, with or without "partings" of shale, &c, between them. Not only then are many of the beds which are spoken of under one name in the southern part of the district compound seams, but several of those in the northern district also. ”

“ When this subsidence ceased, fresh growths sprang up and a new deposit was formed, to sink and be covered in its turn; and as often as these periods of rest and submergence were repeated, so often did a new coal-bed come into existence, and in this is a simple rational explanation why the coal-measures have more than one seam in them. ”

“ We were firm believers in variation of intervals between coal beds, but were not prepared for the variations which had been accomplished in the deeply buried portions of the section within northern Greene and southern Washington and which were revealed under an anticline in Washington. The imperfect record of a coal shaft reaching the Pittsburgh coal bed removed all doubts and filled us with intense respect for such records. ”

“ Changes also occur in the quality and character of coals, so that sometimes, the very same bed or part of a bed, may within a comparatively short space become so altered in quality as to form quite a different variety of coal, and, of course, be no longer recognizable as the same, unless it be actually traceable by continuous working from one locality to the other, or can be referred to continuously traceable beds above or below it. ”

“ The first coal forms the ninth bed from the surface, at the depth of one hundred and two feet, and is not more than four inches thick: it is very sulphurous. In the space between this and three hundred and ninety-six feet, lie nine other beds of stinking coal, none of which exceeds the thickness of seven inches except the lowest, which is a little more than a foot and a half thick. The first bed that is worked is a live-foot coal at the depth of four hundred and ninety feet, between which and the big-flint sandstone, already mentioned, are a ten-inch and a yard coal. ”

“ After the bed of coal is struck, ‘rooms’ are worked out, leaving ‘pillars’ or ‘stoops’ to support the superincumbent strata. The object to be attained in this system, as practised in the olden times, was to have as large a room worked out, and as small a stoop or pillar of the coal itself left, as was consistent with the safety of the mine and the support of the surface, while the mine was open. ”

“ A bed or seam of coal is, in fact, an aggregate of many successive deposits of vegetable matter. Under almost every bed of coal, as Mr. Logan in particular has shown in South Wales, is a peculiar fire-clay, or a fine-grained sandstone (ganister in Yorkshire) traversed by the rootlets of a plant (stigmaria) : over some beds of coal stand erect the stems of sigillaria and lepidodendron; and finally, at Dixonfold, near Manchester, and in other places, lepidodendra and sigillariæ rise erect out of a bed of coal, the former being connected below with roots which are stigmaria. ”

“ But even the merest business man will comprehend its utility, if he be interested in coal mines and can assure himself that the recognition of certain forms in one particular coal bed is likely to aid him in identifying that particular coal bed in other localities. ”

“ Indeed, so many things were spilled and dropped upon the bed that toward night-time it had become a sort of small cooperative store. Coal was what it always had most in stock. We used to keep our coal in the bottom part of the cupboard, and when any was wanted we had to climb over the bed, fill a shovelful, and then crawl back. It was an exciting moment when we reached the middle of the bed. We would hold our breath, fix our eyes upon the shovel, and poise ourselves for the last move. The next instant we, and the coals, and the shovel, and the bed would be all mixed up together. ”

“ When, however, the accumoulation of the vast quantity of vegetable matter necessary for the production of the Thick coal was nearly completed, a very partial and local subsidence took place in one or two localities, bending down the previously formed beds into a hollow or pool of water, sufficiently deep for 128 feet of shale and sandstone to be accumulated, and thus another level floor formed for the growth of the upper bed of coal, which grew partly on the shale and sandstone, and partly on the undepressed coal. ”

“ It is well known that, under present methods of mining, from 10 to 75% of any given deposit of coal is left underground as props and supports, or as low-grade material, or in overlying beds broken up through mining the lower bed first. An average of 50% of the coal is thus wasted or rendered valueless, as it cannot be removed subsequently because of the caving or falling in of the roofs of abandoned galleries and the breaking up of the adjoining overlying beds, including coal, floor, and roof. ”

“ Experience has taught that there are no coal seams below the conglomerate, so that wherever this is found as a surface rock, or wherever it is pierced by the drill, it is usually unnecessary to explore below it. If no coal outcrop is found, the bed of a stream is searched for fragments of the mineral, and, if any are discovered, they are traced to their source. Coal is sometimes exposed where [77] a tree has been uprooted by the wind, and pieces of it have been found in the soil thrown out at a groundhog’s burrow. ”

“ We then get two beds of coal, (Nos. 4, 5, and 6,) 71⁄2 feet thick together, including 8 inches of fire-clay between them, over which are 54 feet of alternations of fire-clay, clunch, binds, and rock, and then another bed of coal 9 or 10 feet in thickness. It is clear, nevertheless, from their position above the Heathen coal, that these latter coals, namely, No. 6, the "Bentley Hey," and No. 2, the "Old man's" coal, notwithstanding their being 54 feet apart, must be the representatives of the lower beds of the Thick coal. ”

“ These deposits are in the form of a thick bed of coal which has been opened up by modern industry which has cast aside as useless the blocks on which are preserved the priceless relics of the creatures of this bygone time. There have been great numbers of these blocks of coal collected by geologists, but in all probability the greater part of the animal remains preserved in the coal has gone to furnish heat for the people of the region. ”

“ It has been ascertained that some coal-seams must have originated from the deposition of drift-wood in the mud and ooze of the sea-bottom, while others undoubtedly arose from the decay and entombment of vegetation in swampy plains of the land. That the latter mode of formation has been the usual one in most of our coal-fields has been generally acknowledged since Sir William Logan's announcement that each coal-seam, for the most part, rests upon a bed of fire-clay, which, with its embedded roots, marks the site of an ancient soil. ”

“ Coal beds exist in Europe, Asia, and America, and have hitherto been esteemed as the most valuable of mineral productions, from the important services which the substance renders in manufactures and in domestic economy. It is to be remarked, that there are some local variations in the arrangement of coal beds. In France, they rest immediately on the granite and other primary rocks, the intermediate strata not having been found at those places. In America, the kind called anthracite occurs among the slate beds, and this species also abounds more in the mountain limestone than with us. ”

“ The first general section will include the mention of every workable bed of coal and ironstone in its proper place in the series, without regard to the locality in which it occurs. The second, while it agrees pretty nearly with the first in the lower measures (since each includes the Bentley district) , will exhibit in the upper part the change before alluded to as occurring in the grouping of the coals forming the Thick coal, as well as some other changes in the lower beds. ”

“ Their actual contents have not yet been gauged, but there is every reason to believe that those coal-beds which have been seen are but samples of many others which will, when properly worked, satisfy the needs of a much larger population than the country now possesses. ”

“ He, knowing that true faults when found in one bed must necessarily affect all the beds above it up to the surface, and looking at this gap in the Thick coal as a fault, expected to meet a similar gap in the Brooch coal above. ”

“ In the United States there are about 120,000 square miles underlaid by known workable coal-beds, besides what yet remains to be discovered; while on the cliffs of Nova Scotia the coal-seams can be seen one over the other for many hundred feet, and showing how the coal was originally formed. ”

“ Fig. 70 gives an idea of the ordinary arrangement of the coal-beds, one of which is seen interstratified between two parallel and nearly horizontal beds of argillaceous shale, containing nodules of clay iron-ore—a disposition very common in English collieries. The coal-basin of Aveyron, in France, presents an analogous mode of occurrence.
Fig. 70.—Stratification of coal-beds.
The frequent presence of carbonate of iron in the coal-measures is a most fortunate circumstance for mining industry. ”

“ A large proportion of the iron furnaces in this country, and nearly all of them in Great Britain, employ mineral coal for fuel, and obtain their ore from the beds contained in the coal measures.
The fossils of the coal measures are almost entirely of vegetable origin, and are very abundant. They are seldom found in the coal-beds, but in the strata of shale immediately above or below the solid coal. ”

“ Each upheaval, however, could have been but a temporary arrest of the great movement of crust subsidence which was going on throughout the coal period, so that, at its close, when the last coal forest grew upon the surface of the land, there had disappeared, in the case of South Wales, a thickness of 11,000 feet of material.
Of the many remarkable things in connection with coal-beds, not the least is the state of purity in which coal is found. ”

“ The richest part of the field in amount of coal-beds, both absolutely and still more in proportion to the whole thickness of the measures in which they lie is between Wolverhampton and Bilston, where the lower coals are becoming rapidly thicker, and the Thick coal is still nearly unbroken and undiminished. ”

“ The lower beds of the independent coal formation are here thrown up to an angle of 26°, the yellow sandstone adjacent being nearly horizontal, and in no place exceeding an inclination of eight or ten degrees. The coal beds have been lifted up by and repose anticlinally upon the trap, where the cutting for the road has exposed the outcrop of the seams; and thus, in a narrow space and lying on the surface, we may mark the outgoing and the incoming of a vast revolutionary epoch, organic and inorganic, in the earth’s history. ”

“ There is indisputable proof, however, that all coal beds are of vegetable origin. Geologists tell us that these coal beds were formed during an age before the earth had cooled down to the temperature that it has at the present time—an age when vegetation was forced by the internal heat of the earth instead of having to receive all its warmth from the sun's rays as we do now. Some of our readers are familiar with what is commonly termed a hotbed. A hotbed is made by putting soil on top of substances that will ferment and create heat underneath the soil. ”

“ Such are the separate chapters in the history of the coal-basins of Illinois, Missouri, Pennsylvania, New England, and Nova Scotia. First inland seas, then fresh-water lakes, then spreading marshes, then gigantic forests, and lastly vast storehouses of coal for the human race.
Although coal-beds are by no means peculiar to the Carboniferous period, since such deposits must be formed wherever the decay of vegetation is going on extensively, yet it would seem that coal-making was the great work in that age of the world's physical history. ”

“ In considering the formation and structure of the better-known coal-bearing beds of the carboniferous age, we must not lose sight of the fact that important beds of coal also occur in strata of much more recent date. There are important coal-beds in India of Permian age. There are coal-beds of Liassic age in South Hungary and in Texas, and of Jurassic age in Virginia, as well as at Brora in Sutherlandshire; there are coals of Cretaceous age in Moravia, and valuable Miocene Tertiary coals in Hungary and the Austrian Alps. ”

“ The demand for increased accommodations has rendered it necessary to fit up two of the original coal-rooms for dining-rooms, and to use the remaining two as work-shops, and for some years it has been necessary to deposit the most of the coal used in heating the house, in a huge, unsightly pile a short distance outside of the windows of patients' rooms. By using the foundation walls of the house for two sides of the vault, it is estimated that convenient storage-room for 500 tons of coal can be secured for the moderate amount of the estimate. ”

“ Should the coal be worked on the stoop-and-room system, and pillars of coal of sufficient size be left in, the surface will not be injured to any appreciable extent, at least not for many years. As is often the case, however, seams of coal are worked out one below the other; and when the lower one gives way, the pillars above may fall like a pack of cards. There is no saying where the subsidence would reach in such a case. If the pillars do not break, the way in which the ‘rooms’ close up, if the floor is soft, is rather peculiar. ”