Leo Lesquereux

“ For the action of heat does not deprive the coal of any part of its constituents; it merely quickens the slow burning or metamorphosis of the matter, the ultimate result of which is the entire reduction of the oxygen- and hydrogen-producing volatile gas into compact or condensed mineral combustible, a mere compound of the original elements of wood modified under peculiar influences.—The great Alleghany coal field extends from the middle of Alabama to northern Pennsylvania, and occupies portions of Alabama, Georgia, Tennessee, Kentucky, West Virginia, Virginia, Ohio, and Pennsylvania. ”

“ In the transportation of trees or vegetable remains by water, a large proportion of sand, mud, &c., would of course have been swept down with the forests, and mixed in the deposits with the wood, rendering the matter very impure. Moreover, the coal deposits are generally in flat basins of wide extent, and an equal distribution of the trees in horizontal layers is an impossibility by transportation of this kind. Another difficulty in the amount of woody matter which enters into the composition of a coal bed is not generally known, and is far above every hypothetical calculation. ”

“ This is a great mistake, for indeed nothing but the growth of the materials upon the place where they have been buried and transformed into coal can satisfactorily account for the immense proportion of woody matter in the deposits. The comparative caloric power of wood, peat, and coal has been found to be on an average represented by the proportion of 30 for wood, 37 to 40 for peat, according to its age, and 60 for bituminous coal. We have seen above what is the average production of wood under the best regulated cultivation of Europe. ”

“ The analysis of caking coal fails to show any difference even in the proportion of the constituent elements from that of some kinds of dry or non-caking coal. Indeed, the character of the coal, where closely examined, is constantly variable in the same bed at the same mine, even upon the same square foot of matter, as recognized from specimens when taken at the same place from the roof to the bottom of the bank, although little or no difference is observed in a large quantity as it comes from the mine. ”

“ COAL, a black, opaque, inflammable substance, generally hard and compact, though laminated and stratified in beds between layers forming the crust of our earth. Coal has become one of the essential elements of modern civilization; in fact, the progress of the civilization of a country is now recorded by the amount of coal obtainable and employed by the inhabitants in a given time.—Mineral coal is a compound especially of carbon or of decomposed woody matter, with inflammable substances and hydrogen and oxygen gases. ”

“ When the materials which enter into the composition of peat are growing in a deep basin of water, and their debris are heaped under water, the preservation of the matter against rapid decomposition is then the direct result of immersion. ”

“ Peat is formed in shallow water or in bogs, by the growth of plants which may be called bog plants, and which belong to a peculiar group of vegetables composed essentially of woody tissue and living either in water or above water, according to local circumstances. The species of plants forming peat in our time do not thrive out of the bogs, neither do land plants invade the bogs and contribute by their remains to the composition of peat. ”

“ In connection with the coal strata, and in their roof shales, remains of fossil plants are found in profusion, indeed in the same position and in the same abundance as the remains of plants are seen in the true coal measures; but they represent far different species. With some ferns of a peculiar type, the fossil plants of the trias are mainly species of conifers, and in the greatest proportion species of cycadeæ, a family which is predominant also in the flora of the Jurassic period. Of this period, which in Europe is a formation of immense thickness, we have little in America. ”

“ The combustible matter is abundant enough to percolate through the fissure with water; it is also obtained from the shale by distillation. Even these black shales have been used for fuel, giving a bright flame, though they do not consume. They have been constantly searched for coal; but no coal has been found in this formation, which from its fossils is evidently of marine origin. With the bones and teeth of large fishes, it has also the remains of seaweeds to which its bituminization is due. ”

“ But nowhere has the land vegetation been luxuriant enough to produce coal, though the genera, if not the species, represented by these plants are closely allied to those of the carboniferous period. The upper Devonian, especially the Chemung, presents by its vegetable remains the same character as those of the former period; but the land vegetation becomes more and more predominant, yet not enough to produce coal. Moreover, most of the upper Devonian strata represent beach formations by their red shales. ”

“ The process of transformation of vegetable matter into peat is due to the presence of water, as is apparent from a consideration of the different modes of decomposition of vegetable matter as explained by chemistry. When wood is immersed in water and thus guarded against the action of the atmosphere or of the carbonic acid which causes its decay, it is preserved sound for a very long time. ”

“ The archæan rocks, also called primitive rocks, are therefore the only ones universally formed, all the others depending upon local abrasions for their materials, which, transported and deposited mostly by water, are local in their distribution. Animal life is now, and must have been from the beginning, dependent upon vegetable life as the only source of its food. The first traces of organic remains should for this reason represent plants. The primitive or archæan formations have deposits of graphite or plumbago, a matter essentially composed of carbon. ”

“ The amount of volatile combustible matter in its composition is extremely variable, and therefore its appreciable characters, either in its value as a combustible material or in its appearance, vary in the same degree, considerably blending the classification and multiplying its names. With a moderate proportion of inflammable gases it is dry coal; with more bitumen it becomes fat coal, which passes to caking coal when in burning the matter softens and coalesces like paste. ”

“ With some species of ferns of the coal measures, its flora is represented by large calamites, a genus whose species have the texture and outside form of the horsetail plants of our time, but of an immense size, and especially with new types of conifers. In North America the Permian formations are mostly composed of thick strata of magnesian limestone, overlying the upper coal measures of the west, near and along the Missouri river, especially in Kansas, and also in the Rocky mountains, where it generally underlies the cretaceous formation. ”

“ The presence of graphite in the carboniferous strata of Rhode Island, and the close likeness of some beds of anthracite of this basin, which in some of its veins is scarcely distinguishable from graphite, point to vegetables for the origin of this substance. For even the hardest layers of anthracite or graphite of Rhode Island bear well preserved remains of plants of the carboniferous period, and evidently their carbon has been derived from vegetable life. ”

“ Often the original form of the plants from which these woody fibres are derived (bark of lepidodendron, sigillaria, calamites, leaves and stems of ferns, &c.) is visible to the naked eye. In some cases a piece of coal a few inches square is seen with its faces covered with branches and leaves of ferns perfectly distinct in their outline and nervation; and in that way as many as five species have been identified upon the same surface, from their carbonized skeletons. In other cases, as in cannel coal, the fibrous texture of the matter cannot be recognized at first ”

“ In anthracite the amount of carbon is still increased, while that of hydrogen and oxygen has become proportionally less, and the volatile matter is reduced to a minimum. Hence pure anthracite is debituminized and burns without any flame. The anthracite of Pennsylvania becomes harder and more free from gas in proportion to the distance of the basins eastward from the Allegheny mountains, where its beds are folded in more numerous and sharper flexures. ”

“ Its growth is rapid; where more space is afforded, it extends its plants all around, covering the whole surface of the bogs and every kind of woody debris spread upon it. Its tufts go up the roots of the trees, and surround the standing trunks one to two feet high; they pass over the prostrate trees and their branches, and bury them under a thick carpet which preserves them against atmospheric influence. In foggy countries, as in Ireland and Germany, the sphagnum ascends steep slopes and builds its peat deposits from the plains to the tops of high mountains. ”

“ Indeed, in regard to the population of the gold-mining countries of the Rocky mountains, and to the building of railroads across the plains from the Missouri to the Pacific, the lignitic basin of the west is for the future as important as are for the present the Appalachian coal beds or the coal fields east of the Mississippi river. ”

“ By successive annual growth and deposits this groundwork becomes thick and more solid; shrubs and even trees take root and grow upon it, till the mass becomes too heavy, is split or torn asunder, and sinks to the bottom. Other series of vegetation may begin again in the same way and be successively heaped upon one another, peat beds and forests, till the basins are filled. From some of these filled lakes now discovered under thick strata of humus, peat and wood, and even large trees which could be used for building, have been dug out to a thickness or a depth of 75 ft. ”

“ The best coal produced in this field is from Indiana, where along the eastern border of it there is a good quality of block coal for furnace use, and some common bituminous coal of fair quality. The Illinois coal is all much inferior to that of Pennsylvania and Ohio, contains a portion of hygrometric moisture which lessens its heating power, and considerable sulphur and other injurious impurities. ”

“ At some localities, especially in the upper part of the measures, it is softer and more easily broken; but at others the matter is hard, compact, distinctly laminated in thin alternate layers of crystalline and more opaque matter, gives much heat by combustion, the best kinds in some localities, as at San Pete in Utah, even producing good coke, and when the beds are in proximity to upraised dikes of basalt or lava the coal is transformed into anthracite. ”

“ The limestone beds of the coal have rarely if ever remains of plants, but often a great quantity of animal remains, coral, crinoids, fishes, and especially shells. As will be seen hereafter, the distribution of all these kinds of strata is normal and explainable, as is also the formation of the shales, which are seen not only as the roof of the coal beds, but interlying them, and unfortunately sometimes in numerous alternate layers with which the pure coal is so closely mixed that these coal strata are not workable. ”

“ Nearly all the provinces produce both black and brown coal, or carboniferous coal and lignite. Russia has a large coal area, which like that of Scotland is subcarboniferous, or situated geologically below the formation in which the best coal of England and America is found. The only coal field of Russia belonging to the true coal formation is a small tract in Poland containing 80 sq. ”

“ The growth of the peat in cases of this kind may be stopped at the water level, where by a more complete decomposition of the plants a coat of humus is formed, which being invaded by land plants is transformed into a prairie or a forest.—But more generally peat grows above the water level, and then the production of the matter and its protection against the influence of the atmosphere are essentially due to the agency of a peculiar kind of moss, the sphagnum. ”

“ As free bitumen does not exist in nature, deposits of bitumen in the rocks are an anomaly as long as the origin of bitumen cannot be positively indicated. Moreover, there is a great difference between bitumen, or rocks impregnated with bitumen, and coal beds. Hardened or oxidated bitumen has been found in a few instances filling crevices of rocks, as in Canada and in West Virginia ”

“ The rocks all around in the country bear traces of metamorphism, and the change by heat becomes more and more evident in advancing toward the Hot Springs, a volcanic region, away from the mountains. The same phenomenon is still more evident, and its cause more appreciable, in the tertiary lignite basins of the Rocky mountains. At Golden, Colorado, the thick lignite beds, 12 to 16 ft., are thrown up to the perpendicular by compression, in close proximity to the base of the uplifted granitic mountains, and between them and thick deposits of lava. ”

“ Its thickness is rarely under 3 ft., more generally 6 to 7 ft.; at Straitsville in Ohio it is 12 ft.; it is 30 ft. or more in some localities of the anthracite basin of Pennsylvania. From the millstone grit upward, in a thickness of from 500 to nearly 1,000 ft., coal beds are formed of various thickness and extent, alternating with strata of shale, limestone, sandstone, &c., up to the great Pittsburgh coal, which is, near the end of the productive carboniferous formation, what the big vein is near its beginning. ”

“ The coal is all bituminous and of a fair quality for gas and steam purposes. There is also an unproductive anthracite coal field in Rhode Island and Massachusetts.—The foregoing fields comprise all the carboniferous coal in North America, and it is not probable that any other districts of any extent containing true coal will hereafter be discovered. ”