Popular Science Monthly/Volume 14/January 1879/Black Diamonds
By M. F. MAURY.
AS we sit by our firesides and peer into the glowing coals, or watch the bright jets of flame spring into existence to throw their cheery light into the room, making weird, fantastic shadows on the wall, and bringing with them such comforting cheer to our senses of sight and feeling, we are often brought into very reflective moods, especially if we are sitting in the twilight, while the cold wind is whistling, and the sharp snow and hail of winter are clicking against the windows. But how very few think, or care to know, whence comes this black substance that adds so much to the comfort and ease and luxury of life! Yet an account of its uses and its history and the story of its formation are instructive in the extreme, and as interesting as those two great subjects of the day—the telephone and the phonograph. Why the former excites so little comment, and the latter so much, can be easily explained, for we were born and raised with the blessings and comforts of the one, and they are of such every-day occurrence as not to excite attention; while the others, though less beneficial to the race, are so new and startling in their wonders, that they at once claim our thoughts and make us eager to learn of them and their progress.
There is no one substance in all Nature that has done more to ameliorate the condition of mankind, to build up the pride and strength of nations, to convert the world from barbarity to civilization, or add more to our ease and luxury, than this black and uninviting-looking mineral. Through its agency in producing the motive power for machinery in the steam-engine, the wild places of the earth are penetrated, men have ready and quick transit thereto, all the benefits of civilization flow in, cities spring up, the husbandman has facilities for sending his surplus produce to the markets of the world, and waste places are made to blossom like the rose. Those nations that possess it in the greatest abundance and purity are those that rise the most rapidly to the highest and mightiest positions; for it is the mainspring of all manufactures, and it carries the products of such to the consumers in distant countries, across the trackless waste of waters, with a certainty and speed unattainable by any other means; it enables nations to stretch forth their armies and navies with such promptness that insults are followed by speedy retribution, and invasion met or guarded against. The light for our homes and cities, the most beautiful and delicate dyes for clothing fabrics, and the ink that prints our books and papers to scatter knowledge through the world, all come from the products of its distillation. In all the power exercised by it, it works greater wonders than the magician's wand in the "Arabian Nights;" in its beneficial effects to mankind, it may be said, like mercy, to shed its gentle dews from heaven; and, by being the prime cause of annihilating distances, it has brought the human race closer together, and is thus the "one touch of nature that makes the whole world kin."
It is not only the most useful but it is the most valuable of all minerals, on account of the wealth that is produced through its agency. It is well understood that money is a sequence of work, and a community that has small labor-bills can take the trade away from those that have to pay high rates. Let us, therefore, see what work this substance can produce.
In mechanics the unit of work is the power necessary to raise one pound one foot high, and this is known as a foot-pound. From numerous experiments and observations, an able-bodied man, in working ten hours a day, exerts an average force of 1,000,000 foot-pounds. When coal is burned under a boiler it produces steam, which in turn produces work as it drives machinery. Therefore, coal produces work, the amount of which will vary according to the perfection of the machinery and the appliances for generating the steam. If we take an average of all kinds of engines, one pound of coal will produce steam sufficient to exercise a power of 500,000 foot-pounds. Hence the work accomplished by two pounds of the fuel equals a man's day's work. Now, mark the surprising results to which this leads us. The population of the United States is about 40,000,000, and in 1877 we produced 50,000,000 tons of coal. If one-fourth of this were applied to manufacturing, etc., it would do as much work as our whole population, assuming them all to be able-bodied men, in 350 days. The coal at the engine will average about four dollars a ton, while the price of unskilled manual labor can be put down at one dollar a day. Applying these figures, we see that the work in the first case would have cost $50,000,000; while in the latter, were it even possible to employ so many men, the labor-bill would have been $14,000,000,000! Can any one for a moment question the advantage or the value of the substance?
In these days, accustomed as we are to its multitudinous uses, it is difficult to imagine ourselves in the position of the early writers, who touched with uncertain pen on what they thought to be the leading characters of a rare and ambiguous mineral, or to conceive that its introduction was accompanied by such prejudice and superstition that laws were actually passed forbidding its use by the very countries that now consider it as the greatest of their possessions. In fact, it is of comparatively late date that it has sprung into the important position which it now occupies.
The earliest express mention made of it as a fuel was about 300 b. c., in the writings of Theophrastus, the pupil of Aristotle, who speaks of it as being found in Liguria (now the province of Genoa) and in Elis on the way to Olympias, where it was used by smiths. Ampelitis, a black stone "like bitumen," is mentioned by Pliny as available for medicinal purposes. It has been attempted to show that the ancient Britons used it, but there is no satisfactory evidence on the subject prior to the later days of the Roman occupation, and it is not until the thirteenth century that we obtain clear proof that it was systematically raised for fuel in England. In December, 1239, King Henry III. granted a charter for this purpose to the townsmen of Newcastle-upon-Tyne, and the coal soon found its way to London; but the complaints against it became so great, as it got to be more and more used, and the city more smoky, that in 1306, on petition of Parliament, "King Edward I. by proclamation prohibyted the burneing of sea coale in London and the suburbs to avoid the sulferous smoke and savour of the firing, and commanded all persons to make their fires of wood" (Stow). Nevertheless in about fifteen years it effected a lodgment even in the royal palace, for in 1321-1322, in the "Petitiones in Parliamento," a claim is made for ten shillings on account of fuel of that sort which had been ordered by the clerk of the palace, and burned at the king's coronation, but neglected to be paid for.
On the Continent of Europe the earliest coal known was in the tenth century, in the coal-basin of Zwickau in Saxony, but in 1348 the metal-workers of that town were forbidden to pollute the air with coal-smoke.
In England, in 1577, an old writer (Harrison), in contrasting the burning of coal in chimneys and of wood without them, alludes to this prejudice when he says: "Now we have many chimnyes, and yet our tenderlings complain of rewmes, catarres and poses; then had we none but reredoses, and our heads did never ake. For as the smoke in those days was supposed to be a sufficient harding for the timber of the house, so it was reputed a far better medicine to keep the good man and his family from the quacke or pose, where with, as then very few were acquainted. There are old men yet dwelling in the village where I remain, which have noted the multitude of chimnyes lately erected, whereas in their yoong days there was not above two or three, if so many, in the most uplandish towns of the realme, but each one made his fire against the reredose in the halle where he dined and dressed his meate." In 1632 the historian, Stow, remarks, that "within thirty years last, the nice dames of London would not come into any house or roome where sea coales were burned, nor willingly eat of the meate that was either sod or roasted with sea coale fire." In some parts of France the prejudice against the fuel extended even to within our own day—in 1840—for St. John, in his "Journal of a Residence in Normandy," mentions that Dr. Bennett, a Protestant clergyman, told him that "he had received orders to quit his house, because he burned coal; and another English gentleman at Caen, who had invited a large party, finding his drawing-room very thin, and inquiring the reason, found that the French had staid away because it was understood he burned coal."
These latter, however, are isolated cases, for we see that its economy as a fuel gradually beat down prejudice and opposition, and the consumption steadily increased; but up to the beginning of the eighteenth century the only purpose for which it was used was for the production of heat in houses. It was now to enter upon its second grand phase of usefulness—that for the generation of force, as manifested through the agency of the steam-engine, which was first used for mining purposes. By this application of steam not only was the mining of the coal made cheaper, but the facilities for distributing it enlarged, and as engines were improved from time to time, their number increased, because they could be economically employed in a greater number of industries, and therefore the demand for this class of fuel rapidly extended.
About 1805 light established a new market and demand for the black diamonds. For a hundred years or more there were various experiments on the distillation of coal in order to produce tar and oils, while the practical application of the invisible gases that were set free was not thought of till 1793, when William Murdoch, engineer to Bolton & Watt, employed coal-gas for lighting his house and offices, at Redruth in Cornwall. The earliest application of this light, on a large systematic scale, was in Manchester, where an apparatus for illuminating the cotton-mills of Messrs. Phillips & Lee was fitted up in 1804 and 1805, under the direction of Mr. Murdoch. This new invention rapidly spread, and in 1807 public streets were thus lighted. During 1877 the gas companies in New York City and the immediate vicinity alone required about 450,000 tons.
At Coalbrook Dale, in England, between 1730 and 1735, Abraham Darby made successful experiments in substituting coal for charcoal, in the manufacture of iron, in the blast-furnace, and thus made the first step in an industry that now requires millions of tons annually; though it was not till 1830 that this trade really began to assume the gigantic proportions which it now has. At that date Neilson, in Scotland, applied the hot-blast to iron-furnaces, for the purpose of economizing fuel, and succeeded so well that a ton of coal now reduces three times as much iron as it did before. This, like all other inventions tending to economy, increased the manufacture of iron, and consequently demanded more fuel, exactly as the merchant finds it to his advantage to have quick sales and small profits.
During the last twenty years chemistry has discovered many minor but none the less striking applications of coal in utilizing the once waste products of its distillation for gas. Among these may be cited solid paraffin, which, when made into candles, equals in beauty those of wax; from its analine are obtained many of the most exquisite dyes, whose shades and tints please the eye and gratify our tastes; it seems almost past belief that some of the delicate toilet perfumes come from it, and that flavoring extracts to pander to our palates are distilled from the same black substance.
In America it is remarkable that the first discovery of this mineral, of which we have any written record, should have been made as far in the interior as Illinois. It is mentioned by Father Hennepin in 1669, when he found the outcrop of a seam on the Illinois River, where the town of Ottawa now stands. The first that came into use, however, was that from Virginia, near Richmond, which for a long time supplied the whole Atlantic market. Anthracite (of which we produced over 21,000,000 tons in 1877) had quite a struggle to obtain a footing, as its value and use were not known; in fact, the first Lehigh coal sent to Philadelphia in 1803 was considered worthless, and was broken up to be used on the sidewalks.
In the early days of this country, wood was so abundant and cheap, and the means of transportation from the interior so limited, that the demand for fossil fuel in the United States could be met by a few thousand tons a year. We have no accurate record of the tonnage which was produced, but it was about 1,600 tons of anthracite and about 80,000 tons of bituminous in 1820, which was one ton to every one hundred and twenty persons of the population. As the country was settled, railroads built, furnaces erected, and steam and machinery came into greater and greater use, the demand increased, until in 1877 the production was one and a quarter ton to every man, woman, and child of the Union—or 50,000,000 tons. The vast quantity represented by these figures can be better brought before the mind by stating that, if this amount were packed in a solid mass, it would make a wall from New York to Washington—two hundred and forty miles—ten feet wide and eighty-five feet high; while, if it were put together in the broken state in which coal is commonly used, the wall would be one hundred and sixty-one feet high. This tonnage places our country as the second coal-producer in the world. Great Britain being first, with an output in 1877 of about 130,000,000 tons.
From what has been said regarding the power and wealth that this article bestows, the following table shows that the American Union has a most magnificent future prospect, as it is destined to become the great fuel-producer of the earth; and that not only because of the vast area of its coal-fields, but because of the thousands of square miles wherein the seams are so easily accessible to the miner; as they often lie either above water-level or at very moderate depths, thus obviating the expense of deep and costly shafts to reach them, and this is a very great advantage. "So immense indeed are the riches of the American coal-measures that, in their conception of the future development of mankind, geographers, historians, philosophers, agree in the idea that the United States have, especially in their coal-deposits, the elements for the greatest and most perfect development of the human race" (Lesquereux).
|COUNTRIES.||Area of Coal-fields in
|Percentage of Total|
|Chili, Australia, India, China, etc.||28,000||11.00|
And now for the story of how this wonderful mineral was formed. It is one of the well-established facts of geology that it is of vegetable origin. This is not simply a theory, for in Nature coal can be seen in various stages of formation where vegetable tissue is heaped up and accumulated in bogs. As we dig down into these bogs where the woody matter is surrounded by moisture, and in a favorable position for slow decomposition, it is seen that it is transformed into a dark, combustible compound which is first called peat; then, as it becomes harder and more changed, lignite; while the oldest peat-bogs in Europe have, at or near their bottom, thin layers of hard, black matter that neither examination by the eye nor analysis by the chemist can distinguish from true coal, and which, therefore, must be true coal. "In Holland, Denmark, and Sweden, the thick deposits of peat are separated into distinct beds by strata of sand and mud, giving the best possible elucidation of the process of stratification of the coal-measures" (Lesquereux). For their formation these bogs require a basin rendered impermeable by a substratum of clay and an active growth of aquatic or semi-aërial plants, having their roots in water, while their branches and leaves expand on the surface thereof, or rise in the air above it, constantly growing in the same place, whose débris, falling year after year, is heaped up and preserved against atmospheric decomposition by stagnant water or great humidity in the air. It was during the Carboniferous epoch, when our principal and most valuable seams of coal were deposited, that all these favorable circumstances were in their highest development. For a dense vegetation we also want a warm, moist, and equable climate, and air more or less charged with carbonic-acid gas, as that is the food of plants (just as the oxygen gives life to man), though it is poisonous to warm-blooded animals, it being impossible for such to live in an atmosphere containing more than about one per cent. of it.
During the Carboniferous age of the earth's history the water covered very much more of area than it now does, and portions of the continents were so little raised above its surface that a slight elevation or depression would change them from marshes and lagoons into dry land, or sink them below the surface of the sea. When air passes over, or rests on, oceans, or lakes, or rivers, etc., it becomes laden with vapor, whose influence is very potent, as its power of absorbing and retaining heat is thousands of times greater than that of air. Hence, as the ocean was so largely preponderant, there was an atmosphere heavily charged with moisture, which in time was favorable to a warm and equable climate. In fact, the want of annual rings in carboniferous plants proves that there was no winter, and, as the same coal-plants grew at the same time in Europe and America, the same climate must have prevailed. The air was also charged with carbonic acid, for there are no fossils (which Prof. Huxley so beautifully says are the labels that an Almighty hand has put upon the specimens in Nature's museum) in this or any other earlier formation of warm-blooded animals.
In all these circumstances, therefore, there exist the most advantageous conditions for the rapid and continuous growth of vegetation, and, judging from the fossils thereof, it must have gone on with a density and luxuriance that wellnigh surpasses conception. Floating vegetables first made their appearance, spreading their branches and leaves on the surface of the water, and filling the basin or lagoon with their débris thus forming a support for the more aërial vegetation, compared with which anything in our day of the same species, in respect to size and quantity, fades into insignificance.
The exuberant growth of the tropics is astonishing to us; but it is as nothing when we contemplate that of the coal era. For example: Equisetum, the horse-tail flag, with us is never more than half an inch in diameter, while in the coal-rocks gigantic reeds of this kind were as much as fourteen inches in diameter. Living club-mosses, even in our tropics, attain no great height, but there they were as thick as a man's body and sixty and seventy feet high. Our ferns are of insignificant size, but in those olden days they raised their feathery foliage to a height of sixty feet and upward. There are others that grew to the same wonderful proportions; and as they fell others sprang up, and thus the "heaping" process continued until Nature caused some subsidence of the ground; the water closed over it all, and the currents deposited mud and sand upon it: if the former, a stratum of slate was the ultimate result; if the latter, a stratum of sandstone. 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.
If, on the other hand, an elevation took place, the roots of the plants were deprived of their moisture, and they not only ceased growing and the deposit accumulating, but the rains and surface-drainage gradually eroded the latter away, and, as it floated off, it became mixed with any earthy matter which the waters may have had in mechanical suspension; and, when it was finally deposited in some lagoon or over-spread other formations, it ultimately made an inferior coal, or a black slate, according to the preponderance of the mud which was with it. Thus we can understand one of the causes why some regions have more seams than others.
When the deposit was covered up, as before explained, a gradual decomposition took place, which consisted in an evolution of a portion of the carbon, and most of the hydrogen and oxygen, in the form of water and gases from the woody tissue, leaving a larger and larger percentage of the carbon of the plant behind, while the increased pressure of the accumulating strata above served to compress and solidify the mass. But before this solidification took place, as Liebig has proved, by direct experiment in the process of slow decomposition of vegetable matter in water, a softening occurred, and it is to this that we must ascribe the fact that no delicate fossils are ever found in the coal itself, as the tissue and form were destroyed by the softening and subsequent pressure, though cases are met with where solid trunks of trees have resisted this softening process, and are found standing erect in the seams while their roots are plainly traced in the clay-slate below. In the slates above and below, which, it must be remembered, were originally soft, plastic mud, the plant-impressions, however, are as sharp and clear as though they had been sketched with an artist's pencil.
The formation of different kinds of coals, such as anthracite, semi-anthracite, semi-bituminous, and the many different varieties of bituminous, is supposed to be owing to the different degrees of progress made in the process of softening and carbonization, and to there having been freer escape for the gaseous constituents in some cases than in others. Chemists have actually converted vegetable matter into coal of all degrees of hardness, and possessing all the various qualities of that formed by Nature, and observation and their labors seem to show that all coal was first formed of the bituminous variety, and that anthracite is the result of igneous action to which it was subsequently subjected (MacFarlane). When this change has been carried still further, the result is plumbago, or black-lead.
I have thus endeavored to set forth in a plain, comprehensible manner the theories of the formation of our fossil fuels, and, while difficulties may suggest themselves to the reader, still that they are derived from the vegetable kingdom admits of no doubt, this being one of the well-established facts of geology.
There is one more benefit that coal has been the cause of bestowing upon mankind that is as striking as all those previously set forth, to which I would call attention before closing. The Bible tells us that the beasts of the field and the fowls of the air were not created until after the earth brought forth grass, the herb yielding seed, and the fruit-tree yielding fruit after his kind; and with the aid of science we can see a reason for this. It has been stated that one of the requisites for the vegetation of the coal era to flourish as it did was that the atmosphere should be charged with a compound of carbon and oxygen known as carbonic-acid gas, and that this gas, except in very small proportion, destroys life in warm-blooded animals. It was the tree that drank in the noxious vapor through its leaves, decomposed it, took of the carbon to add to its stature, and to yield seed and fruit after its kind, while it breathed the life-producing oxygen back into the air, and in this way the atmosphere was purified for the use of man and beast.
Thus in the economy and wonderful working of Nature not only was this gas, that precluded life, removed, but it was stored up for the future use of that same life that its removal made possible, so that coal, besides giving light and warmth, and a thousand other material blessings, was the prime cause of the very air we breathe. Surely it is, and it has been, a wonderful and blessed boon to the earth and its population, and it is of no wonder that it has been given the name of the most costly gem we know when it is called black "diamond."