Popular Science Monthly/Volume 18/March 1881/A Piece of Coal

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A PIECE OF COAL.
By R. S. CALVIN.

A LUMP of coal—black and grimy, and repulsive to sight and touch as it is—is, perhaps, not the most promising subject that could be selected for Sabbath-evening reflections. But, if there are sermons in stones, why not in coal? The black thing, that we would rather not handle when we have any proper regard for cleanliness, becomes an object of interest when we find it exerting energy in the engine-furnace or shedding warmth and radiance around our household hearth. It becomes an object of yet greater interest when we come to learn its wonderful history; for every common bit of coal that we are accustomed to see has a history with which is wrapped up the story of one of the most interesting and critical periods in all geological time. It is the lessons and promises of this far-off history of the coal that constitute the theme for to-night.

Fifty years ago an attempt to tell the history of the coal would, no doubt, have seemed, to all but a very few, not only hopeless, but absurd. Since then the methods of questioning Nature and making her tell her own history have been so much improved, and have been, withal, so energetically applied, that very much, which our grand-fathers would have set down as past finding out, has become the mental property of every well-instructed schoolboy.

There are many different kinds of coal, and coal belongs to many different epochs in the world's history, but that which we find in the coal-fields of Iowa and Illinois may be taken as the type of what is usually understood, the world over, when coal is mentioned. Let us fix our attention on a piece of such coal. To extort from that expressionless thing any facts bearing on its history would seem discouraging enough. We may look at it just as long as we please; we may break it to pieces with the hammer and examine it bit by bit, and it is altogether likely that we will be left just as wise and just as hopeless as when we began. Pass it over to the chemist, and he will tell us that it is made up of combustible matter of which so much is fixed and so much volatile, with a certain percentage of earthy substances and traces, perhaps, of ever so many elements that we never heard of before. The information is interesting—in many respects it is of the highest importance—but for the purposes of the present discussion it amounts. after all, to telling what men have more or less clearly perceived for the last thousand years or more, that coal will burn. By proper manipulation we may obtain thin slices of coal suitable for microscopic examination, and in this way may demonstrate that a large proportion of it is composed of what seems to be crushed and flattened vegetable cells. You are all aware that plants of every kind are made up of little microscopic units called cells, and that these cells differ so much in markings and other characteristics in the different groups of plants that one group may often be distinguished from another by the study of the smallest microscopic fragments. Now, in the coal itself, and often in the ashes that remain after combustion, it is possible to

PSM V18 D629 Lepidodendron modulatum and diplodigioides.jpg
Fig. 1.—Lepidodendron modulatum. Fig. 2.—Lepidodendron diplotigioides.

recognize the peculiar cells that characterize certain great divisions of the vegetable kingdom; and, as this method of study is extended, we are gradually led to the conclusion that coal has somehow been derived from plants. Let me say, however, that to reach a conclusion and to entertain an opinion on a question of this or any other kind, where matters of fact are involved, is too serious a thing to be accomplished lightly. The color, hardness, and other physical properties of coal, together with the fact that coal-beds are often buried under hundreds of feet of rock and soil, may well make us hesitate before accepting any such conclusion. Let us attempt the solution of the question in another way: All around the globe, in the middle and higher latitudes, are beds of peat. Now, peat, especially when well pressed and dried, presents many very suggestive resemblances to coal. But there is not the slightest difficulty in determining how peat is formed, for we may see the process going on before our eyes. We can study every stage in the process, from the living and dead plants growing and accumulating in the marsh at one end of the series, to the completed peat-bed awaiting only the proper manipulation to be converted into useful fuel at the other. That peat is formed of plants, and largely of plants that accumulate just where they grow, can be no longer questioned.

In the swamps and bayous of the moist regions of the South, pure vegetable matter, having the appearance and properties of peat, may often be found in the very act of accumulation. It frequently occurs in immense beds, and it requires no trained observation to see that, in addition to the remains of the ordinary low marsh-plants, it is made up of the ruins and refuse of swamp-loving forest-trees. Now, all about the flanks and spurs of the Rocky Mountains, with greater or less intervals, from New Mexico to far beyond the northern limits of the United States, there are found beds of coal of peculiar quality. This coal is covered up with hardened mud containing shells and bones of aquatic animals, and everything about it suggests that the coal-making materialPSM V18 D630 Restoration of a lepidodendron.jpgFig. 3.—Restoration of a Lepidodendron. was somehow sunk beneath the waters of an old lake, and was buried under the gradually increasing bed of mud with which the old lake-basin was finally filled. But the point of interest is this: that in many places the Rocky Mountain coal has reached a stage of decomposition not so very much in advance of the humus and peat of our modern swamps and bayous. We might, indeed, hesitate about calling some portions of it coal at all—for the original structure is almost perfectly preserved—yet it must be admitted that for the most part the decomposition has advanced far enough to produce an article that deservedly ranks as coal. In the light of what may be observed going on in every favorably situated swamp to-day, the source of the material and the method of accumulation of the Rocky Mountain coal can hardly be doubtful. I need not weary you by leading you step by step through all the known coal-fields that illustrate the different stages in the process of coal-formation. It will be sufficient to say that a perfect gradation may be traced from the lignite, as it is called, of the Rocky Mountains to the purer and more perfect coal of the Mississippi Valley; and so, even setting aside the internal evidence of our Iowa coal, we are compelled to believe that it is simply one of the terms of the same series to which the lignite and the peat belong, and that the initial term of that series is to be looked for in the living vegetation of modern marsh and forest.

The conclusion is interesting, though to an intelligent audience it could hardly be called unexpected. The method of reaching it is worthy of notice, and points some important lessons. Though the coal of Iowa was accumulated in what is called the Carboniferous age an age of the world that is immensely distant from the present, infinitely so, indeed, as we count time yet the processes of Nature were the same then as now. That old world was, in every essential particular, the same world that we know, and was governed by precisely the same laws that control it to-day. What is true of coal is also true of every part of the geological record to this extent: that all the strangely fascinating history recorded in the rocks must be read in the light of what may be seen actually taking place now. It has become a maxim of geology that, if we would know how anything was done in the past, we must study the method in which Nature is doing that very same thing in the present. Following these suggestions a little further, we are led from the study of this particular side of the history of coal, through similar studies, to the grander and more significant

PSM V18 D631 Sigillaria reticulata and graeseri.jpg
Fig. 4. Sigillaria reticulata. Fig. 5. Sigillaria Græseri.

generalization that the laws that govern the world have been the same for all time; that the laws of matter were imposed upon it as long ago as that old, old nebula of which you have heard, and that there has been no occasion to repeal the old or enact any new laws since.

But we must get back to our coal, and pursue the series to which it belongs a little further. The product of our Iowa mines is one of the terms, as we have seen, in that interesting series, but it is not the final term. We may start with bituminous coals, like those of Iowa, at Pittsburg, for example, and working our way across the State of Pennsylvania toward the foot-hills of the Alleghanies, we will cross one of the grandest coal-fields in the world, and at every stage of progress will pass from more to less bituminous coal, until by almost imperceptible gradations we will find ourselves in the region of anthracite. Anthracite, then, is only another term in the coal series; it represents only a more advanced state of carbonization than bituminous coal; the difference seems, in some way, to have been brought about by the play of the gigantic forces that gave rise to the mountains, for in all the region disturbed by those forces—in all the region in which the rocks have been folded and crumpled and changed—the coal is anthracite, and anthracite rarely occurs in other situations.

PSM V18 D632 Restoration of sigillaria.jpg
Fig. 6.—Restoration of Sigillaria.

Passing over the Alleghanies, we find the disturbing forces have acted with even greater energy on their eastern side, and accordingly in many places the only thing that bears any resemblance to coal is a black substance more perfectly carbonized than anthracite. It is to this substance that we are indebted for the universal use of the lead-pencil, for it is nothing less than black-lead or graphite. And here in a measure we lose track of our series; we find no gradations by which to trace it further, and yet it is as certain as anything can be that graphite is not the ultimate term, for in it we have not yet reached the perfection of carbonization. That perfection is finally reached, however, in the gem of gems, the diamond, the only example of absolutely pure, crystallized carbon. Though the steps between graphite and diamond are not known, we feel sure that those steps, or something corresponding to them, have been taken some time, and that diamond, graphite, coal, peat, and growing forest, all belong to the same series, and represent different conditions of the same thing. And so oar piece of coal acquires interest and dignity, and becomes, altogether, a thing not to be lightly despised, for, in addition to its own real worth, it enjoys the advantage of being able to claim kindred with the aristocratic Koh-i-noors of Golconda.

But how are the great ledges of rock above the coal to be explained? Let us see. The rocks in question are very often sandstone, and if we examine them carefully we find that they are spread out in layers, that they contain the remains of many marine animals, and that the surface of a very large number of the layers shows signs of having been washed by waves. With the exception that they are somewhat harder and the organic remains belong to more old-fashioned types, these rocks are exact duplicates of the widely spread layers of sand that the ocean is piling along all our shores to-day, and contain the clearest evidence that they have been swept into place by the waves of some old sea. But how came the coal beneath the sea? That is an important question, and the full answer to it would show that no truth is more plainly taught by all the records of the past and present than that the earth's surface is a very uncertain and unstable affair. You will find your answer to the question on the shores of Greenland,PSM V18 D633 Stigmaria ficoides.jpgFig. 7.—Stigmaria ficoides. where the coast, for hundreds of miles, is slowly sinking into the sea; the result in historical times being sufficient to convert old marshes into shallow bays over which sands are swept by each returning tide. You will find your answer along the coast of New Jersey, in the buried forests with their prostrate trees and upright stumps, all carried down in very recent times by the subsiding land just within reach of the sea. You will find your answer in the buried forests of the delta of the Mississippi. You will find the same answer m a hundred other places. Large areas of land in different parts of the world are gradually subsiding, and large areas in the Carboniferous age sank down in the same way. Each coal-seam is the record of peat-bog and forest; the overlying rocks record a period of submergence.

But the movements in the earth's surface at present are not all downward; there are, perhaps, as many cases in which the land is rising. During the Carboniferous age, the same thing was true, and it often happened that the area that was carried beneath the sea was, in time, reëlevated, and became the platform on which other forests and peat-bogs renewed the work of coal-making. Thus it is that in many coal-fields we find a number of seams, one above the other, and thus it is that we have registered in the coal-beds of Nova Scotia not less than seventy-six distinct upward and downward movements of the surface. The sinking of the old marsh beneath the sea might seem to involve the loss of all the materials that had been accumulating during periods, perhaps, for which years would furnish no adequate unit of measure, and yet this very movement was essential to the preservation of the great magazines of energy on which human progress so much depends. I have already referred to it as a matter of considerable interest, that a large proportion of some coal is made up of crushed vegetable cells; but that is not all—a still more wonderful fact remains to be noticed: The microscope, prying into all the little corners and secret places of Nature, declares that the pitchy parts of most bituminous coal are composed almost entirely of little spherical bodies, microscopic in size—so minute, indeed, that hundreds of them together might well be disregarded as "the small dust of the balance"—and yet so numerous that great coal-seams often appear to be made up of little else. Large numbers of them are often found huddled together in small round sacs

PSM V18 D634 Lepidodendron compared with club moss.jpg
Fig. 8.—Lepidodendron compared with Clue-Moss: a, club-moss; b, a scale enlarged; c, microspores; d, macrospores; x, lepidostrobus; y and z, the scales containing spores; m, microspores; n, macrospores.

of peculiar appearance. We are indebted to the patient labor of a number of observers for the fact that the smaller granules are the spores or seeds of some plant of inferior organization, and the larger sacs are fruit-cases in which the spores were developed. The whole history of this fruit, the manner in which it was produced, its relation to the stem and leaves of the plant to which it belongs, even its fertilization and development, have all been carefully worked out with an amount of labor that can hardly be appreciated, but with results as certain as if the actual development had been watched in the living plant.

The plants, themselves, on which this old coal-producing fruit was borne, and whose carbonized stems and leaves lie heaped up and mingled with the spores, have some lessons of interest for the student of world-history. One of the best known of these plants has been called Lepidodendron, or scale-tree, on account of the beautiful scale-like markings impressed upon the bark (Figs. 1 and 2). These markings diamond-shaped and arranged in close-set spiral lines around the stem—are scars left by the falling leaves. Elaborately sculptured stems are found in all our coal-measures, often with dimensions indicating trees three to five feet in diameter, and seventy to a hundred feet in height. Such trees, judging from their abundance and world-wide distribution, must have been conspicuous objects in all the forest-covered swamps of the coal age. Conceive, if you can, of tall, rigid trunks, ornamented with delightful patterns of inimitable sculpture-work, rising to a height of thirty or forty feet and these dividing into two equal clumsy branches; then let each of these divide again and redivide until a number—though not a very great number—of smaller branches are produced; then clothe each of the branches with a bristling array of thick-set, lance-like leaves; let each branch terminate in a club-shaped cone or fruit from which multitudes of resinous-spores, at the proper seasons, came showering down, filling the air with clouds of dust for days and weeks together, and sifting in among the roots of all the dense undergrowth with which the coal-marsh is covered—and, having drawn this mental picture fairly, you will have some idea, perhaps, of a Lepidodendron (Fig. 3).

But, if we would award credit where credit is due, we must in all fairness acknowledge the preeminent importance of another group of

PSM V18 D635 Ideal section of a sigillaria stem.jpg
Fig. 9.—Ideal Section of a Sigillaria-Stem: a, pith; b, woody cylinder; c, inner bark; d, rind; e, bases of leaves; f, vascular thread running to the leaves; g, medullary rays.

plants to which we are indebted for by far the largest share of the coal. These plants outnumbered the Lepidodendrons in all the swamps; like Lepidodendrons, they rose to the dignity of great trees; the trunks were composed of firmer and more densely packed woody tissue; the bark was thick and rich in bituminous matter, and in some of them it seems probable that large nut-like fruits were produced in place of spores. They are known as Sigillarias, and differ from Lepidodendrons, in addition to the characters already enumerated, in having stems loss frequently branched; the stems are also longitudinally fluted like some great columns of architectural beauty and finish, and between each pair of vertical ribs are now found the leaf-scars in variable but always orderly arrangement (Figs. 4, 5, 6). Instead of at the ends of the branches, the fruit was borne in cones, resembling pine-cones, springing from the sides of the stem. The leaf-scars often resemble impressions made upon wax by the old-fashioned seal, and hence the name Sigillaria, or seal-tree. Great, somber, stiff, post-like things they must have been, as, crowding each other in all the swamps, they lifted to the sky their great, bald trunks, with scarcely any branches, and nothing worthy of the name of foliage. Perhaps we should say that the most important part of Sigillaria was really underground, for all the old coal-swamps seem to have been traversed in every direction with a perfect network of creeping subterranean or subaqueous stems, and from these arose the aërial fruiting stems that we have called Sigillaria. Such underground stems, creeping and interlacing through the peat-like humus, must have formed a much-needed foundation on which to support the tangled forest of vegetation that grew and accumulated in all the quaking, boggy marshes. These creeping stems are called Stigmaria, and were known for a long time as one of the most abundant fossils of the coal, before their relation to Sigillaria was so much as suspected. They have markings arranged something as in Lepidodendron, but when we find them undisturbed—still imbedded by the old soil in which they grew—there arise from the center of the several scars long, thread-like filaments now known as rootlets (Fig. 7).

Almost every seam of coal has been shown to rest on a bed of clay, called among miners the under-clay or dirt-bed. This clay is penetrated in every direction by fossil roots with upright stumps sometimes attached, and it requires no argument to show that it is an old fossil forest bed—the original soil in which some, at least, of the coal-plants rooted and grew. This old soil has always been known to be particularly rich in Stigmariæ with the thread-like rootlets still in place, but it was not until Mr. Binney and others discovered Sigillarian stumps arising from wide-spreading Stigmarian roots that the real relations of the two forms of vegetation were perceived and acknowledged. It is always easy to do a thing after we have been shown how, and so nothing is more common now in all the coal measures, both of Europe and America, than to find the upright stumps and the subterranean stems still maintaining their original relative positions.

Such, in some particulars, were the Lepidodendrons and Sigillarias of the coal age. The two groups of plants differ widely in some respects, but they are connected by a complete series of intergrading forms, and in all essential points of structure a close relationship is indicated between them. It is, however, in their relationship with modern plants that they are principally interesting. In the moist woods of New England, and farther south along the summits of the Alleghany Mountains, there lingers a group of little plants, called Lycopods, ground-pines or club-mosses, that must be regarded as the nearest living relatives of Lepidodendron. The habit of growth is very much the same; the mode of fruiting is almost identical; the little spores are produced with the same extravagant copiousness, and, being resinous, are highly inflammable. Both plant and spores—but particularly the latter—will bear long-continued maceration in water without undergoing complete decay; and so it is, in a great many respects, that our little club-mosses—rarely attaining the dignity of a

PSM V18 D637 Coal ferns and restoration of a calamite.jpg
Fig. 10.—Restoration of a Calamite. Fig. 11.—Coal-Fern: Callipteris sullivanti. Fig. 12.—Coal-Fern: Alethopteris Massilonis.

foot in height—are very exact miniatures of the ancient Lepidodendrons (Fig. 8). You may then, if you please, call the Lepidodendrons and their allies gigantic club-mosses; and yet, if you do no more than that, you will fall a long way short of doing them full justice. For though in the mode of fruiting they are indeed club-mosses, and nothing else, yet, as regards other essential structural characters, they deserve a much higher rank. Taking a section of the stem of Sigillaria, for example, and studying the arrangement of the tissues—the pith, wood, bark, and vascular bundles—we find a plan of structure that characterizes only the very highest of modern plants (Fig. 9). Apply the microscope to thin slices, and the most intimate connection with the pines is suggested; indeed, if there were only time, it might be shown that the range of relationship of these old plants extends over a wide section of the vegetable kingdom, and is of such a nature as to set them very much above their dwarfed representatives of the present woods, the club-mosses. In addition to Lepidodendrons and Sigillarias, the forests of the coal age supported many a tall pine, particularly on the uplands, while groves of reed-like calamites (Fig. 10) fringed the swamps; and the whole surface, both of swamp and upland grove, was covered with a dense undergrowth of magnificent ferns (Figs. 11, 12, 13). But the pines were not the pines of our woods, for some of them, through their broad, frond-like leaves and other characters, were allied to ferns, while all of them showed morePSM V18 D638 Coal fern hymenophyllitis alatus.jpgFig. 13.—Coal-Fern: Hymenophyllitis alatis. or less decided taints of characters inherited from club-mosses, or rather the characters were inherited with club-mosses from a common ancestor. The calamites, too, were a curiously mixed-up group, and even the ferns showed a most reprehensible lack of allegiance to the fern type, since most of them united characters that do not belong to ferns at all, but are found now only separated in the palms on the one hand, and the highest flowering plants on the other. It is extremely difficult to present in few words any clear picture of the old Carboniferous forests. The stately club-mosses towering above all competitors—real monarchs of the wood—ornamented from root to crown with beautiful carvings in regular and delicate designs; the magnificent ferns whose exquisite outlines are still preserved in the roof shales of every coal-seam; the dense, dark jungles, tangled and impenetrable; the heavy, steaming, miasmatic atmosphere; the astonishing luxuriance of all the vegetation—these all are themes that claim the attention of every writer or speaker on this subject. But to my mind the prime interest centers in the composite nature of the vegetation, with all its wonderfully puzzling and intricate relationships. He must be dull, indeed, who can not see that in this significant mingling and blending of characters, the old coal forests epitomize and foreshadow all subsequent vegetation. All the structural elements were there; almost every fundamental type had a place in some of the curiously constructed plans of plant-life, and all progress in higher vegetable organization since then has come about through the unfolding and development of the possibilities, the carrying out of the promises, and the fulfillment of the prophecies that were woven into every tissue of the old ferns and club-mosses. The types that lay latent in the oldest vegetation have simply been separated and perfected; progressive development has been gradually led along a series of intricate but constantly diverging lines that lead out and up, and finally terminate in the endless graded ranks and profuse varieties which constitute the grand flora—the grandest the world has ever seen—that annually buds and blooms, and bears its wealth of leaf and fruit for you and me, provided only we appreciate it all. Indeed, the whole world, past and present, is ours, but only so far as mind and soul can lay bold of and possess its wondrous beauty, and still more wondrous meaning; beyond that it belongs to the dull ox as muck as to us.

But life has never been the exclusive property of plants, at least not since the geological record accessible to us began. Neither have plants monopolized the significant facts from which we may draw interesting conclusions regarding the laws of Nature and of being. In our study of the coal, we catch glimpses of animals that are worthy of notice. Their remains are left, along with the remains of plants, imbedded in the coal itself, or in the strata that limit the coal-seam above and below. Time will permit us to notice only a few examples. We must omit all description of the large, clear-winged insects that flitted in and out among the calamites and ferns, as well as of the curious spiders that laid snares for them in all available places; and we can only mention the scorpions and cockroaches that hid in the chinks and crevices of the fallen pines and club-mosses. All these would be interesting enough if time allowed, and interesting too would be the centipeds and land-snails that Dawson found in hollow Sigillarian stumps of the coal-measures of Nova Scotia. All would tend to enforce the lesson that the world in the Carboniferous age was controlled and operated very much as at present. Trees germinated and grew to perfection and died, and the hollow stumps became the refuge of myriads of creeping things, that found safety from hungry enemies only in complete concealment.

It is to the animals of higher rank that we must give attention. Let us remember that the Carboniferous age comes just after that which witnessed the introduction of fishes—the earliest as well as the lowest of animals having brains, and heads, and spinal columns. It lies, therefore, very near the focus toward which all the genealogical lines of our present vertebrates converge, and hence every structural feature in the higher Carboniferous animals becomes invested with a peculiar interest. Of true fishes there were none—they are a much later product—but, of creatures that combined in the most unthought-of ways the characters of both fish and reptile, the seas seem to have been full. Fishes of the gar-pike pattern (and yet not like that either, for they were of no one pattern in particular), with lungs far enough developed to enable them to carry on respiration in the air as well as in the water, were on the whole most abundant. In some particulars these creatures stood very low in the scale of fish-life, and yet in others they outranked any fishes with which we are familiar. The curious mixing of class characters produced results always interesting, though sometimes ludicrous. The incongruity of these combinations seems to culminate in that absurd creature, neither one thing nor the other, from the coal-fields of Bavaria, which had the head, gills, back-bone, and body generally, of a fish mounted on the limbs of a reptile (Fig. 14). Then there were real reptiles in the forests and coal-marshes; at least there were animals that by way of courtesy we may call reptiles, for they breathed air only, they were provided with true reptilian limbs, and the body was incased in a complete outfit of the

PSM V18 D640 Archegosaurus.jpg
Fig. 14.—Archegosaurus.

most approved reptilian armor. But in some respects they were not reptiles: the skeleton was imperfectly developed; the spinal column was such as belongs, of right, only to fishes; while the head and its articulation with the body, considered alone, would place them with the frog and salamander among the naked amphibians. These reptile-like creatures seem to have divided very early in their history, so as to follow two distinct lines of development: one group of small symmetrical forms, light of foot and swift of motion, frequented the higher portions of the land, and sought its food among the tribes of insects; the other, with strong limbs and jaws, with heavy body and aquatic habit, played the part of crocodiles. Now, these crocodiles were the lords of creation. All the while our coal was forming they stood at the head of created things. Had any human intelligence, with skill to read the geological record of all preceding time, been permitted to look in upon the Carboniferous world, he might well have believed that the end had come. He would have seen evidences of decay in many of the living tribes, and would have noticed that in all the past there were signs and promises and apparent preparations that seemed to point to these very tribes, and particularly to the crocodiles, as the complete realization and fulfillment of all creative designs. His human blindness to the future would have prevented his seeing any promise beyond. But prophetic indications always become plainer after their fulfillment, and so we, by the aid of all subsequent life-history, are able to read in the structure of the Carboniferous reptiles the promise of better things. As the age draws on to its close, certain characters become more and more pronounced in some of the old, half-formed crocodiles, while a totally different set of peculiarities come to the front in others. Taking the whole group together, we find a very wide range of affinities indicated. One of these points by unmistakable signs to the dinosaurs—great, biped, bird-like reptiles that became conspicuous in the age following the coal. From these the passage is direct to the reptilian birds of the same age, so like dinosaurs in many particulars that they can hardly be distinguished. Then follows, after delay and successive changes of form reaching over geologic periods, the real bird type of our woods and fields, marvelous in its perfect adaptations and marvelous in its perfect symmetry and beauty.

But some of those old reptiles are fraught with suggestions of still higher meaning. In some of the groups recently brought to light from strata that mark the closing epochs of the Carboniferous age, the coming mammal is very plainly indicated. And so, if we only read aright, we may find in our piece of coal the suggestion and the promise of even the highest forms of life.

So it is that we have a very direct interest in that old coal age, an interest altogether independent of the coal itself, even though we know that modern industry and commerce and civilization, and the great centers of human population—the manufacturing and commercial cities, with all their wealth and magnificence—are directly dependent upon its marvelous stores of energy. The physicist will tell us how that energy, which drives our engines, warms and lights our rooms and makes it possible for us to sit here in comfort and never miss the light of the sun to-night, is simply so much force derived from the sunbeams of the Carboniferous age, invested for our benefit in the old ferns and club-mosses; and yet our interest in the coal rises above all this. The roots of the present strike very deeply into the past, and nothing is risked in saying that, had the Carboniferous age, in its strangely constituted life-forms or in any other regard, been different in ever so small a degree, the present would not be just what it is. It is away back in the coal that we find, not only the promise of the grandly diversified system of vegetable life that lends so much of beauty and interest to the age in which we live; but it was then, also, that manifest preparations were made for bringing upon the scene the various specialized groups of animals that are to-day a matter of personal concern to every one of us. It was in the coal, too, that we found the first real evident but rude shapings of the organic frame which we ourselves wear. Hugh Miller—an authority that may be safely introduced on this occasion—was accustomed to quote approvingly from Drydon a stanza that to-day has more of meaning, perhaps, than either he or the poet ever perceived:

"From harmony, from heavenly harmony,

 This universal frame began;
From harmony to harmony,
 Through all the compass of the notes it ran,

 The diapason closing full in man."

All investigation only adds grander significance to the grand utterance of Agassiz, that "man is the end toward which all the animal creation has tended since the first appearance of the first palæozoic fishes."

Is it not true that "an increasing purpose" does run through the ages by the processes of which, not only "the thoughts of men are widened," but enlarged encouragement is given to all their hopes and expectations of the future?

 
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