the appearance presented by the "upthrows and downthrows," the "faults and dykes" of many coal-fields, and especially of those of the Scottish Lowlands.

Composed, like other systems, partly of stratified sediments, and partly of unstratified masses which were the volcanic products of the period, the Coal-measures present no great difficulty as a Rock-Formation, and few of its strata have undergone much metamorphism or internal change, unless where in contact with igneous eruptions. In its stratified rocks we perceive the obvious sediments of seas, lagoons, and estuaries, the relics of shell-beds and coralreefs, the vegetable growths that accumulated for centuries in swampy morasses,* flourished in the virgin forests, or tangled rankly in the river-jungle; and in its unstratified, the eruptive mass, the molten overthrow, and the frequent shower of dust and ashes. Interrogated as mere rockmasses, they expand overflow after overflow, and stratum upon stratum, like the leaves of a mighty volume, and tell of gigantic rivers and estuaries, of shallow seas, tides, and ocean-currents, of low-lying continents and volcanic archipelagoes, of shell-beds and coral-reefs, of vegetable growth and vegetable drift, of rains that fell, winds that blew, and suns that shone and gladdened the face of nature even as they do now. Of all this, and much more, these coals and sediments bear abundant testimony; and interesting as it must ever be to the educated mind to trace back the unity and continuity of the physical agencies that mould and mo

* A curious proof of the morass or swamp-growth of many of our coal-seams is to be found in the narrow winding "wash-outs" by which they are frequently intersected. These "wash-outs" of the miner are stream-like courses from which the coaly matter has disappeared, its place being taken by stony substances. They have been clearly runnels or watercourses that threaded their way through the swamps, and thereby prevented the accumulation of the vegetable matter, just as at the present day our peat-mosses are cut into channels by the streams that may drain their surfaces.

dify the face of nature, that interest becomes immeasurably enhanced when we associate the results of these old-world operations with the necessities of the present, and trace in them an obvious provision for the social and intellectual advancement of man.

We come next to consider the Carboniferous system as a life-period, and though there must necessarily be considerable differences between the fossils of its respective divisions carboniferous shales, mountain limestone, and coalmeasures—yet in a sketch of this kind the aim is more an outline of the whole than the consideration of specific minutiæ, which can only be appreciated by the professed palæontologist. Perhaps the most remarkable feature of the period is its Flora-a flora remarkable not only for its vast exuberance, but for the peculiar character of its plant-forms, which bear, in most instances, but a faint resemblance to those of the present day. This vegetation is for the most part converted into coal, but here and there, scattered throughout the shales and sandstones, we find leaves, fruits, stems, trunks, and roots, which indicate its nature, and from these the botanist must construct the aspects of the carboniferous flora. Sea-weeds, marsh-plants like the equisetums, reeds, and rushes, a vast variety and exuberance of gigantic ferns and clubmosses, pine-like trees with their leaves and cones, and a still greater number perhaps which cannot be assigned to any existing order, may be said to constitute the bulk of the coal vegetation. Fragmentary, and converted into coaly or stony matter, the botanist has no easy task in reading these old-world forms, and all that he can in many instances do is to trace a resemblance and give a name founded on some external peculiarity. It is for this reason that we find in lists of carboniferous plants such names as calamites (reed-like), equisetites (equisetum

like), lycopodites (clubmoss-like), sphenopteris (wedge-leaf fern), neuropteris (nerve-leaf fern), lepidodendron (scalybark tree), bothrodendron (pitted tree), and so forth, all pointing to some obvious feature which distinguishes them one from another, but throwing very little or any light on their true botanical affinities. But whatever their strict affinities, we know that most of them belonged to the lower orders of vegetation-the horsetails, ferns, and clubmosses, the grasses, sedges, and rushes, the cycads and pine-trees, or perhaps more properly to extinct forms that stood intermediate, as it were, between these various orders. Though lowly in organisation-and most of them were undoubtedly so-they seem to have occupied large areas of the earth for ages, and to have grown in rank luxuriance, till in numerous instances their accumulated masses form seams of coal from a few inches to many feet in thickness.

When we turn to the Fauna of the period, we find throughout the same variety and the same numerical abundance, though, of course, certain forms are more abundant in one portion of the system than in another. These forms, too, are chiefly aquatic-fresh-water, estuarine, and marine; there being few terrestrial species yet discovered, and these only at wide intervals and in few localities. Beginning with the lower forms, we have a number of minute foraminiferal organisms, and a vast exuberance of corals and encrinites, so vast that beds of the mountain limestone, hundreds of feet in thickness, are almost entirely made up of their remains. There are also trails, burrows, and tubes, that indicate the existence of marine annelids; abundance of crustaceans, some minute and bivalved like the cypris, a few species of trilobites, and others like the king-crab, and of large dimensions. The polyzoa or flustra-like organisms occur too in great variety, scattering their netted cells through the shales and limestones; and shell-fish of every

known order- bivalve and univalve, deep-sea and shore dweller occur throughout the entire system, though most abundantly, of course, in the marine beds of the mountain limestone. Fishes of many forms are likewise abundant, especially in the lower series of the system, their shining enamelled scales, predaceous teeth, and defensive fin-spines being scattered through the shales, ironstones, and limestones. Many were large and shark-like, their palatal teeth, jaws, scales, and fin-spines indicating lengths from twelve to eighteen and twenty feet, and bulky in proportion. Being chiefly cartilaginous, their bodies have in most instances utterly disappeared, and only their teeth or enamelled finspines remain to testify to their existence. We have seen hundreds of teeth and spines from a single layer of blackband ironstone, and yet no other vestige of the fishes to which they belonged, not even a patch of scales in juxtaposition, to indicate their affinities. Higher than fishes, reptiles also make their decided appearance, most of them aquatic and fish-like in form, though a few ascend to true lacertilian or terrestrial species. Of the terrestrial fauna of the period we know little; but the insects, land-snails, and reptiles of arboreal habits, which have been found in certain coal-fields, were surely not the sole inhabitants of the carboniferous islands and continents, and we may safely look forward to the discovery of other and higher forms of which these were the necessary congeners. Even while we write, the announcement of several new genera of reptiles from the coal-fields of Northumberland and Lanarkshire gives additional encouragement to this expectation, and all that seems necessary to its fulfilment is merely more minute research and more careful examination on the part of palæontologists. Indeed, when we consider the difficulty of preserving terrestrial organisms, how much they are subjected to waste and decay, and how few are necessarily

washed down into estuaries and seas of deposit, it is wonderful to learn that such fragile remains as those of insects, land-shells, and tree-reptiles should have been saved from destruction. And surely, if larger and stronger terrestrial forms had existed, the hope may be indulged that they too have been preserved, and will one day or other be detected.

Such is a hurried glance at the Life of the old Carboniferous period, and more especially as displayed in the areas of Europe and North America, where mining operations have been most extensively conducted. Whether these extensive coal-fields were all contemporaneous is a subject open to question. Indeed the probability is that they were not strictly contemporaneous, but merely belonged to a great cycle of the earth's history characterised by these coalforming conditions, and in the main by the same facies of plants and animals. But however this may be decided by future and more exact inquiry, we perceive in the mean time a wonderful similarity all over the old coal-measures, and an exuberance of life that has never been excelled during any subsequent epoch. To account for this exuberance, especially in the vegetable world, various hypotheses have been advanced, such as a greater proportion of carbonic acid in the atmosphere, the greater amount of heat derived in those earlier times from the interior of the globe, a general lowering of the land-surfaces, and a higher temperature over the coal-yielding areas arising from some change (inclination of the earth's axis or otherwise) in the astronomical relations of our planet. In the present state of our knowledge and belief in the stability of the earth's planetary relationships such hypotheses are inadmissible, and we are driven to seek for the solution in the then distribution of sea and land, the climate thereby produced, the nature of the vegetation, of which we as yet know too little, and the