mosses do not exceed three feet in height. The stems of Lepidodendron, after the falling of the leaves, were covered with scars diagonally arranged, and are often mistaken by the uninformed for "petrified snakes." The cones of these plants are found in great abundance in Ohio. Another curious form of this period has been styled Sigillaria. Their fluted trunks, from one to five feet in diameter, have sometimes been seen sixty and seventy feet in length. The flutings are marked by a longitudinal series of pits, like the impressions of a seal. In many instances these tree-trunks have been found erect, evidently buried while standing by accumulations of sand and mud (Fig. 67). Below are the roots and rootlets-formerly called Stigmaria-and the very soil remaining in which they flourished. In the excavation of a bed of coal these petrified tree-trunks are not unfrequently cut off below, when the slight taper of the stem permits them to slide, by the force of gravity, down into the mine. These "coal-pipes" are much dreaded by the English miners, for almost every year they are the cause of fatal accidents. "It is strange to reflect," says Sir Charles Lyell, "how many thousands of these trees fell originally in their native forests, in obedience to the law of gravity, and how the few which continue to stand erect, obeying, after myriads of ages, the same force, are cast down to immolate their human victims."

Let the reader embody before his mind's eye a group of rush-like and fern-like trees and under-shrubs, interspersed among gigantic club-mosses and occasional conifers, and he has a picture of a carboniferous jungle-a jungle not enlivened by the tread of quadrupeds or the singing of birds, but mute as the solitudes of an African desert-voiceless save when the alligator-like bellowings of the Archegosaurus in a neighboring bayou waked the echoes of those gloomy corridors, and startled the lesser amphibia from

Fig. 67. Trunks of Sigillaria in the Mine of Treuil, at Saint Etienne.

their hiding-places, or the thunder-voice of Deity spoke, ast it still speaks, from the terror-striking tempest.

The office of this redundant vegetation was finally fulfilled. The atmosphere was purified of its noxious elements, and higher creatures could live upon the soil. Behold the wisdom and providence of the creative Architect! Carbonic acid was to be removed from the atmosphere, to fit it for animal respiration. A finite mind might have aimed to effect this end alone. Omnipotence was competent to annihilate the poison, or convert it to some solid or liquid form. The infinite Intelligence, however, had so planned the universe that the poison of the quadruped was the food of the plant. The very execution of one portion of the cosmical plan created a use for that which impeded the execution of another. A double object was thus effected. Nor was this all. Should these enormous crops of vegetation grow up and pass away unutilized for the want of an intelligent population to consume and use the fuel? It was not so to be. Though man was not except in the conceptions of the Almighty, man was regarded in the preparations of this age. The far-seeing Planner of the universe stored the carboniferous fuel in repositories where it could never perish, and where it could await the uses of the coming race of man. Nor was this even the end of the providential purposes. In a subsequent age those barren rocks and those beds of coal became covered, first with the basis of a soil, and then with the soil itself; so that man, when he should come upon the stage, might find an inexhaustible mine of fuel, and a foothold for the products of his farm, upon the self-same acres. Another circumstance should also be here remarked. The preser

vation of these carboniferous stores was effected by the packing down of layer after layer, while beds of clay, and sand, and calcareous sediment were interposed between

them. Not only was there never another period of the world when the supply of carbon was so great, but never, before or after, were those frequent and gentle oscillations so long continued which were the agencies in burying the successive crops of vegetable growths. At least, such frequent oscillations never before or since occurred at a time when the level of the continents so nearly coincided with the level of the sea. And, lastly, these very oscillations, while they were subserving this collateral end-which was still important enough to have been the sole and ultimate end-were only the symptoms of a great continental preparation, which was going on from the region of the Atlantic to that of the Pacific shores, and which had been in progress, and attended by similar, though much less frequent oscillations, from that remote period when the shrinking of the molten nucleus of the world located those huge wrinkles in the stiffening crust which were to be afterward deepened into the beds of the two great oceans. Verily, here is a scope and comprehensiveness of plan which must command our highest admiration.

The same general preparatory movements were still to be continued-continued till the finished earth had been elaborated for the reception of man. It would seem that the frequent oscillations of the Coal Period were but the tremblings of the strained crust, pushed to the very verge of violent rupture by the two enormous masses of water. By turns, the central areas had been protruded above the waves, and by turns the tension had found relief, and the uplifted crust dropped back for a time to its submarine horizon. Not before the collateral uses of these phenomena had been subserved did the tension of the crust reach the measure of a grand upheaval. After trembling for ages beneath the immense and increasing pressures of two great oceans, it burst up in enormous folds thousands of

feet in height, and extending from New England to Alabama. Some of the folds of the Appalachian upheaval, according to the grand generalizations of the brothers Rogers, were protruded with so abrupt a flexure, and to such a dizzy height, that they toppled over toward the west; while to the west of the principal axis of violence the folds become gentler, and terminate in pleasant undulations of the surface. The Queen City of the West stands, perhaps, on the last of this series of undulations. Thus were the Appalachians brought into existence. Thus were the deep-seated beds of coal lifted above the general level of the land, and brought within the reach of moderate excavations, accompanied by the requisite conditions for natural drainage of the mines (Fig. 68).

Fig. 68. The North American Continent at the end of Paleozoic Time, or beginning of Mesozoic. (The dotted lines represent its present outlines; the broken lines the rivers.)