rocky rind of the earth. Above us, the mouth of the shaft seems narrowed by perspective into an insignificant hole; before us opens a dark street, over which, on a tramway, mules are hauling car-loads of coal, which is starting on its journey to the populous city (Fig. 61). Miners, with their picks, are moving to and fro; the sound of hammers is heard; the paraphernalia of busy life are about us, and we seem translated to a nether world. We feel like the hero of the Latin song, who got permission to visit the realm. of Pluto, and make the acquaintance of unborn spirits destined to dawn upon the world in the coming Golden Age. Where is the Styx and its sleepy boatman? Where are the shades that expectation thinks to see flitting before us? Let us enter this dingy street, and conjure spirits from their Lethean sleep upon the coaly couches that line the passage-way.

The seam of coal is a broad, horizontal sheet or bed from three to five feet thick. In this are excavated passages about eight feet wide and about five feet high. A main "gangway" may be half a mile or a mile in length. From this, at suitable intervals, lateral passages or "chambers" are quarried out, running nearly at right angles with the main gangway. The same bed of coal may be pierced by several gangways-diverging from each other as the ave nues diverge from the Capitol at Washington-from each of which extend numerous lateral chambers. These chambers often intersect each other, and thus constitute a network of passages like the streets of a city. Along the principal passages tramrails are laid for the transportation of the coal in trams, or little cars, from the remote portions of the mine to the shaft. Each miner employs a separate tram, and receives a stipulated amount per ton for the coal sent up by him. The trams are moved over the track by mules, which often spend their lives under ground. They

Fig. 62. Explosion in a Coal Mine.

are stalled and fed in side-rooms excavated in the coal and superincumbent rocks. The requisite circulation of pure air is maintained through the mine by the consumption of refuse coal at some suitable place, the smoke and heated air from which ascend through a separate shaft. The escape of heated air through this shaft causes a descent of external air to take place through the main shaft. Communication between the two shafts is effected only through the remote portions of the mine, so that the pure air is made to permeate all the passages. Still there must always be side-rooms through which no circulation can be effected, and here not unfrequently collects that explosive fire-damp," or light carbide of hydrogen, so often evolved spontaneously from the coal, and so often the cause of fatal accidents to the miners (Fig. 62). When the seam of coal is less than five feet thick, it becomes necessary to remove some of the superincumbent rock, to render the roofs of the main passages sufficiently high for the mules to travel under them.

Thus entire square miles of a coal-seam, hundreds of feet. beneath the surface, are perforated in all directions by the hand of the miner (Fig. 63), as ship-timber is riddled by the depredations of the Teredo.

By the feeble light of our miner's lamp we enter one of these dusky aisles. The substratum beneath our feet has been ground to dust. The whole thickness of the coalseam is exposed along the lateral walls. Occasionally it presents gentle undulations instead of lying in a rigidly plane position, and not unfrequently a huge bulge of the underlying rocks completely cuts off the seam. Overhead a black, bituminous shale forms the ceiling. Perhaps here and there the white shell of a univalve or a bivalve projects from the surface-the products of the sea buried in their native sediments, and suspended above our heads.

G

What a change in the condition of things since those little animals lived in the shallow surface-waters in which those sediments accumulated! Lo! here above us is a mirrorsurface gleaming in the light reflected from our lamps. Its polish is like that of jet, and yet it is wrought upon the face of the solid rock. Some slight movement of the

Fig. 63. Miner at Work-old manner of working.

earth's crust has cracked the shaly roof; the opposite sides of the fissure have been moved to and fro over each other, and under the mighty pressure the two opposing faces have been beautifully polished.

But probably different sights will greet our eyes. The rocky ceiling is ornamented every where by the most exquisite tracery-inimitable representations of the delicate fronds of ferns (Fig. 64). We remove a scale of the rock, and behind is still another picture. Remove a second, and from the dark black rock gleams forth another form of grace and beauty. The whole mass of the shaly roof is a portfolio of inimitable sketches. The sharpest outlines and minutest serratures of the leaves are clearly traced. The very nerves, with their characteristic bifurcations, are accurately depicted on this wonderful lithograph. Petioles, and buds, and woody stems, and

Fig. 64. Coal Ferns.

cones, and fruits, slender grass-leaves, striated rushes, the