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