black miners, would furnish sufficient data to the conception of a poet, for a description of Pluto's kingdom. A strong sulphurous acid ran down the walls of many of the galleries; and I observed one of the drains was filled with a yellowish gelatinous substance, which I ascertained, on a subsequent examination, was a yellow, or rather a reddish, oxide of iron, mechanically suspended in water. I mentioned above that a part of the coal was on fire: I could not ascertain when this fact was first observed to exist; and it is not impossible that the coal may have been burning a century, or more. It is highly probable, however, that a comparatively small quantity of the coal is consumed, as the combustion must be greatly retarded by the absence of a sufficient portion of atmospheric air. A strong sulphurous fume issues from an irregular hole in the side of the hill of about 2 feet diameter. The hole appears to be only 4 or 5 feet deep, and the smoke rises into it from cracks, partly filled with loose clay. The earth is very much cracked around the hole, to the distance of 12 or 15 feet; and these cracks are from 1 to 4 inches wide. The mouth of the hole is encrusted with acicular crystals of pure sulphur. Attempts were formerly made to extinguish the fire, by turning water into this hole; and, after every attempt, there was a temporary disappearance of the smoke for several weeks; but never longer than three months. For several years, however, they have desisted from such vain attempts, and have taken advantage of the facility afforded, by the existence of this fire, for ventilating the mines, in the following manner:--They opened a passage from their present, to the old deserted, works; this they can open or shut, by means of a close door. As the old works are very near the fire, the air in them becomes very much rarified by the heat; and probably a considerable portion of it is consumed (as the principal pabulum for the combustion,) and a partial vacuum is produced. When the air in their present works, therefore, becomes impure, they open the door, and a strong current rushes into the old works; its place is again supplied with fresh air through the shafts. Previous to the adoption of this mode of ventilation, they experienced great inconvenience from carbonic acid gas; and some of the workmen had been killed by an explosion of carburetted hydrogen gas. Since this mode has been adopted, they have experienced no inconvenience at all from noxious gases. On inquiry, I was told that the substances passed through, in getting to the coal, varied in the different pits. As far, however, as I could learn by inquiry, and an examination of the heaps of rubbish, the following substances, in the order in which they stand, have been found in Heth's pits:--mould, clay, gravel, fuller's earth, sandstone, (at first extremely coarse and friable, but becoming more compact and hard, and having an appearance somewhat stratified as they descended,)