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,) gray and bluish clay slate, hard bluish sandstone, shale, or, as they term it, shiver, white micaceous sandstone, extremely hard; blue slate and shale intermixed, black slate, and then the coal. The depth of these strata differed so much in different pits, that their individual thickness could not be ascertained. Vegetable impressions are very common in the slate next the coal; and they have found the impression of a fish. Pieces of pure charcoal, in the form of sticks, or logs, are frequently found in or on the coal. In sinking one of the pits they met with a perpendicular column, 8 inches in diameter, extending through the slate into the coal; in all about 50 feet. Its surface was distinctly serrated, and at intervals of about 2 inches it appeared jointed, breaking easily at the joints. For the want of a better name I must call it a "lusus naturæ;" for it is neither clay-slate nor mica-slate, nor shale, nor sandstone; but appears to be composed of them all. Masses of a black oxide of iron are sometimes found in the slate; and from its weight and hardness the miners very properly call it ironstone. Iron pyrites are very abundant in the slate, and the heaps of rubbish are white with the sulphate of alumine; yellow ochre is found among the rubbish, but I could not ascertain its relative position with any precision. The side of the hill at the pits is covered with quartz pebbles; some of which are as transparent and beautiful as I ever saw. The country, for several miles around the pits, (i. e. as far as I have seen,) appears to be entirely destitute of rocks or pebbles, and is covered with a light sandy soil. I am unable to inform you of the number of hands employed at, or of the quantity of coal annually furnished from, these pits, as a part of my notes has, by an accident, been rendered illegible.
Thus, sir, I have endeavoured to comply with my promise of giving you an account of the coal pits.[17] In doing this, I have only attempted to state facts as they existed; although I have no doubt that my imperfect acquaintance with geology has occasioned many omissions which might have been interesting. To the same cause must be attributed the use of language not always strictly scientific, and a method less exact than might have been desired. With all its imperfections, however, if you can, from the mass of facts, cull any one which may be useful or interesting, I shall be fully compensated by the pleasure of having furnished it, for any trouble I may have been at in doing so. And, if at any time I should be able to furnish you with any information relative to the mineralogy or geology of this part of the country, I hope you will let me know it.
Art. IV. Sketch of the Geology and Mineralogy of a part of the State of Indiana.
Art. IV. Sketch of the Geology and Mineralogy of a part of the State of Indiana, communicated in a letter to the Editor, by Mr. W. B. Stilson.
Louisville, (Ken.) August 11, 1818.
Dear Sir,
I have employed a short period of leisure in passing over a portion of the state of Indiana. Among other objects, I was not wholly inattentive to the mineralogical and geological features of the country. I now, with diffidence, transmit to you the result of my inquiries.
Sketch, &c.