Art. III. Account of the Coal Mines in the vicinity of Richmond, Virginia.
Art. III. Account of the Coal Mines in the vicinity of Richmond, Virginia, communicated to the editor in a letter from Mr. John Grammer, Jun.
Petersburgh, Virg. Jan. 28th, 1818.
Dear Sir,
In compliance with your request, that I would send you some account of the Virginia coal pits, I paid a visit to them soon after my return, in company with Mr. R. W. Withers, and I will now proceed to give you the account proposed.
The pits, which we made the particular object of our visit, are situated in the county of Chesterfield, about 14 miles distant, in a direction W. S. W. from Richmond, and 3 miles south of James' River. The country rises gradually from Richmond to the pits; and, from its sandy appearance, is evidently an alluvial deposit, although its substratum is the granite mentioned by Mr. M'Clure, as extending through this state from S. S. W. to N. N. E. The coal is found on the western or upper surface of the granite, coincident with it both in direction and inclination; but whether they come immediately in contact or not, has not yet been ascertained. The 'bed' of coal is supposed by the miners to be coextensive with the granite, and I can discover no very good reason for disagreeing with them in this particular; but, on the contrary, many circumstances concur to strengthen the opinion that it is really coextensive with the granite. The coal is now procured from at least 25 different pits, opened at convenient distances through an extent of from 50 to 70 miles. It every where commences at the upper surface or termination of the body of granite. Some suppose that it is imposed on the granite; and others, that a thin stratum of slate is interposed between the coal and granite. It is always found covered by the slate. The granite is inclined to the horizon at an angle of 45°, and the coal has the same inclination. And since the coal, as far as it has been discovered, is found to accompany and correspond with the granite, why may we not suppose that it continues to accompany the granite, where it has not yet been discovered? At Heth's pits, the coal is 50 feet thick, measured on a line perpendicular to the surfaces of the extreme strata. At some of the pits between Heth's and James' River, it is 30 feet thick; and at the river, not more than 25 feet. The thickness of the coal on the north side of James' River, at the pits in Henrico and Hanover counties, is variable, but at no place greater than 25 feet; and to the south of Heth's, in the pits extending to the Appomatox river, it is still less thick. These facts would induce the supposition, that the coal was deposited in a bed, near the centre of which Heth's pits were sunk. But, on the other hand, the coal is distinctly stratified, and the number of strata increases as the coal proceeds from the surface of the earth; of course, therefore, the farther you proceed from the outer extremity of the coal, the thicker the body of it will be found; and from the inclination of the coal, the farther you are from its outer extremity the deeper it must be under the surface of the earth. Heth's pits are 100 feet deeper than any that have yet been sunk; and all the pits, that I have seen, appear to be nearer to the outer extremity of the coal. We may conclude, therefore, that if the others had been sunk as far from the outer extremity, they would have been as deep, and the coal would have been found as thick in them as in Heth's. Heth's pits, now so called, were first opened about 30 years since, and worked to some considerable extent. Experiencing, however, much inconvenience from the near approach of the works to a part of the coal which was on fire; and finding, from their unskilful mode of mining, that the business was not profitable, they abandoned the works, and filled up their shaft. Some few years after, Mr. Heth obtained possession of the land; and, having imported two Scotch miners, commenced working the coal again. He has now three shafts open, in a line with each other, in the direction of the vein. They are sunk near the brink of a steep hill, which rises about 180 feet from the western bank of a small brook. The depth of one of the shafts is 350 feet. The other two are about 300 feet deep, each. A steam-engine, constructed by Bolton & Watt, is erected at the middle and deepest shaft. It is used exclusively for pumping out water; but I will not trouble you with an account of the modus operandi, as it would be only a repetition of your own description of the same operation at the Cornwall mines. The coal is raised in a box, called by the miners a cowe. These cowes contain about two bushels each, and two of them are alternately rising and descending in each shaft. They are raised by means of ropes, fastened to a simple wheel and crank, which is turned by mules. In sinking their shafts, they cut, in the first place, perpendicularly (i. e. to the surface of the earth) through the coal, to its lower surface; and then turning westwardly, they open a horizontal gallery through the inclination of the vein, to its upper surface; by this means, to use their own terms, "gaining a double cut on it." Their principal gallery passes (in the direction of the vein,) by the mouth of each shaft. Its length is 1350 feet, and it is terminated at each end by a hitch or dyke of hard sandstone. (The passage was stopped with rubbish in such a manner as to prevent me from seeing the stone myself, and the gentleman who escorted me through the mines is my authority for its being sandstone; he might possibly, however, have been mistaken, as it is difficult to ascertain what a stone is, in such a place, until it is broken.) When I was at the pits, they were preparing to blast through this rock. At right angles to the principal gallery, they have opened, at convenient distances apart, shorter galleries, running westwardly, and these are again connected by passages parallel to the first or principal gallery. Pickaxes are the only tools used in working the coal, as it breaks very readily, in the direction of the strata. The roofs of some of the passages are perfectly smooth; and in such, the light of the lamps, reflected from the great variety of colours in the coal, presents a very brilliant sight. The gloomy blackness, however, of most of the galleries, and the strange dress and appearance of the 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,) 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.