COAL-MINES AT ROCK ISLAND.
"The coal of Rock Island and vicinity forms a part of the northern border of the great Illinois coal-field. The lower Carboniferous rocks here come to the surface, resting upon Devonian or Silurian strata. Deeply cut by the great valleys of the Mississippi and its tributaries, and removed by extensive denudation, the coal formation exists as a series of outliers, occupying the highest points of land. In all the deep valleys it has been swept away, and its ruins have gone southward to form the rich alluvials of the Lower Mississippi and the deltas at its mouth.
"The coal is found associated with sandstones and limestones in thin bands between heavy beds of shale. One workable seam only has been found, which has an average thickness of about three feet six inches. It is, however, quite irregular, being liable to very sudden contractions and expansions. The coal lies high above the streams, and is very favorably located for mining. It is generally reached by drifting into the hill-sides. The roof is limestone or calcareous sandstone, occasionally separated from the coal by a thin band of shale. Beneath lies a very bituminous shale, sometimes graduating into an inferior coal, and resting upon a bed of fire clay. This shale abounds in fossil plants, often in a very fine state of preservation, prominent among which are huge reeds and ferns, mingled with plants of great delicacy and beauty. The fire-clay has been tested and found valuable. It is extensively used by Thomas & Joury, at Car bon Hill, in the manufacture of pottery, fire-brick, and tile.
"Most of the mines of this district are small, averaging from ten to thirty tons daily yield. The mining is done at the outcrop on the hill sides, and the coal is generally carted to Rock Island by teams. The mines are from eight to ten miles distant from the river; and this long transporta tion is a very serious drawback upon the profits. The only large mines are those of Cool Valley, owned by S. L. Cable, Esq., of Rock Island. This is one of the best-organized mines in the country. Mr. Cable has built a railroad, twelve miles long, from Rock Island to his mines, over which his coal is carried to market. His annual product is about 60,000 tons, which is marketed mainly at the river and carried westward into Iowa. It is extensively used by steamers, and supplies the large towns of Eastern Iowa with fuel and gas. About 80 hands are employed, most of whom are common laborers who have taken up mining and acquired their skill by practice in these mines. They work under an arrangement as novel as it is successful. The miners and the owners of the mines are parties to a mutual understanding, by which the railroad receives one-third, the mine-owner another, and the operatives one-third of the price per ton which the coal brings at Rock Island. This arrangement works admirably.
It secures the best class of labor, avoids strikes, encourages men to establish permanent homes, and secures the steady development of the mines. It is eminently profitable to all parties. It is intrinsically just and humane, and has the additional advantage of putting more money into the pockets of mine-owners and operatives than the old method.
"The mine is opened in the side of a steep bluff south of Rock River. The coal is brought to the cars, which run to the mouth of the drift, by mules, over a wooden track. The seam is here about four feet thick, with excellent roof and floor, but is subject to some slips and interruptions. In running the main entry back into the bluff; at a distance of about 60 rods from the opening, the coal suddenly gave out, and was replaced by a mass of sand and gravel, mingled with large stones and drift-wood. This occurrence puzzled the miners considerably, and was supposed by some to be a fault or slip of the strata. On examination, however, of the sur rounding country, the real nature of the interruption becomes obvious. The coal and its associate rocks come in again, and are seen in their proper place, though a large extent of the formation is gone. It has been cut out by denuding agencies, similar to those which are now at work in every valley where water flows. But the space has filled up with material washed in by powerful currents while the surface suffered a temporary submergence. The phenomena probably belong to the drift epoch, when extensive areas of the earth, which had been above water for ages, sub sided below the ocean and became covered with the deposits of clay, gravel, and boulders which form the surface so generally in the North temperate zone. (?) Possibly it is altered drift, washed in by the Mississippi at its flood when its waters flowed hundreds of feet above their present level. Fresh water has certainly stood on the highest lands of this region; for on the hill-tops deposits of loamy clay are everywhere visible, containing fresh water shells. All shallow beds of coal are liable to these interruptions. In regions which have been subjected to extensive inundation, cutting broad and deep valleys, and especially where the deposit of drift is thick, the greatest care is required in opening mines where a heavy outlay is to be made. A thorough survey by a competent geologist is an essential prerequisite to any large investment in improvements.