STEVENSON, COAL BASIN OF DECAZEVILLE, FRANCE 267 



The coal in the newer portion is 120 meters below the hilltop, and the 

 whole of this cover must be removed. The work of removal is done in 

 benches, each four meters high, and the coal occupies the first eight, 

 midway in the excavation. The disturbance in the coal is such that a 

 definite section cannot be obtained such as that at Tramont; it is impos- 

 sible to determine even the original thicloiess of the bed. But the fine 

 exposure on the easterly wall enables one to ascertain the general struc- 

 ture of the bed, while that on the southerly wall exhibits in part the 

 fold. Serious faults are distinct, but the mass of coal reaching to the 

 eighth bench is outside of the main fault and is continuous. 



On the eighth and seventh benches, there are eight meters of coal with 

 indefinite partings; whether or not these were persistent in any case 

 cannot be determined, because the coal is crushed by petty faults and 

 irregular folds. A clay parting three inches thick was seen on the sixth 

 bench and was followed for some distance, but it disappears abruptly, 

 as if cut off by a fault. Ironstone concretions are numerous on this 

 bench, and the coal has concentric structure around them. Some part- 

 ings and pockets of shale were seen on the fifth bench, but they are not 

 in their original position and their relations cannot be determined. A 

 three-inch bed of clay is shown on the fourth bench, where also are 

 numerous thin clay partings ; but most of them have been broken up into 

 small pieces with polished surface. A large mass of ironstone is a nota- 

 ble feature at this exposure. Throughout, the coal has been broken into 

 wedges, large and small, some of the former showing a lens-shaped sec- 

 tion. On the third is a streak of hard clay, six inches to one foot thick, 

 evidently persistent, for it crosses a fold on the main floor of the excava- 

 tion. The coal on this bench, as on those below, is much curled, and 

 faults of two to three feet are numerous. 



Here is a face, more than 100 feet high, and containing no certainly 

 persistent parting more than a few inches thick; indeed, to all intents, 

 the mass is continuous coal. Dips of 25 to 40 degrees were observed; 

 one may take 25 degrees as the average without danger of underesti- 

 mating the mass; the thickness of the bed may be about 90 feet. 



But underl3dng this coal is an argillaceous shale with some sandstone, 

 the top of which is seen in the lowest part of the decouverte. It is a 

 striking feature in the southerly wall, where its light color makes clear 

 the vagaries of the fold. When first encountered in the northerly part 

 of the excavation, this mass was 22 meters thick ; but it decreased rapidly, 

 so that in the bottom of the decouverte it is only six meters, while in 

 the Bourran shaft, 200 meters away, it has disappeared. Below it is 

 coal, more than six meters thick, which is not removed in the open work- 



