39 



erally rather soft. In rare cases it is so hard that it emits 

 sparks when struck with a hammer, but usually it soon slakes 

 down into an incoherent mass upon exposure to the air. Where 

 the horseback enters the top of the coal seam the fissure at once 

 becomes wider. The upper laminae of the coal, immediately 

 adjacent to the fissure on the overhanging side, are more or 

 less steeply bent downward, the bending or buckling of the 

 layers fading out laterally within a few feet from the fissures. 

 Fragments of the black shale, from the roof of the coal, were 

 seen at many points in the clay filling of the horsebacks from 

 five to twenty-nine inches below the top of the coal. In mine 

 number 5 of the Springfield Coal Mining Company, a fragment 

 qf coal, six inches long and three fourths of an inch in thick- 

 ness, was found in the clay of a horseback nine inches below 

 the bottom of the coal seam. 



In the mine last mentioned there was seen in three of the 

 horsebacks a slight upward bending of the lower edge of the 

 coal on the side of the fissure opposite to that in which the 

 down-bending at the top occurred. This upw^ard bending at 

 the bottom, however, is only one third to one half as great as 

 the down-bending of the coal at the top of the seam in the 

 same horseback. When the clay seam passes into the coajl bed 

 in a nearly vertical direction there is a down-bending of the 

 coal at the top of the seam on each side of the fissure. How- 

 ever, the more nearly vertical the direction in which the horse- 

 back cuts through the coal, the less is the distance through 

 which the edges at the top and bottom of the seam are bent. 



In no instance was there seen a true faulting of the beds. 

 I wish to emphasize the fact that in no case was there a slipping 

 of the middle part of the coal seam on one side of the fissure 

 above the level of the corresponding part of the seam on the 

 opposite side. The only vertical displacement is a downward 

 pushing of the cap rock and roof shale, and a down-bending of 

 the upper laminae of the coal on the overhanging side of the 

 fissure, through a vertical distance of from two to twenty 

 inches; and, less frequently, a much smaller upward bending of 



