STRUCTURE OF RUBY HILL. 



31 



slightly yellow. Much of this clay is derived from the shale by attrition 

 and the decomposing action of waters passing along the fissure. 



Main fissure in the Richmond. — The fissure leaves the shale at a short cross-cut 

 in the Richmond ground just after the compromise line is passed, and is here 

 very narrow, although it is plainly defined, and contains from a few inches 

 to a foot of clay. It continues its normal course, and is distinctly visible, 

 with its filling of clay, along the northwest drift in the southeastern portion 

 of the Richmond seventh level. After leaving the shale the space between 

 the latter and the fault is occupied by stratified limestone, while the rock 

 lying on the southwest of it consists of the usual broken and highly meta- 

 morphosed limestone. On the surface this fissure can be seen near the 

 Richmond office. On the first level of this mine it is in contact with the 

 shale, 94 feet west of the Richmond shaft. On the second level it is 

 35 feet west of the shaft, and is also in contact with the shale, and re- 

 mains so down to the fourth, where it is somewhat split up, and ex- 

 hibits a tendency to leave the shale. On the fifth level the fissure is found 



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Fk;. 1.— Relation of formations to main fissure. 



in the first north cross-cut 182 feet from the main drift. Between it and 

 the shale the stratified limestone, which is here 30 feet wide, can be first 

 definitely distinguished. This band of limestone, which increases in width 

 as depth is attained, is always found on the hanging- wall side of the fissure, 



