crane: '-'horsebacks in the KANSAS COAL MEASURES. 



H7 



row, averaging perhaps less than five feet as they are found in the 

 coal. They generally pass through the coal and into the shale 

 above, often reaching almost to the surface, but sometimes thin- 

 ning out to a mere fissure with no apparent thickness only a few 

 feet above the coal. At other times they do not pass entirely 

 through the coal from below, while still again in much rarer cases 

 they seem to hs passing downwards from ab3ve. Fig. i. The 

 downward extent of the fissures in most cases is entirely unknown 

 as coalmining operations do not follow them much below thecoai 

 itself- 



The fissures often bifurcate, or in some cases split into more 

 than two branches, in both horizontal and vertical directions. 

 Their hade is generally but a few degrees from the vertical, and 

 perhaps a large majority of them hade less than thirty degrees from 

 the vertical, but occasionally one is found making an angle of as 

 high as eighty or eighty-five degrees. 



Nature of the Walls. — The walls of fissures are usually rough 

 and ragged, but sometimes are smooth and polished presenting 

 well formed slickensides. This property is even present in the 

 walls of the coal seam itself in some instances, although not so 

 strongly marked as the fissure walls in the shales and clays. 

 Usuall}' the coal walls are rough and jagged with th^ irregularities 





Fig. 3.— Hor.sebark showing t)ulji:lii,u; of stratii duo to liiteral compi-ussioii. 



