14b 



KANSAS UNIVERSITY QUARIKRLV. 



States. In fact there are few, if any, coal-mining localities known 

 in America where they do not occur. In our own state they have 

 been studied by the writer in Cherokee and Crawford counties only^ 

 so that it is not known to what extent they may be found in the 

 other mining districts of the state. 



NoMENCLAiURK. There seems to be a slight lack of harmony in 

 the usage of the above mentioned terms, especially in different 

 states. For instance, in Kansas the term "horseback" is applied 

 strictly to clay-fiUed, almost vertical fissures which pass through 

 the coal. In Pennsylvania such clay-filled fissures are called 

 "clay veins." Again in the coal fields of this state a dipping 

 down or a bulging up of the strata from above t)r below the coal, 

 especially the former, is called a "roll in the slate" of the roof. 

 This phenomenon is given the name "horseback." "nip," "want,"" 

 etc., in the Pennsylvania collieries. The nomenclature adopted 

 by the Pennsylvania miners and geologists seems the most applic- 

 able and will therefore be used in this paper. 



I'M";-. :i.— Horseback sliowiiifi the u])\var<l bul.L;iii?r of the coal and shah'. 



Forms of the Fissures. — The "horsebacks " or "clay veins" of 

 Kansas seem to be clay-filled fissures formed after the coal was 

 consolidated. They trend in many directions with apparently no 

 regularity. So far as has yet been observed the direction of indi- 

 vidual fissures is wholly irregular, but a line trending northeast 

 and southwest seems to strike a larger proportion of them than 

 would a line in any other direction. The fissures usually are nar- 



