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pied by the Mitchell limestone is dotted over with sinkholes, and the hill- 

 sides along the larger streams abound in springs and entrances of caves. 

 Some of the caves, such as Marengo and Wyandotte, have attained wide 

 fame. The Mitchell is, as indicated above, conspicuously jointed but line 

 grained. The groundwater is compelled to traverse the joints rather than 

 the pores of the rock, and it is this, in the writer's opinion, that has caused 

 the more extensive development of caves in the Mitchell than in the Salem 

 limestone, since the two must lie about equally soluble. 11 is the con 

 centration of solution along joints and bedding planes that gives rise to 

 caves. The Mitchell has both an elaborate system of joints and numerous 

 relatively impervious layers to serve as cave floors. Neither of these 

 conditions would avail, however, without the third condition, adequate 

 drainage, which has been supplied by the intrenching of the main streams 

 as explained above. 



