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pied by the Mitchell limestone is dotted cvei* 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 jointod but fine 

 grained. The grnmul'wator is compelled to traverse the joints rather than 

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

 the more extensive development of caves in the Mitchell tluMi in tli<5 -Salem 

 limestone, since the two must Ite about enually soluljle. It is the con- 

 centration of solution aldug joints .•uid bedding planes that gives rise to 

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

 relatively impervioiis layers to serve as cave tloors. Neither of these 

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

 drainage, which has l)een supplied by tlie intrenching of the main streams 

 as explained above. 



