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the fact that, this elevation lias been more or less interrupted, the surface 

 streams have devloped terraces and the caves near the Ohio and its older 

 tributaries have in some cases four or five levels, probably due to the 

 same cause. Only the lowest of these levels will contain water at the 

 present time. The four or five levels of passages in caves in the region 

 under discussion may have had other local causes, such as differences in 

 hardness or solubility, etc. It is not meant that all caves in this region 

 have several levels, for new caves are continually being formed. 



The bedding planes being planes of weakness, the cave will be broader 

 at the bedding planes than between them. (Fig. 1.) Softness or un- 

 usual solubility of a particular layer will cause a broadening of the cave, 

 while hardness or insolubility will result in a narrowing. If a cave is fol- 

 lowing some particular joint-plane, a cross joint (which perhaps carries 

 a larger or smaller stream) will cause a decided broadening, due to the 

 weak spot caused by the cross-joint. 



When a particular cave stream reaches temporary base level it will 

 cease downward cutting and begin eroding laterally. In this case the 

 stream is generally supplied with abundant abrasive material. In time 

 this will produce a cave with a sort of an inverted T-shape. (Fig. 2.) 

 Owing to the thinness of the layers, in time this will cause a collapse of 

 the sides and roof, such as has taken place in many parts of Wyandotte 

 Cave. (Fig. 3.) 



If such action takes place where two joints cross, the amount of rock 

 precipitated from the roof and walls will be enormous, producing such a 

 mound as Monument Mountain in Wyandotte, where a mound over one 

 hundred feet high has been formed. In the upper part of Shawnee Cave, 

 Lawrence County, the lateral erosion has been very great and in some 

 places in this and also in Wyandotte Cave, this tendency has resulted in the 

 collapse of the floor of an older passage above. Thus it will be seen that 

 the floor of an old cave will be apt to be rough and rocky instead of level, 

 although there are cases where the stream has suddenly found another out- 

 let, leaving an old cave with a smooth and firm floor. 



Most of the old caves and some of the younger do not follow straight 

 cardinal lines or have right-angled bends. In young caves this is due to 

 a tendency of the stream to straighten its course just as a surface stream 

 does, although hardness and solubility of the rock play a large part. (Fig. 

 4.) For example, if on one side of a joint-plane which a cave stream is 

 following, there is a particularly soluble spot, there will probably be a 



