100 GLEANINGS FROM NATURE. 



animals bereft of the sense of sight. To him, there- 

 fore, the under-ground journey promises much more 

 than to the ordinary observer who makes it mainly for 

 the novelty and the scenery which it affords. 



The Sub-carboniferous Limestone area of southern 

 Indiana contains many sink-holes and caves within 

 its bounds. This area is, for the most part, embraced 

 in the counties of Owen, Monroe, Lawrence, Wash- 

 ington, Orange, Harrison and Crawford. Going 

 southward from the center of the State, the sink- 

 holes first become a prominent feature of the surface 

 in eastern Owen and western Morgan counties, and 

 are found in numbers thereafter, in the area mentioned, 

 until the Ohio River is reached, beyond which, in 

 Kentucky, they are said to be still more numerous, in 



many portions of that State averaging 

 Sink-holes. rp, . , to 



100 to the square mile. Ihese sink- 

 holes vary much in size, sometimes being but a rod or 

 two across, and again embracing several acres in 

 extent. They are, for the most part, inverted cones 

 or funnel-shaped cavities, and, where small, usually 

 have the sides covered with a matted growth of vines 

 and shrubs. Where larger, trees of varying size are 

 often found growing from the scanty soil on the sides 

 or from the bottom of the sink. If one will examine 

 closely the lowest point of a sink-hole, he will usually 

 find a crevice or fissure through the limestone, or 

 sometimes a large opening which, if it. be possible to 

 enter, will be found to lead to an under-ground cavity 

 a cave. 



Both sink-holes and caves not only owe their origin, 

 but usually their entire formation, to the slow, unceas- 



