56 



Indiana University Studies 



Thus, a total of approximately 5,200 acres or 8 square miles 

 drains into the holes in the American Bottoms". 



It may be noted that the ravines which are re-excavating 

 the pre-g-lacial valley to the west and southwest of the old 

 lake basin are taking away the material at a very rapid rate. 

 The ravine in the southwest portion of the northwest quarter 

 of section 26 is a great gully or series of gullies, near its 

 abrupt head, eating directly back up the line of the pre-glacial 

 valley. It would appear that this ravine, which at present 

 is so rapidly reaching into the outwash sand by headward 

 erosion, may in time tap the streams leading into the sub- 

 terranean openings, and thus divert the drainage approxi- 

 mately thru the old channel to the present Cliffy Creek 

 (Fig. 10). While this is a suggestive possibility, it will prob- 

 ably never happen. The present streams of the basin at their 

 subterranean inlets are approximately at an elevation of 620 

 feet, while the elevation of the ravine where it crosses the 

 road considerably more than a mile to the southwest is only 

 20 feet lower. This difference is not enough to give the 

 advantage necessary for piracy, since the small stream would 

 probably require much more than 20 feet fall in the distance 

 it would have to go. It would appear that the subterranean 

 passages must persist, unless they should become thoroly 

 choked, which is unlikely. 



When the inlet-sinks of the ''American Bottoms" basin 

 were flrst examined it was thought that the Beech Creek lime- 

 stone would certainly be visible, and the fact that nowhere is 

 there the least vestige of it exposed at the surface at any of 

 the openings gave cause for considerable surprise. These 

 openings can be entered for only a short distance. It was 

 found, however, that the water has to pass over logs, sticks, 

 and other trash that has been lodged in the openings near 

 the entrances, and it was found further that the water de- 

 scends thru the trash very sharply, and probably within a 

 short distance from the entrances reaches the Beech Creek 

 limestone. 



Just why the water that enters the openings has not cut 

 down to the level of the limestone passageways is not alto- 

 gether clear. Only two suggestions adequate to explain this 

 condition occur to the writer from observations made in the 

 field. At the opening much foreign material is carried in 



