tendency is accentuated wlien the pirate is favored by the dip of the 

 rocks, but frequently occurs in spite of the dip in cases where the 

 dip is gentle. It is probably true that the only essential of such capture is 

 that two streams lie one higher than the other in a region of soluble rocks 

 sufficiently close to each other to permit the final entrance of some of the 

 water of the one to the other. Examples of such piracy are by no means 

 wanting in the Bloomington region. 



Fig. 12. A distant view of the Leonards Mill locality (Figs. 8 and 9), sliowing 

 the form of the valley. The water from the Shirley Spring (Fig. 7) crosses the 

 foreground. 



In order to make these specific cases fully intelligible it is necessary to 

 refer to some length to the physiographic history and conditions of the 

 region. The well preserved ploin west of Bloomington appears to be a very 

 early Pleistocene peneplain. This plain extends at about the same altitude 

 throughout the extent of the map, except that it is visibly beveled toward 

 the m;ijor drainage lines, as will appear later. The peneplain is much dis- 

 sected in the northeastern, southeastern, and western parts of the (piad- 

 rangle. There are many monadnocks to be fomid along the old divides or 

 near the headwaters of some ot the minor streams, rising from a little 

 over a hundred feeL to two hinidi'od feet or more nliove this old plain and 



