362 
The more intricate and complex an individual history, the more fascinating 
it is to the student of physiography. 
Problems pertaining to drainage are by no means few in southern Indi- 
ana. The division of the Illinois glacial lobe, or rather the projection of 
two lobes into southern Indiana, left a large triangular area of about 
5.000 square miles in extent, untouched by the ice. Where the pre-glacial 
streams came against the eastern margin of the western lobe there was 
much derangement of the pre-existing drainage, especially the smaller 
streams. But it is in the unglaciated area that stream development and 
adjustment have gone on unhampered. It is here that we find some of the 
finest examples of adaptation of the drainage direction to the geologic struc- 
ture and the topographic conditions. The details of drainage development 
involve intricate cases of underground drainage with diversion of the 
waters from original surface streams to other streams by subterranean 
piracy. Such a condition would result only in a special limestone region 
where both geologic and topographic conditions are favorable. But the sub- 
ject matter of this paper is a presentation of the broader features which 
permit certain stream adjustments to take place rather than a considera- 
tion of the full details of drainage phenomena and topographic form. A 
part of the subject matter, however, is concerned with the general consid- 
erations of a rather odd case of stream gradient and also with tne details 
of a notable case of stream piracy. but the cases are presented as illustrative 
of stream adjustments to the geologic and topographic conditions which 
characterize the particular region here chosen. 
The area from*the Muscatatook River along the southern boundary of 
Jackson County to the Ohio River on the south presents a number of rather 
striking physiographic features. The chief one of these is the southern 
and best developed portion of the Knobstone escarpment, the most prominent 
relief feature in Indiana. The area embraces western Scott, western Clark, 
Washington, Floyd, and Harrison counties. This is the area shown by the 
general map accompanying this paper. It is essentially the Knobstone 
cuesta and contiguous territory near the eastern margin of the unglaciated 
portion of southern Indiana. The topographic map is a bit of detail within 
the larger area shown by the general map. The area is chosen here to 
illustrate the importance of geologic structure in the development of topo- 
graphic forms, and also to present one or two illustrations of adaptation 
of drainage to geologic structure and topographic condition. The special 
factors concerned in these phases of physiography will be presented in some 
detail. 
DEFINITION OF GEOLOGIC STRUCTURE AND TOPOGRAPHIC 
CONDITION. 
Frequent mention is made in this paper of geologic structure and topo- 
graphic condition. There is no intention of using these terms in any other 
than the ordinary sense, yet it is well to give an exact statement of the 
meanings of the terms as used in the present discussion. The definition 
