SUMMARY AND CONCLUSION. 
This paper conforms to the principle that physiography is explanatory 
rather than a mass of descriptive matter. The map, especially the topo- 
graphic map, takes the place largely of the descriptive matter. The purpose 
of the paper is to show specifically the responsibility of the geological 
structure in the development of topographic form, especially in a regional 
way, and also to show the importance of the combined geologic structure 
and topographic condition in drainage adjustment. It deals with the knob- 
stone cuesta region lying between the Muscatatuck and Ohio Rivers near 
the eastern margin of the driftless area of southern Indiana. The details 
defining, describing, and explaining the geologic structure and topographic¢ 
condition take up a relatively large proportion of the paper. Details are 
given showing how the particular lihtologic units with their regional west- 
ward dip are important conditioning factors in giving rise to topographic 
forms, and that the topographic condition in the stages of youth and ma- 
turity are lagely dependent upon lithology and structure. Other condition- 
ing factors scarcely less important are the so-called time factors, such as 
regional elevation and depression, warping and tilting, glaciation, and cli- 
matic changes. Active factors, weathering and erosion, are given no detail, 
but their activity is tacitly assumed and occasionally referred to directly. 
The development of the Scottsburg Lowland, or the Eastern Lowland of 
Newsom, is given an explanation somewhat different from any heretofore 
advanced. <A local peneplain after having been normally developed is sub- 
jected to further erosion by a peculiar sort of rejuvenation brought about 
by glaciation. The Ohio River has been formed from a number of smaller 
streams which were near the margin of the glacial ice at its farthest ad- 
vance. This stream dispossessed a minor stream in the vicinity of New 
Albany, and on account of its ability to reach a much lower gradient than 
the smaller stream, intrenched itself in the local peneplain developed in the 
area of soft rocks. Tributary streams have since partially destroyed 
the local peneplain rejuvenated in this manner. Such a rejuvenation is 
here called static rejuvenation. 
The peculiarity of the streams flowing east and north from the Knobstone 
escarpment is described. DBlue River is discussed in some detail. since it 
is representative of all the streams on the back-slope of the cuesta. Its 
peculiar, fairly uniform gradient demands explanation. It is shown that 
such a gradient is the result of a complex set of conditions, in which lith- 
ology, uplift, and static rejuvenation play their parf. 
Finally the details of the piracy of Muddy Fork of Silver Creek are 
given. It is shown that this piracy is a direct result of the geologic and 
topographic condition along the Knobstone escarpment. ‘This piracy is 
not an instance of a single case, but consists of successive piracy 
wherein a large number of tributaries belonging to a single stream system 
are annexed to the drainage system of an invading stream. It is noted that 
the conditions are highly favorable for the piracy to continue, and that 
eventually the larger part of Muddy Fork of Blue River will be taken over 
