Baselevel of Erosion. 6 
~I 
where glaciation has interfered with their normal development 
or masked their completed form. 
THE PROBLEMS AND THE DATA. 
Since the southern Appalachian province, as above defined, 
has stood above sealevel throughout the whole of the period 
whose history is under consideration, that history must be read 
in the topographic forms developed during the process of sub- 
aerial degradation and in the adjustments of drainage to chang- 
ing conditions. 
The fundamental conception, in the interpretation of the his- 
tory of a region from its topographic forms, is the baselevel of 
erosion. The formation of a general baselevel peneplain implies 
the long continuance of certain well defined conditions, so that 
wherever the presence of such a peneplain can be established 
the former existence of these conditions may be safely inferred ; 
also it can be formed only near sealevel; hence by contouring 
the present remnants of a baselevel peneplain the contour at any 
point represents very nearly the algebraic sum of all changes in 
altitude which that portion of the plain has suffered. 
In the southern Appalachian province the more or less per- 
fectly preserved remnants of two baselevel peneplains have been 
mapped and their deformations represented by contours; the 
conditions implied by these baselevels have been inferred ; their 
probable correlations with the contemporaneous sedimentary 
deposits indicated ; and finally the development of the drainage 
has been traced through a complex series of adjustments upon 
the repeatedly deformed surface to its present mature location. 
Parr J—PuystocrRapuic DEVELOPMENT. 
CLASSIFICATION OF TOPOGRAPHIC FEATURES IN THE PROVINCE. 
The southern Appalachian province has certain topographic 
features common throughout its entire extent. They are so 
modified by local conditions that their identity in different por- 
_ tions of the province would scarcely be recognized by the casual 
| observer, but to the student of geomorphology they stand out as 
__ the most prominent feature of the landscape and he reads from 
them many chapters in the history of the province during post- 
| Paleozoic time. With our present information we are able to 
| classify these topographic forms and to trace with considerable 
| 
| 
