253 
eradually higher, owing to the resisting nature of their lowest beds. The 
distance from the Knobstone escarpment to the highest hills capped with 
the Mansfield standstone is about thirty miles. 
(b.) The structure of each of these topographic features where crossed 
by the section is essentially the same in different stages of development; 
j. e., that of a dissected plateau, sloping gently to the west. In the east- 
ern, or Devonian limestone plateau, in the region of the Ohio, dissection 
has scarcely begun, as none except the streams flowing directly into the 
Ohio have deep gorges, and these are only from one-half to one and a 
half miles long; in the middle, or Knobstone plateau, dissection has pro- 
gressed much further than in the eastern one, while the western or Mans- 
field sandstone plateau has been completely dissected by its streams. 
It is possible that this peculiarity in the amount of erosion that has 
taken place in these different plateaus is the result of the character and 
former upward extension of the overlying formations in each case. 
(c.) The top of the eastern plateau where crossed by the section is 
_800 feet above the sea, that of the middle is 820 feet, and that of. the 
western 880 feet above tide, while but a short distance to the north or 
south the topographic sheets show the elevations of these plateaus to cor- 
respond even more closely. 
These closely corresponding elevations point strongly to the conclu- 
sion that the present topography of southern Indiana has developed from 
an old base-level. The present topography, however, might have been de- 
veloped from a plain of deposition, or a combination of the two. 
THE KNOBSTONE GROUP IN THE REGION OF NEw AtpBany. By J. F. Newsom. 
During the field season of 1897 the Indiana University Geological Sur- 
vey undertook the delineation of the upper and lower limits of the Knob- 
stone group, and working up of the general geology of that particular 
formation. Work was begun in the extreme southern part of the State. 
It is with only a few of the points of interest that were developed in that 
region that this paper deals. 
