560 SHAW: NEW AREA OF CARBONIFEROUS 



somewhat less rate than the dip of the rocks, and that there 

 is good reason for believing that erosion has been acting contin- 

 uously on southern Illinois, with the exception of those times and 

 areas when and where deposition was not in progress, seems to 

 accord with the inference that deposits of the embayment or 

 Coastal Plain possibly once extended far north of their present 

 limits. In any case it is evident that the northern border of 

 these deposits is now being driven southward and that the sur- 

 face features along the southern side of the range of hills are those 

 of a peneplain that has been long buried and only recently un- 

 covered, and which, as shown by outcrops and well records at 

 Brookport, Metropolis, Cairo, and other places, slopes southward 

 28 to 32 feet to the mile. 



