APPALACHIAN BASELEVELS 275 



show that any such sufficient faulting has occurred. There are, it is true, 

 abundant faults to be observed in the approximately level district of the 

 shore belt, but these dislocations have had all traces of their original 

 relief completely effaced. Moreover, the passage of the plain to the liills, 

 although accomplished witbin a narrow belt, is in a measure gradual, 

 showing no signs of sudden change such as would be exhibited if tbe 

 conditions had been brought about by faulting alone. 



It has been suggested that while the Piedmont district remains at or 

 near its Cretaceous baselevel the country to the westward has been so 

 differentially uptiited that the highest point of elevation is the Alle- 

 ghanian field. To this hypothesis it may be answered that there is a 

 lack of evidence sufficient for its support. The only point where I 

 have been able to find any features which could be taken to afford such 

 evidence is in the section of the James River canyon from the base of 

 the Piedmont plain through the Blue Ridge and into the Alleghany field. 

 The occurrence of many rapids in the lower reaches of James river sug- 

 gests an uplifting action ; but these features go to show that the move- 

 ment which led to their formation was of relatively very recent age, and 

 that it affected in something like an equal measure all the section from 

 the sea border beyond the axis of the Shenandoah valley. 



Discussion of Hypothesis of Baseleveling and of River spacing 



While it can not be maintained that the evidence and arguments set 

 forth in this paper are sufficient to determine a conclusion against the 

 hypothesis of baseleveling as it is used to explain the approximate equal- 

 ity of summits throughout a considerably elevated area, it may fairly be 

 claimed that they go to show the need of a more penetrating inquiry 

 into the facts than has yet been essayed. When w^e consider that the 

 advocates of the hypothesis in question have not yet shown us a region 

 which has been and remains effectively baseleveled ; when, moreover, we 

 note that the changes in the relative level of the sea and land are not 

 only frequently extensive, but evidently occur with a speed which is 

 rapid in relation to the rate of down-wearing of the land, we may indeed 

 begin to doubt the validity of the hypothesis that any such wide 

 area as the eastern portion of this continent could ever have been so far 

 worn down throughout its extent as to approach in aspect the suppositi- 

 tious plain which this view demands. There can be no question con- 

 cerning the value as to the control which a baselevel of erosion exercises 

 over the work of a river. The point yet to be determined relates to the 

 efficiency of river work in bringing about the uniformity of hights in a 

 mountain-built district. It appears to me that in the fields which I 



