694 ABSTRACTS OF PAPERS 



Further, the capacity to do critical work implies training, and among the ele- 

 ments of training I would place much importance on the unpleasant experience 

 of being compelled by the force of new evidence to give up an opinion that 

 one has held for a year or more with satisfaction; for this shows the subject 

 that his mind is really open to change when good reasons for change are 

 found. Experience of this kind is seldom provided in systematic instruction. 

 It does not often come from one's own intention. It is best supplied by the 

 work of one's colleagues, to whom one ought therefore to feel grateful as 

 occasion offers. But gratitude of so dutiful a kind may well be accompanied 

 by a certain amount of personal discomfort. It would not be sincere on my 

 part to say that gratitude in this case is an unmixed feeling. The case re- 

 sembles that of a patient who swallows his medicine, in spite of its unpleasant 

 taste, because he has confidence in his physician. There is no one among our 

 members from whom I, as a patient, would more confidently swallow an un- 

 palatable dose in the expectation of its leading to a cure than from Dr. 

 Barrell. 



Mr. N. H. Darton : I have given much attention to the physiographic de- 

 velopment of the Piedmont slope in Maryland and Virginia and do not feel 

 convinced that the region shows evidence of having been planed or terraced by 

 the ocean. It seems more likely that the features described by Dr. Barrell 

 are parts of slopes representing various stages of subaerial planation of Ter- 

 tiary and later times. In a few places to the eastward there was some in- 

 cursion of the sea during Chesapeake time, and there was extensive deposition 

 of Lafayette and Pleistocene formation and later deposits, most of which have 

 since been removed. I should mention in this connection that the Lafayette 

 and Pleistocene deposits near the western margin of the Coastal Plain are not 

 of marine origin, but are fluviatile and estuarine products. 



In general it is unsafe to regard rounded hills of similar height as repre- 

 senting a terrace, for such hills are in process of degradation, and since Ter- 

 tiary and early Pleistocene times have greatly decreased in altitude, and the 

 approximate coincidence in height of scattered hills of hard and of soft rocks 

 does not necessarily define a terrace. 



Professor Barrell replied as follows : Dr. Leverett has asked what relation 

 the Hudson gorge may hold to the Sunderland terrace. In reply, I would say 

 that this investigation shows no new facts on which to base a relationship. 

 It is thought from glacial erratics dropped by floating ice on the Coastal Plain 

 01' Maryland that the Sunderland terrace was covered by the sea during an 

 early epoch of glaciation. The terrace as shown on the Connecticut shore has 

 been largely destroyed by erosion, yet fragments remain sufficiently intact to 

 show level tops and integrate into an even sky line. Therefore a continental 

 glacier was not here at the time of wave planation. The subaerial erosion 

 features now submerged below present sealevel can be divided into the mature 

 valleys which now constitute such drowned areas as Long Island Sound and 

 Chesapeake Bay and the deep and narrow inner gorges. From the degree of 

 their physiographic preservation these features do not impress one as older 

 than the Sunderland terrace, so that the suggestion from this comparison is 

 for a Pleistocene age. 



Prof. D. W. Johnson has raised several points. First, in regard to the sig- 



