174 PROCEEDINGS OP THE AMERICAN ACADEMY. 



between the remnants above a submarine platform and the monadnocTia 

 rising above a subaerially carved peneplain. The burying by slow sub- 

 mergence would tend to protect from decay the sea cliffs and benches, so 

 that when re-elevated and divested of their sedimentary protection, the 

 marks of sea action would show marine origin, at least in part. A de- 

 pressed peneplain with its monadnocks would also show cliffs and benches, 

 if it remained in its descent at one level for a time sufficient for cutting. 

 Features of shore development must not then be considered as distin- 

 guishing between monadnocks and marine remnants. 



The vital question is how far the cover extended inland, and what point 

 the former shoreline reached. Inside this limit all differential erosion 

 remnants will have been formed entirely by subaerial degradation, while 

 on the seaward side of the line the sea will have had more or less to do 

 with their formation. After the form of the old shoreline has disap- 

 peared, and the coastal plain sediments been more or less completely 

 stripped off, the evidence for the former greater inland extension of the 

 cover will lie in the arrangement of the streams. The area formerly 

 covered will show superposed streams and less perfect adjustment of 

 rivers to structure than is found beyond the limits of the former 

 shoreline.* 



Coastal Inequalities. — IMany writers have ascribed all inecpialities of 

 the coast to differential erosion of the sea. Even as late as 1882, Prof. 

 A. II. Green implies that all bays and other coastal inequalities are due 

 to " the hardness and structure of the rocks." f The tendency in America 

 of later years has been to ascribe all inequalities of the shoreline to the 

 drowning of subaerially carved forms. "While submerged topography will 

 account for the greater i)art of such irregularities, we must not entirely 

 leave out of the consideration the action of the sea. 



The agents of the sea are the waves. $ tides, and currents. Writers 

 differ widely in what they attribute to each of these three agents, and a 

 discriminating study of the work of the three should be made by some 

 careful observer. The present writer is inclined to attribute the attack 

 of the sea largely to the waves, and its transporting action largely to the 

 tides and currents. , 



* See Messrs. Davis and Wood, Proc. B. Soc. Nat. Hist., 1889, XXIV. 399-410; 

 Professor Davis, Lond. Geog. Jour., 1895, V. 128-138. 



t Physical Geology, 577. 



} For the method of wave attack see Gilbert, Mon. I., U. S. G. S., Chap. II., 

 •with references ; Lyell, Principles of Geology, 11th ed., 1872, 1., Chaps. XX.-XXII. ; 

 LeConte, Elements of Geology, 2d ed., 1882, 31-43; Penck, Morphologic der Erd- 

 oberflache, II. 460-497, with references. 



