160 PROCEEDINGS OP THE AMERICAN ACADEMY. 



Episodes of depression occurring after those of elevation or alternating 

 with them, if they occurred, must have been of short duration, as well as 

 those of elevation, for there is no indication that the development of 

 coastal features has continued for a great length of time at any level 

 since that at which the adolescent to mature dissection took place. A 

 possible exception to the above is the short cycle represented by the rock 

 bench called by Dr. Reusch "the coast plain " (Nor., 6, B; 45, C, D ; 

 46, C; 48, B ; 49, A; 53, C ; 56, A, B). From the form it is impos- 

 sible to tell whether this was cut before or after the deepest valley 

 dissection, shown by the present fjords. In his English summary (the 

 writer is not able to read the Norwegian paper) Dr. Reusch says, " It 

 has been worked out in periods previous to the glacial period, and in the 

 intervals of that time." * If it is later than the deeper dissection some 

 traces of the material filling the bays should be found, though the glaciers 

 would have carried off most of the loose detritus. 



Volcanic and Climatic Accidents. — In this paper the shore features 

 that result from the accidents, volcanic and climatic, which are not an 

 essential part of the normal cycle, are not considered in detail. With the 

 general scheme of the normal development of shorelines following eleva- 

 tion and depression in mind, a study of the accidental interruption of the 

 normal succession can profitably be made. The volcanic features as 

 shown in Etna (Italy and Sicily, 269, 270, etc.), and Santorin (Fouque, 

 Santorin et ses eruptions, Paris, 1879) and the glacial features as seen 

 on Oland island (Swe., 17, 22), in Boston harbor (C. S., 337), Green- 

 land, and Alaska ; and the arid coasts of Arabia and the shores of the 

 Red sea, etc., all furnish an attractive field for special study. 



Geographic and Paleontologic Criteria. — By the emphasis laid on ge- 

 ographic criteria for the recognition of change of level and time since the 

 initiation of a new cycle, it must not be inferred that the writer implies 

 any lack of confidence in the value of evidence from the position of life 

 forms. Geography and paleontology should go hand in hand in showing 

 past changes of level, as where one fails the other may avail. While his- 

 torically paleontology has had the lead, perhaps the more natural leader 

 would be geography ; then the indications, given by the inductive study 

 of the form of a region, may be confirmed by its contained fossils. 



Ideal Areas. — Two areas of strongly contrasted conditions are taken as 

 types. In each area the development of coastal forms has been consid- 

 ered to have advanced to late adolescence or into maturity in the previous 



* See references. 



