barrell: movements of the strand line 417 



determination of the sea level in latitude 40° for each stage of 

 the ice retreat. This represents the movements in a belt be- 

 yond the terminal moraines. The figures obtained indicate 

 that the Coastal Plain was higher than at present and rising, 

 the sea sinking, during the retreat of the ice. These effects are 

 of an opposite character to that produced by the addition of 

 water to the ocean during deglaciation. 



This argument by itself rests upon a structure of hypothesis 

 and carries but little weight, but independent lines of evidence 

 pointing in this direction will now be considered. Analysis of 

 the data obtained from borings in the channels of the Hudson 

 shows that a cycle of emergence and subsidence has occurred 

 since the retreat of the ice, but not over 200 feet as a maximum 

 above present level. Evidence that a minor cycle of emergence 

 and submergence has occurred along the shores of southern 

 New England and the South is also found. The evidence for 

 a rapid cycle of post-glacial emergence of considerable amount, 

 involving a tract beyond the limits of glaciation, now drowned, 

 is perhaps best given by the distribution of plants along the 

 Atlantic shore from New Jersey to Newfoundland. From the 

 work of Britton, Hollick, and especially Fernald, it is shown that 

 118 species of plants belonging to the southern Coastal Plain 

 floras are known from widely isolated outlying stations along the 

 coastal strip of New England and the iMaritime Provinces. 

 Newfoundland, however, furnishes the most remarkable and 

 convincing evidence. Fernald shows that neither winds nor 

 currents nor migrating birds can be competently invoked in 

 explanation. A remaining hypothesis is that for a time after 

 the last retreat of the ice the Coastal Plain stood higher, margined 

 the continent as far at least as Labrador, and permitted the 

 spread of the Coastal Plain flora. The character of the flora 

 suggests that the migration to the present isolated localities 

 must have taken place during a period of climate even warmer 

 than the present and therefore at a time after the ice-sheets 

 had given up their water. The hypothesis that the emergence 

 was due to withdrawal of w^ater during glaciation must there- 

 fore be ruled out. 



