204 l-I. L. FAIRCHILD POST-GLACIAL UPLIFT OF N. E. AMERICA 



lines. Force is also given to some unpublished figures by Professor Cole- 

 man. 



Professor Daly's altitudes for the east coast of Newfoundland are har- 

 monized with the isobases of the mainland only by regarding the island 

 as an inde^Dendent area of depression of about 600 feet, which implies a 

 separate ice-body. This carries the study over into meteorology. 



Criticism may possibly be offered that the isol)ases in the map are 

 too regular and parallel. Any irregularity in the direction and spacing 

 that would appear on a map of this scale would be due to irregular uplift 

 or local warping. Perhaps there is such in slight degree, but it would be 

 attributed to, or confused with, the local variation in height of the shore 

 features. However, the depth of terrane involved in the diastrophic 

 movement would appear too great to permit any sharp or local warping 

 of the surface, under either the hypothesis of compression and elastic 

 reaction or the conception of deep-seated flowage. Xo recent faulting has 

 been seen sufficient to produce any change in beach levels. The isobases 

 as drawn are, of course, somewhat generalized, but they represent the 

 facts in surprisingly accurate degree. The variations of the summit fea- 

 tures from the theoretic height, as indicated by the isobases, are given 

 in the tabulations below. These seem small when all the causes of alti- 

 tude variation are considered, as described above. 



Shorelines traced in the field and the isobases as drawn have no con- 

 sideration for mountain mass or valley deficiency. Apparently the sur- 

 ficial relief of the continent had no measurable effect on the amount of 

 uplift. This should be expected when it is remembered that the large 

 topography was pre-Glacial and isostatic equilibrium had long been estal)- 

 lished. 



The truth of the map is not dependent on the precision of a few^ sta- 

 tions, nor on the approximate figures for many stations, but on the gen- 

 eral accordance of the field data with the adjusted isobases over the great 

 area. 



Whatever correction the future may make in this map is more likely 

 to be in the increase of the amount of submergence and uplift, as we may 

 have to recognize some rise of the ocean level after land uplift had begun, 

 and also some lifting of the central part of the area while yet beneath the 

 ice-sheet. The writer has been conservative and careful not to overe^ti 

 mate, and he has the feeling that he has sometimes committed, in smaller 

 degree, the usual mistake of minimizing the height of the u])raised marine 

 plane. 



