Appalachian Geosyncline. 247 



but the margin of the vast volume eroded ; the land now hid- 

 den beneath the waters of the ocean must have been the chief 

 source of supply. In Maine, New Brunswick, and Nova 

 Scotia igneous activity is known to have prevailed in the 

 Devonian. The rocks of these provinces and of Newfound- 

 land, the latter structurally the eastern outpost of the con- 

 tinent, strike southeastward under the sea and toward the 

 region from which presumably came the sediments of the 

 Catskill formation. It would seem further that to such a zone 

 beyond the margin of the Coastal Plain of New Jersey must 

 we look to locate the source of the great volume of gray 

 quartzites which supplied the pebbles of the Skunnemunk 

 conglomerate. No adequate formation is known to the east 

 upon the land, but pebbles of Cambrian quartzite, thought to 

 have come from the east, are found in the Carboniferous con- 

 glomerates of Rhode Island and from that direction Wood- 

 worth thinks probably came the greater volume of material 

 which filled the Rhode Island basin. 



Lack of Relation of Appalachia to the Continental Shelf. 



The Control by the Continental Shelf on Paleogeo- 

 graphie Maps. 



The doctrine of the permanence of the continental platforms 

 has been held rigidly by many American geologists. Starting 

 in the past century with the recognition of the evidence that 

 the continents have never been the beds of deep oceans, but 

 have been flooded merely by shallow seas ; the corollary was 

 attached that consequently the beds of the deep oceans had 

 never been land surfaces. Yet this is not a necessary con- 

 sequence of the original proposition and has in reality no 

 similar direct evidence to support it ; except that basins must 

 have existed sufficiently large in former ages to hold the ocean 

 waters which were then upon the earth. But in the balancing 

 of losses and gains to which the surficial water is subject, it 

 appears probable that the gains have notably exceeded the 

 losses through geologic time. To a somewhat greater degree 

 than this the ocean basins can have increased in volume. 



As evidence opposed to the hypothesis of an unchanging 

 form of the ocean basins, many examples have been noted of 

 extinct and living faunas showing their closest affinities on the 

 opposite sides of present ocean basins, or isolated on oceanic 

 islands. The affinities are so special in some cases that many 

 even of the strongest adherents of the doctrine — that both con- 

 tinents and oceans have always been outlined in their present 

 relations — admit some degree of connection of former lands. 

 Yet where land bridges are not required, paleogeographic maps 



