Nansen's Continental Oscillations— Spencer. 233 
places make this highly probable and at some places — e. g. the 
Fosse de Cap Breton, the Congo submarine canyon, the Bottomless 
pit — there seems no other feasible explanation to be found. Some 
drowned valleys on the American side of the Atlantic seem per- 
haps to give still better evidence of such a recent elevation. Even 
if we admit that the long submerged channel of the St. Lawrence 
river might possibly, although not probably, have been reopened 
by submarine glacial erosion, * * * ^ seems also highly im- 
probable that the drowned valleys of the Newfoundland bank, far 
from land have been reopened by submarine glacial erosion. The 
drowned valley of the Hudson river cannot possibly have been 
reopened by submarine glacial erosion. It is too long, and narrow, 
and too deep. Its narrow and well defined channel, cut in the 
extremely level continental shelf, seems to prove that the latter 
has comparatively recently been elevated into dry land. Prof. J. 
W. Spencer has described a great many drowned valleys along the 
coasts of the West Indies and the United States south of the 
drowned Hudson valley. Although Spencer's description of the 
drowned valleys may often be based on too few and scattered 
soundings, to be absolutely certain, there are a good many sub- 
marine features in this region which cannot easily be otherwise 
explained, and which indicate vertical oscillations of great ampli- 
tude, of the shore line, as Prof. Spencer has pointed out in such 
an ingenious way. According to his investigations the drowned 
valleys of the continental shelf, as well as the valleys of the coast, 
have been filled and reopened several times according as the shelf 
was submerged or elevated into dry land. * * * The shelf can- 
not have been covered by much deposit after the last submergence. 
* * * Thus * * * there is weighty evidence that the 
drowned valleys have been sculptured after the formation of the 
continental shelves, and that consequently the latter have been dry 
land after formation, * * * if at some places * * * also 
at least in neighboring regions; for considering that the continen- 
tal shelves have retained practically the same level mutually, the 
oscillations of level cannot have been due to quite local tectonic 
movements." (pp. 191-192.) 
Of the Stability and oscillations of the shore line, Dr. 
Nansen says that the well developed continental shelves of 
the earth prove that the general level of the hydrosphere 
must have remained near its present position during long 
recent geological periods. This is illustrated by Sir John 
Murray showing that 40 per cent of the continental area is' 
situated between 200 metres above and below the present 
sea level. But the sea level has not remained stationar\-. 
as it has been conclusively proved to have oscillated be- 
