108 THREE CRUISES OF THE “ BLAKE.” 
varied than that of continental areas. As a general rule we 
find that the continental masses form platforms sinking quite 
rapidly into the adjoining oceanic basins. The hundred- 
fathom line may extend far out to sea in some cases, as, for 
instance, in the northwestern extremity of France, where it unites 
Great Britain and France. On the east coast of the United 
States an extensive plateau — the continuation, in other words, 
of the continent below the surface — follows the hundred-fathom 
line along our southern coast to the extremity of George’s 
Bank, expanding again farther north, off the coasts of Nova 
Scotia and of Newfoundland, so as to include Sable Island Bank 
and the Great Banks of Newfoundland within the true conti- 
nental line. In the case of the West India Islands, this line 
discloses a connection between adjoining islands which the mere 
study of the land map would fail to show. But the hundred- 
fathom line is simply the edge of the continental plateau along 
which the detritus brought from the continents by its rivers is 
deposited. Upon its slope the fauna characteristic of any 
region extends into deep water, gradually becoming modified 
in its character by the temperature of the region into which it 
finds its way. Beyond this hundred-fathom line there is usually 
a very rapid descent into deep water. This line may indeed be 
considered as the true continental outline, the edge of the shelf 
which forms the continuation of the continental masses, below 
the surface and beyond those shore lines which we are accus- 
tomed to consider as the true boundary between land and water. 
