64 THREE CRUISES OF THE / BLAKE." 
While there is thus undoubted evidence that a great part of 
the shore line of the northeast extremity of South America has 
been washed away, there is also evidence that the lines of the 
bank connecting the lesser West India Islands have been built 
up by agencies similar to those which have formed the Yucatan 
and Florida banks, except that these latter have been formed 
around the volcanic islands or folds which extend along the east- 
ern edge of the Caribbean Sea. In some cases these banks have 
been elevated since the ekisting condition of things came about ; 
in others their elevation dates back to the period when the 
separation of the Caribbean from the Pacific took place, at the 
time of the closing of the Isthmus of Panama. Evidence of 
this action is found in the elevated coral reefs and the raised 
earlier tertiary and later cretaceous deposits of the West Indies 
and Central America. 
Nowhere do we find better examples than in the West India 
Islands of the formation of submarine banks in connection with 
volcanic peaks. A great number of peaks of voleanie origin 
have risen nearly to the surface of the sea, or above it, and 
serve as the foundation of great submarine or littoral banks. 
It is well known, also, that the “Challenger” and “ Tuscarora” 
soundings have developed a number of submarine elevations, 
covered by deposits of pteropod and globigerina ooze, and these 
deposits form extensive banks which serve as foundations for 
barrier reefs and atolls, while the volcanic substratum has been 
completely hidden. In the West Indies, as at Martinique, there 
are voleanie peaks rising to a height of over four thousand 
feet; on their windward side are extensive submarine plateaux, 
formed, I imagine, by agencies similar to those to which we 
ascribe the formation of the Yucatan and Florida plateaux. 
Whenever such plateaux have reached on their windward side 
the level at which corals prosper, there coral reefs spring up 
and flourish. Side by side with such conditions we find pla- 
teaux at lower levels, under a greater depth of water, covered 
only by the invertebrates living upon their surface, —as is the 
case, for instance, in the northern extremity of the plateau of 
the Grenadines. These plateaux have probably never risen to 
the surface. We have also the still older phenomenon of such 
