112 THREE CRUISES OF THE “ BLAKE.” 
St. Eustatius to Nevis, and Barbuda to Antigua, and thence 
extends south so as to include Guadeloupe, Marie-Galante, and 
Dominica. The five-hundred-fathom line thus forms опе 
bank of the northern islands, and leaves but a narrow channel 
between it and the eastern end of the five-hundred-fathom line 
running round Santa Cruz. Santa Cruz is separated from St. 
Thomas by a channel of forty miles, which thus forms a basin 
with a maximum depth of over twenty-four hundred fathoms. 
It is united with Porto Rico by a submarine ridge with a depth 
of about nine hundred fathoms. This plainly shows its con- 
nection with the northern islands of the Caribbean group, 
rather than with St. Thomas; yet, as is also well shown by the 
geographical relations of its mollusca, their affinities are rather 
with Porto Rico and that group of islands than with the Carib- 
bean Islands. This may be explained by the existence of an 
easterly current setting along the shore, or of a former land 
connection with Porto Rico, still indicated by a ridge discovered 
by the “ Albatross,” running from Santa Cruz to Porto Rico, 
having a maximum depth of nine hundred fathoms. The five- 
hundred-fathom line again unites, in one huge spit extending 
northerly from the mouth of the Orinoco, all the islands to the 
south of Martinique, leaving Barbados to the east, and a narrow 
passage between Martinique and the islands of Dominica and 
St. Lucia. 
At the time of this connection, if it existed, the Caribbean 
Sea was connected with the Atlantic only by a narrow passage 
of a few miles in width between St. Lucia and Martinique, by 
one somewhat wider and slightly deeper between Martinique 
and Dominica, by another between Sombrero and the Virgin 
Islands, and by a comparatively narrow passage between Jamaica 
and Hayti. The hundred-fathom line connects the Bahamas 
with the north-eastern end of Cuba; the. five-hundred-fathom 
line unites them not only with Cuba, but also with Florida. 
The Caribbean Sea, therefore, must have been a gulf of the 
Pacific, or have been connected with it by wide passages, of 
which we find the traces in the tertiary and cretaceous deposits 
1 Between Martinique and Dominica a peak in mid-channel was found within 
eighty-five fathoms of the surface. 
