AMERICAN DREDGINGS IN THE CARIBBEAN SEA. 
363 
the position of more or less important islands which must have 
once existed between the Mosquito coast and Jamaica. On ex- 
amining the 500-fathom line, we thus find that Jamaica is only 
the northern spit of a gigantic promontory, which once extended 
towards Hayti from the mainland, reaching from Costa Rica to 
the northern part of the Mosquito coast, and leaving but a com- 
paratively narrow passage between it and the 500-fathom line 
encircling Hayti, Porto Rico, and the Virgin Islands, in one 
gigantic island. The passage between Cuba and Jamaica has a 
depth of 3,000 fathoms, and that between Hayti and Cuba is 
not less than 873 fathoms, the latter being probably an arm of 
the Atlantic. The 500-fathom line connects, as a gigantic 
island, the banks uniting Anguilla to St. Bartholomew, Saba 
Bank, the one connecting St. Eustatius to Nevis, Barbuda to 
Antigua, and from thence extends south so as to include Guade- 
loupe, Marie Galante, and Dominica. This 500-fathom line 
thus forms one gigantic island of the northern islands, extend- 
ing from Saba Bank to Santa Cruz, and leaving but a narrow 
channel between it and the eastern end of the 500-fathom line 
running round Santa Cruz. As Santa Cruz is separated from 
St. Thomas by a channel of 40 miles, with a maximum depth of 
over 2,400 fathoms, this plainly shows its connection with the 
northern islands of the Caribbean group rather than with St. 
Thomas, as is also well shown by the geographical relations of its 
mollusca. The 500-fathom line again unites, in one gigantic 
spit, extending northerly from the mouth of the Orinoco, all the 
islands to the south of Martinique, leaving Barbadoes to the 
east, and a narrow passage between Martinique and the islands 
of Dominica and St. Lucia. At the time of this connection, 
therefore, the Caribbean Sea was connected with the Atlantic only 
by a narrow passage of a few miles in width between St. Lucia 
and Martinique, and one somewhat wider and slightly deeper 
between Martinique and Dominica, another between Sombrero 
and the Virgin Islands, and a comparatively narrow passage be- 
tween Jamaica and Hayti. The Caribbean Sea, therefore, must have 
been a gulf of the Pacific, or have been connected with it through 
wide passages, of which we find the traces in the Tertiary and 
Cretaceous deposits of the Isthmus of Darien, of Panama, and of 
Nicaragua. Central America and northern South America at 
that time must have been a series of large islands with passages 
between them from the Pacific into the Caribbean. It is further 
interesting to speculate what must have become of the great 
equatorial current produced by the north-east trades. The water 
banking up against the two large islands then forming the 
Caribbean Islands must, of course, have been deflected north, 
have swept round the northern shores of the Virgin Islands, 
Porto Rico, and Hayti, and poured into the western basin 
! 
