62 THREE CRUISES OF THE “ BLAKE.” 
of this folding, the formation of an immense submarine plateau, 
directly in the track of the Gulf Stream, by the accretions of 
the solid parts of mollusks, echinoderms, corals, haleyonoids, 
annelids, crustacea, and the like, which have lived and died 
upon it; these solid parts have furnished the limestone for the 
gradual completion of the peninsula. No one who has not 
dredged near the hundred-fathom line on the west coast of 
the great Florida plateau can form any idea of the amount of 
animal life which can be sustained upon a small area under 
suitable conditions of existence. It was no uncommon thing 
for us to bring up in the trawl or dredge large fragments of 
the modern limestone now in process of formation, consisting 
of the dead carcasses of the very species now living on the 
top of this recent limestone. To the westward of the western 
shore line, Florida now stretches out as an immense submarine 
plateau, forming, as the sections show, a huge tongue coated or 
veneered only by coral limestone over its very top. The whole 
of the peninsula of Florida south of St. Augustine, as far as 
Tampa Bay, has probably in this way been built up from north 
to south, of limestone somewhat older than the reef limestone. 
The plateau, judging from the inclination of the axis, has but a 
slight southward dip until one reaches the southern extremity of 
the peninsula, where the fall is more rapid toward the outer reef. 
The whole of the eastern and western edges of Florida con- 
sist of recent limestones, the immediate predecessors of that 
which is now forming on the western and southern slopes of 
the great Florida plateau. The early dredgings of Mr. Pour- 
talés, in 1867 and 1868, developed on the Gulf Stream slope 
off the Florida reefs an extensive rocky plateau (Pourtalés 
Plateau) from a depth of about ninety fathoms to about two 
hundred and fifty fathoms. The rock of which this plateau is 
built (see Fig. 192) consists of the same species of corals and 
shells as those now living upon it, to which it owes its forma- 
tion. A similar sea-bottom is found on the north side of Cuba, 
1 Mr. S. P. Sharples, who examined of lime, the balance being organie matter 
specimens of rock from the Pourtalés and phosphate of lime. 
Plateau, found the eorals made up of The recent limestone found on the 
about ninety-five per cent. of carbonate Pourtalés Plateau contained from thirty- 
