there was a tilting of this broad tract of the earth’s
crust, which lifted the side now occupied by the
Cordilleras and sank the region of the Antilles to a
level even lower than that of the present time.
Then the plains, which may have had lakes in their
central depressions, were converted into the basins
of the Caribbean Sea and the Gulf of Mexico, the
plateaus became the higher levels of the ocean floor,
while the valleys between them, and the cafions
and ravines by which they were cleft, were chasms
in the great deep, and only the mountain ridges and
peaks were left above the expanse of waters as
islands of varying form and extent. There is geological
evidence that after the great subsidence there
was a gradual lifting, at least of a part of this tract,
toward the older level.
T h e plateau upon whose elevations and projections
the Bahamas are built is a continuation of the North
American continent, and stretches from Florida eastward
about three hundred miles, with a level nowhere
more than 3500 feet below the water surface
until it reaches the outer edge, where a steep escarpment
dips abruptly to the ocean depths of 12,000
feet and more. Upon this are banks and ridges
and mounds, some of which come to the surface as
islands, or near enough for the polyps to build their
coral structures to the sunlight and make isles and
reefs and calcareous rocks; and here and there the
plateau is seamed with valleys, some of which are
old extensions of river beds of the continent, and is
cut by deep fiords which were formed when the
whole region was above the water-level. T h e high,-.
lest culmination now is about three hundred and
eighty feet on Cat Island.
I The plateau of the Bahamas slopes off to the
Louth into the Old Bahama Channel near the eastern
end of Cuba to a depth of 6000 feet, and to more
‘than 5000 north of the western part of the great
¡island. The Florida Straits have scarcely a third of
this depth, but they deepen and widen into the Gulf
of Mexico, whose basin is some 12,000 feet in depth
near the middle. T h e Yucatan Channel is about
¡60 0 0 feet deep off the western end of Cuba, but rises
to higher levels toward the opposite peninsula, while
the western section of the Caribbean Sea, sometimes
ta ile d the Sea of Honduras, sinks to vast depths.
T he re is a submarine ridge extending west from
iCape Cruz on the south coast of Cuba which comes
to the surface in the Cayman Islands. South of this
is a pit in the bottom of the sea, 20,000 feet deep,
measured from the surface of the water. Another
broad ridge extends from Cape Tiburon, Haiti,
through Jamaica and on toward Cape Gracias k Dios
at the angle of Central America, where Honduras
and Nicaragua meet, and from that ridge the bottom
¡¡slopes gradually to the south-east into the Caribbean
depths of 15,000 feet. T h e deepest place in all these
Iwaters, one of the deepest in all the vast ocean, is
directly north of Puerto Rico, where soundings have
gone down more than 27,000 feet.
When this region was at its highest elevation the
iBahama plateau connected with the North Ameri-
■qan continent and the Greater Antilles, and the e x panse
of land continued to Mexico and Central