As to the bottom of the basin of the sea, it seems to have inequalities
similar to those which the surface of continents exhibits; if it were
dried up, it would present mountains, valleys, and plains. It is
inhabited almost throughout its whole extent by an immense quantity of
testaceous animals, or covered with sand and gravel. It was thus that
Donati found the bottom of the Adriatic sea; the bed of testaceous
animals there, according to him, is several hundred feet in thickness.
The celebrated diver Pescecola, whom the emperor Frederick II. employed
to descend the strait of Messina, saw there with horror, enormous polypi
attached to the rocks, the arms of which, being several yards long, were
more than sufficient to strangle a man. In a great many places, the
madrepores form a kind of petrified forest fixed at the bottom of the
sea, and frequently, too, this bottom plainly presents different layers
of rock and earth.
The granite rises up in sharp-pointed masses. Near Marseilles, marble is
dug up from a submarine quarry. There are also bituminous springs, and
even springs of fresh water, that spout up from the depths of the ocean;
and in the Gulf of Spezia, a great spout or fountain of fresh water is
seen to rise like a liquid hill. Similar springs furnish the inhabitants
of the town of Aradus with their ordinary beverage.
On the southern coast of Cuba, to the southwest of the port of Batabano,
in the bay of Xagua, at two or three miles from the land, springs of
fresh water gush up with such force in the midst of the salt, that small
boats cannot approach them with safety; the deeper you draw the water,
the fresher you find it. It has been observed, that in the neighbourhood
of steep coasts, the bottom of the sea also sinks down suddenly to a
considerable depth; whilst near a low coast, and one of gentle
declivity, it is only gradually that the sea deepens. There are some
places in the sea where no bottom has yet been found. But we must not
conclude that the sea is really bottomless; an idea, which, if not
absurd, is, at least, by no means conformable to the analogies of
natural science. The mountains of continents seem to correspond with
what are called the abysses of the sea; but now, the highest mountains
do not rise to 20,000 feet. It is true that they have wasted down and
lessened by the action of the elements; it may, therefore, be reasonably
concluded, that the sea is not beyond 30,000 feet in depth; but it is
impossible to find the bottom even at one-third of this depth, with our
little instruments. The greatest depth that has been tried to be
measured, is that found in the northern ocean by Lord Mulgrave; he
heaved a very heavy sounding lead, and gave out with it cable rope to
the length of 4,680 feet, without finding bottom.--_Blake's
Encyclopedia_.
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