Now I could not account for
this difference except by supposing that the roughened fragments were
the only ones which had been _completely absorbed_--that the others
had entered the whirl at so late a period of the tide, or, from some
reason, had descended so slowly after entering, that they did not
reach the bottom before the turn of the flood came, or of the ebb, as
the case might be. I conceived it possible, in either instance, that
they might thus be whirled up again to the level of the ocean, without
undergoing the fate of those which had been drawn in more early or
absorbed more rapidly. I made, also, three important observations. The
first was, that as a general rule, the larger the bodies were, the
more rapid their descent; the second, that, between two masses of
equal extent, the one spherical, and the other _of any other shape,_
the superiority in speed of descent was with the sphere; the third,
that, between two masses of equal size, the one cylindrical, and the
other of any other shape, the cylinder was absorbed the more slowly.
Since my escape, I have had several conversations on this subject with
an old schoolmaster of the district; and it was from him that I
learned the use of the words 'cylinder' and 'sphere.' He explained to
me--although I have forgotten the explanation--how what I observed
was, in fact, the natural consequence of the forms of the floating
fragments, and showed me how it happened that a cylinder, swimming in
a vortex, offered more resistance to its suction, and was drawn in
with greater difficulty, than an equally bulky body, of any form
whatever.
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