ish best in water will spring up
and grow upon these islands. Peat, too, in bogs, will float and form
islands, for the simple reason that it is of less specific gravity than
water; and vegetation will also spring up on these peat islands. But
all this furnishes no evidence that the invariable law of nature, which
carries to the bottom the heaviest body, has been suspended at Mexico.
Had the floating gardens been built in large boats made water-tight,
they might have floated. But, unfortunately, the Indians had not the
means for constructing such boats. Even timber-rafts would have become
saturated in time, and sunk, as rafts of logs do if kept too long in
the "mill-pond," waiting to be sawed into lumber.

There is another law of nature, which must not be lost sight of, which
is at war with the idea of a garden floating on a bed of rushes; and
that is capillary attraction, which would raise particles of water, one
by one, among the fibres of the rushes until the frail raft on which
the earth rested was saturated; and still pressing upward, the busy
drops would penetrate the superincumbent earth, moistening and adding
to the specific gravity of the garden by filling the porous earth until
it became too heavy to float, if it ever had floated.

Nearly three hundred years had passed away before men ventured to
question the truth of the statement that the gardens along the canal of
Chalco ever floated, and then it seemed like temerity to raise the
question, even if it were only a popular fallacy. It has therefore been
treated by all modern writers as a well-established matter, and one of
not sufficient importance to justify its minute investigation. With me
the question was a far different one. I had, after careful inquiry and
observation, come to the conclusion that the marshes of the valley of
Mexico were, in the time of Cortez, substantially in the condition in
which we find them at the present day; that the filling up they had
undergone in that time was counterbalanced by the relief they had
gained by the canal of Huehuetoca. The chinampas constitute an
important link in the chain of proofs to establish this fact. If I have
succeeded in showing that these gardens of the Aztecs, instead of
floating upon the water, rested upon the muddy bottom, it follows as a
matter of course that the depth of the water in the laguna could not,
in the day of the Aztecs, have been materially greater than it now is.

[35] _Essai Poli