The Notebooks of Leonardo Da Vinci

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Page 990 of 1565.
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That in the drifts, among one and another, there are still to be
found the traces of the worms which crawled upon them when they were
not yet dry. And all marine clays still contain shells, and the
shells are petrified together with the clay. From their firmness and
unity some persons will have it that these animals were carried up
to places remote from the sea by the deluge. Another sect of
ignorant persons declare that Nature or Heaven created them in these
places by celestial influences, as if in these places we did not
also find the bones of fishes which have taken a long time to grow;
and as if, we could not count, in the shells of cockles and snails,
the years and months of their life, as we do in the horns of bulls
and oxen, and in the branches of plants that have never been cut in
any part. Besides, having proved by these signs the length of their
lives, it is evident, and it must be admitted, that these animals
could not live without moving to fetch their food; and we find in
them no instrument for penetrating the earth or the rock where we
find them enclosed. But how could we find in a large snail shell the
fragments and portions of many other sorts of shells, of various
sorts, if they had not been thrown there, when dead, by the waves of
the sea like the other light objects which it throws on the earth?
Why do we find so many fragments and whole shells between layer and
layer of stone, if this had not formerly been covered on the shore
by a layer of earth thrown up by the sea, and which was afterwards
petrified? And if the deluge before mentioned had carried them to
these parts of the sea, you might find these shells at the boundary
of one drift but not at the boundary between many drifts. We must
also account for the winters of the years during which the sea
multiplied the drifts of sand and mud brought down by the
neighbouring rivers, by washing down the shores; and if you chose to
say that there were several deluges to produce these rifts and the
shells among them, you would also have to affirm that such a deluge
took place every year. Again, among the fragments of these shells,
it must be presumed that in those places there were sea coasts,
where all the shells were thrown up, broken, and divided, and never
in pairs, since they are found alive in the sea, with two valves,
each serving as a lid to the other; and in the drifts of rivers and
on the shores of the sea they are found in fragments. And within the
limits of the separate strata of rocks they are found, few in number
and in pairs like those which were left by the sea, buried alive in
the mud, which subsequently dried up and, in time, was petrified.

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