scovering, in the territory of Parma (what Spada had observed near
Verona, and Schiavo in Sicily), that fossil shells were not scattered
through the rocks at random, but disposed in regular order, according to
certain genera and species.

_Vitaliano Donati_, 1750.--But with a view of throwing further light
upon these questions, Donati, in 1750, undertook a more extensive
investigation of the Adriatic, and discovered, by numerous soundings,
that deposits of sand, marl, and tufaceous incrustations, most strictly
analogous to those of the Subapennine hills, were in the act of
accumulating there. He ascertained that there were no shells in some of
the submarine tracts, while in other places they lived together in
families, particularly the genera Arca, Pecten, Venus, Murex, and some
others. He also states that in divers localities he found a mass
composed of corals, shells, and crustaceous bodies of different species,
confusedly blended with earth, sand, and gravel. At the depth of a foot
or more, the organic substances were entirely petrified and reduced to
marble; at less than a foot from the surface, they approached nearer to
their natural state; while at the surface they were alive, or, if dead,
in a good state of preservation.

_Baldassari_.--A contemporary naturalist, Baldassari, had shown that the
organic remains in the tertiary marls of the Siennese territory were
grouped in families, in a manner precisely similar to that above alluded
to by Donati.

_Buffon_, 1749.--Buffon first made known his theoretical views
concerning the former changes of the earth, in his Natural History,
published in 1749. He adopted the theory of an original volcanic
nucleus, together with the universal ocean of Leibnitz. By this aqueous
envelope the highest mountains were once covered. Marine currents then
acted violently, and formed horizontal strata, by washing away solid
matter in some parts, and depositing it in others; they also excavated
deep submarine valleys. The level of the ocean was then depressed by the
entrance of a part of its waters into subterranean caverns, and thus
some land was left dry. Buffon seems not to have profited, like Leibnitz
and Moro, by the observations of Steno, or he could not have imagined
that the strata were generally horizontal, and that those which contain
organic remains had never been disturbed since the era of their
formation. He was conscious of the great power annually exerted by
rivers and mar