Of the bones of fish that are found in petrified fish. All the animals that have their bones inside their skin, and that have been covered by the muds of the river floods far from the ordinary beds of those rivers, have been minutely imprinted by such muds. And in time, the beds of the rivers having been lowered, such animals, imprinted and enclosed in that mud and having consumed their fleshiness and intestines so that only the bones remain, out of their natural order, have fallen to the bottom of the cavity of their imprint. In that cavity, when the mud, by its raising up out of the river's course, has dried of its watery moisture, it takes on the viscous moisture and becomes stone, enclosing whatever is found within it; and filling every void of itself, and finding the cavity of the imprint of such animals, it penetrates there subtly through the minute pores of the earth. Through those pores the air that occupied within escapes by the lateral parts, because above it cannot escape, since that porosity is occupied by the humour which descends into the void, and below it cannot escape, because the humour already fallen has closed off the porosity below. The lateral parts remain open, whence that air, condensed and pressed by the descending humour, escapes with the same slowness as the humour that descends there. And so, dried, that humour becomes stone without graininess, and preserves the same form of the animal that imprinted itself there, and inside it the bones remain.