c substance, might, in the absence of such knowledge, be
fairly interpreted as the expression of a process of development in the
opposite direction--from the mineral to the organic. Moreover, in an age
when it would have seemed the most absurd of paradoxes to suggest that
the general level of the sea is constant, while that of the solid land
fluctuates up and down through thousands of feet in a secular ground
swell, it may well have appeared far less hazardous to conceive that
fossils are sports of nature than to accept the necessary alternative,
that all the inland regions and highlands, in the rocks of which marine
shells had been found, had once been covered by the ocean. It is not so
surprising, therefore, as it may at first seem, that although such men
as Leonardo da Vinci and Bernard Palissy took just views of the nature
of fossils, the opinion of the majority of their contemporaries set
strongly the other way; nor even that error maintained itself long after
the scientific grounds of the true interpretation of fossils had been
stated, in a manner that left nothing to be desired, in the latter half
of the seventeenth century. The person who rendered this good service
to palaeontology was Nicolas Steno, professor of anatomy in Florence,
though a Dane by birth. Collectors of fossils at that day were familiar
with certain bodies termed "glossopetrae," and speculation was rife as
to their nature. In the first half of the seventeenth century, Fabio
Colonna had tried to convince his colleagues of the famous Accademia dei
Lincei that the glossopetrae were merely fossil sharks' teeth, but his
arguments made no impression. Fifty years later, Steno re-opened the
question, and, by dissecting the head of a shark and pointing out the
very exact correspondence of its teeth with the glossopetrae, left no
rational doubt as to the origin of the latter. Thus far, the work of
Steno went little further than that of Colonna, but it fortunately
occurred to him to think out the whole subject of the interpretation of
fossils, and the result of his meditations was the publication, in 1669,
of a little treatise with the very quaint title of "De Solido intra
Solidum naturaliter contento." The general course of Steno's argument
may be stated in a few words. Fossils are solid bodies which, by some
natural process, have come to be contained within other solid bodies,
namely, the rocks in which they are embedded; and the fundamental
problem of pa