The Rise and Progress of Palaeontology | Page 5

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 palaeontology, stated
generally, is this: "Given a body endowed with a certain shape and
produced in accordance with natural laws, to find in that body itself the
evidence of the place and manner of its production."<1> The only way
of solving this problem is by the application of the axiom that "like
effects imply like causes," or as Steno puts it, in reference to this
particular case, that "bodies which are altogether similar have been
produced in the same way."<2> Hence, since the glossopetrae are
altogether similar to sharks' teeth, they must have been produced by
sharklike fishes; and since many fossil shells correspond, down to the
minutest details of structure, with the shells of existing marine or
freshwater animals, they must have been produced by similar animals;
and the like reasoning is applied by Steno to the fossil bones of
vertebrated animals, whether aquatic or terrestrial. To the obvious
objection that many fossils are not altogether similar to their living
analogues, differing in substance while agreeing in form, or being mere
hollows or impressions, the surfaces of which are figured in the same
way as those of animal or vegetable organisms, Steno replies by
pointing out the changes which take place in organic remains
embedded in the earth, and how their solid substance may be dissolved
away entirely, or replaced by mineral matter, until nothing is left of the
original but a cast, an impression, or a mere trace of its contours. The
principles of investigation thus excellently stated and illustrated by
Steno in 1669, are those which have, consciously or unconsciously,
guided the researches of palaeontologists ever since. Even that feat of
palaeontology which has so powerfully impressed the popular

imagination, the reconstruction of an extinct animal from a tooth or a
bone, is based upon the simplest imaginable application of the logic of
Steno. A moment's consideration will show, in fact, that Steno's
conclusion that the glossopetrae are sharks' teeth implies the
reconstruction of an animal from its tooth. It is equivalent to the
assertion that the animal of which the glossopetrae are relics had the
form and organisation of a shark; that it had a skull, a vertebral column,
and limbs similar to those which are characteristic of this group of
fishes; that its heart, gills, and intestines presented the peculiarities
which those of all sharks exhibit; nay, even that any hard parts which
its integument contained were of a totally different character from the
scales of ordinary fishes. These conclusions are as certain as any based
upon probable reasonings can be. And they are so, simply because a
very large experience justifies us in believing that teeth of this
particular form and structure are invariably associated with the peculiar