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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。〃 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。〃 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 organisation of sharks； and are
never found in connection with other organisms。 Why this should
be we are not at present in a position even to imagine； we must
take the fact as an empirical law of animal morphology； the
reason of which may possibly be one day found in the history of
the evolution of the shark tribe； but for which it is hopeless
to seek for an explanation in ordinary physiological reasonings。
Every one practically acquainted with palaeontology is aware
that it is not every tooth； nor every bone； which enables us to
form a judgment of the character of the animal to which it
belonged； and that it is possible to possess many teeth； and
even a large portion of the skeleton of an extinct animal； and
yet be unable to reconstruct its skull or its limbs。 It is only
when the tooth or bone presents peculiarities； which we know by
previous experience to be characteristic of a certain group；
that we can safely predict that the fossil belonged to an animal
of the same group。 Any one who finds a cow's grinder may be
perfectly sure that it belonged to an animal which had two
complete toes on each foot and ruminated； any one who finds a
horse's grinder may be as sure that it had one complete toe on
each foot and did not ruminate； but if ruminants and horses were
extinct animals of which nothing but the grinders had ever been
discovered； no amount of physiological reasoning could have
enabled us to reconstruct either animal； still less to have
divined the wide differences between the two。 Cuvier； in the
〃Discours sur les Revolutions de la Surface du Globe；〃 strangely
credits himself； and has ever since been credited by others；
with the invention of a new method of palaeontological research。
But if you will turn to the 〃Recherches sur les Ossemens
Fossiles〃 and watch Cuvier； not speculating； but working； you
will find that his method is neither more nor less than that of
Steno。 If he was able to make his famous prophecy from the jaw
which lay upon the surface of a block of stone to the pelvis of
the same animal which lay hidden in it； it was not because
either he； or any one else； knew； or knows； why a certain form
of jaw is； as a rule； constantly accompanied by the presence of
marsupial bones； but simply because experience has shown that
these two structures are co…ordinated。
The settlement of the nature of fossils led at once to the next
advance of palaeontology； viz。 its application to the
deciphering of the history of the earth。 When it was admitted
that fossils are remains of animals and plants； it followed
that； in so far as they resemble terrestrial； or freshwater；
animals and plants； they are evidences of the existence of land；
or fresh water； and； in so far as they resemble marine
organisms； they are evidences of the existence of the sea at the
time at which they were parts of actually living animals and
plants。 Moreover； in the absence of evidence to the contrary； it
must be admitted that the terrestrial or the marine organisms
implied the existence of land or sea at the place in which they
were found while they were yet living。 In fact； such conclusions
were immediately drawn by everybody； from the time of Xenophanes
downwards； who believed that fossils were really organic
remains。 Steno discusses their value as evidence of repeated
alteration of marine and terrestrial conditions upon the soil of
Tuscany in a manner worthy of a modern geologist。
The speculations of De Maillet in the beginning of the
eighteenth century turn upon fossils； and Buffon follows him
very closely in those two remarkable works； the 〃Theorie de la
Terre〃 and the 〃Epoques de la Nature〃 with which he commenced
and ended his career as a naturalist。
The opening sentences of the 〃Epoques de la Nature〃 show us how
fully Buffon recognised the analogy of geological with
archaeological inquiries。 〃As in civil history we consult deeds；
seek for coins； or decipher antique inscriptions in order to
determine the epochs of human revolutions and fix the date of
moral events； so； in natural history； we must search the
archives of the world； recover old monuments from the bowels of
the earth； collect their fragmentary remains； and gather into
one body of evidence all the signs of physical change which may
enable us to look back upon the different ages of nature。 It is
our only means of fixing some points in the immensity of space；
and of setting a certain number of waymarks along the eternal
path of time。〃
Buffon enumerates five classes of these monuments of the past
history of the earth； and they are all facts of palaeontology。
In the first place； he says； shells and other marine productions
are found all over the surface and in the interior of the dry
land； and all calcareous rocks are made up of their remains。
Secondly； a great many of these shells which are found in Europe
are not now to be met with in the adjacent seas； and； in the
slates and other deep…seated deposits； there are remains of
fishes and of plants of which no species now exist in our
latitudes； and which are either extinct； or exist only in more
northern climates。 Thirdly； in Siberia and in other northern
regions of Europe and of Asia； bones and teeth of elephants；
rhinoceroses； and hippopotamuses occur in such numbers that
these animals must once have lived and multiplied in those
regions； although at the present day they are confined to
southern climates。 The deposits in which these remains are found
are superficial； while those which contain shells and other
marine remains lie much deeper。 Fourthly； tusks and bones of
elephants and hippopotamuses are found not only in the northern
regions of the old world； but also in those of the new world；
although； at present； neither elephants nor hippopotamuses occur
in America。 Fifthly； in the midd