The name of _Fossil_ (from _fossilis_, dug up) is given to all organised
bodies, animal or vegetable, buried naturally in the terrestrial strata,
and more or less petrified, that is, converted into stone. Fossils of
the older formations are remains of organisms which, so far as species
is concerned, are quite extinct; and only those of recent formations
belong to genera living in our days. These fossil remains have neither
the beauty nor the elegance of most living species, being mutilated,
discoloured, and often almost shapeless; they are, therefore,
interesting only in the eyes of the observer who would interrogate them,
and who seeks to reconstruct, with their assistance, the Fauna and Flora
of past ages. Nevertheless, the light they throw upon the past history
of the earth is of the most satisfactory description, and the science of
fossils, or palæontology, is now an important branch of geological
inquiry. Fossil shells, in the more recent deposits, are found scarcely
altered; in some cases only an impression of the external form is
left--sometimes an entire cast of the shell, exterior and interior. In
other cases the shell has left a perfect impression of its form in the
surrounding mud, and has then been dissolved and washed away, leaving
only its mould. This mould, again, has sometimes been filled up by
calcareous spar, silica, or pyrites, and an exact cast of the original
shell has thus been obtained. Petrified wood is also of very common
occurrence.
These remains of an earlier creation had long been known to the curious,
and classed as _freaks of Nature_, for so we find them described in the
works of the ancient philosophers who wrote on natural history, and in
the few treatises on the subject which the Middle Ages have bequeathed
to us. Fossil bones, especially those of elephants, were known to the
ancients, giving rise to all sorts of legends and fabulous histories:
the tradition which attributed to Achilles, to Ajax, and to other heroes
of the Trojan war, a height of twenty feet, is attributable, no doubt,
to the discovery of the bones of elephants near their tombs. In the time
of Pericles we are assured that in the tomb of Ajax a _patella_, or
knee-bone of that hero, was found, which was as large as a dinner-plate.
This was probably only the patella of a fossil elephant.
The uses to which fossils are applied by the geologist are--First, to
ascertain the relative age of the formations in which they occur;
secondly, the conditions under which these were deposited. The age of
the formation is determined by a comparison of the fossils it contains
with others of ascertained date; the conditions under which the rocks
were deposited, whether marine, lacustrine, or terrestrial, are readily
inferred from the nature of the fossils. The great artist, Leonardo da
Vinci, was the first to comprehend the real meaning of fossils, and
Bernard Palissy had the glory of being the first modern writer to
proclaim the true character of the fossilised remains which are met
with, in such numbers, in certain formations, both in France and Italy,
particularly in those of Touraine, where they had come more especially
under his notice. In his work on “Waters and Fountains,” published in
1580, he maintains that the _figured stones_, as fossils were then
called, were the remains of organised beings preserved at the bottom of
the sea. But the existence of marine shells upon the summits of
mountains had already arrested the attention of ancient authors. Witness
Ovid, who in Book XV. of the “Metamorphoses” tells us he had seen land
formed at the expense of the sea, and marine shells lying dead far from
the ocean; and more than that, an ancient anchor had been found on the
very summit of a mountain.
“Vidi factas ex æquore terras,
Et procul a pelago conchæ jacuere marinæ,
Et vetus inventa est in montibus anchora summis.”
Ov., _Met._, Book xv.
The Danish geologist Steno, who published his principal works in Italy
about the middle of the seventeenth century, had deeply studied the
fossil shells discovered in that country. The Italian painter Scilla
produced in 1670 a Latin treatise on the fossils of Calabria, in which
he established the organic nature of fossil shells.
The eighteenth century gave birth to two very opposite theories as to
the origin of our globe--namely, the _Plutonian_ or igneous, and the
_Neptunian_ or aqueous theory. The Italian geologists gave a marked
impulse to the study of fossils, and the name of Vallisneri[1] may be
cited as the author to whom science is indebted for the earliest account
of the marine deposits of Italy, and of the most characteristic organic
remains which they contain. Lazzaro Moro[2] continued the studies of
Vallisneri, and the monk Gemerelli reduced to a complete system the
ideas of these two geologists, endeavouring to explain all the phenomena
as Vallisneri had wished, “without violence, without fiction, without
miracles.” Marselli and Donati both studied in a very scientific manner
the fossil shells of Italy, and in particular those of the Adriatic,
recognising the fact that they affected in their beds a regular and
constant order of superposition.[3]
[1] Dei corpi marini, &c., 1721.
[2] Sui crostaccei ed altri corpi marini che sè trovano sui monti,
1740.
[3] Consult Lyell’s “Principles of Geology” and the sixth edition of
the “Elements,” with much new matter, for further information
relative to the study of fossils during the last two centuries.
In France the celebrated Buffon gave, by his eloquent writings, great
popularity to the notions of the Italian naturalists concerning the
origin of fossil remains. In his admirable “Époques de la Nature” he
sought to prove that the shells found in great quantities buried in the
soil, and even on the tops of mountains, belonged, in reality, to
species not living in our days. But this idea was too novel not to find
objectors: it counted among its adversaries the bold philosopher who
might have been expected to adopt it with most ardour. Voltaire
attacked, with his jesting and biting criticism, the doctrines of the
illustrious innovator. Buffon insisted, reasonably enough, that the
presence of shells on the summit of the Alps was a proof that the sea
had at one time occupied that position. But Voltaire asserted that the
shells found on the Alps and Apennines had been thrown there by pilgrims
returning from Rome. Buffon might have replied to his opponent, by
pointing out whole mountains formed by the accumulation of these shells.
He might have sent him to the Pyrenees, where shells of marine origin
cover immense areas to a height of 6,600 feet above the present
sea-level. But his genius was averse to controversy; and the philosopher
of Ferney himself put an end to a discussion in which, perhaps, he would
not have had the best of the argument. “I have no wish,” he wrote, “to
embroil myself with Monsieur Buffon about shells.”
It was reserved for the genius of George Cuvier to draw from the study
of fossils the most wonderful results: it is the study of these remains,
in short, which, in conjunction with mineralogy, constitutes in these
days positive geology. “It is to fossils,” says the great Cuvier, “that
we owe the discovery of the true theory of the earth; without them we
should not have dreamed, perhaps, that the globe was formed at
successive epochs, and by a series of different operations. They alone,
in short, tell us with certainty that the globe has not always had the
same envelope; we cannot resist the conviction that they must have lived
on the surface of the earth before being buried in its depths. It is
only by analogy that we have extended to the primary formations the
direct conclusions which fossils furnish us with in respect to the
secondary formations; and if we had only unfossiliferous rocks to
examine, no one could maintain that the earth was not formed all at
once.”[4]
[4] “Ossements Fossiles” (4to), vol. i., p. 29.
The method adopted by Cuvier for the reconstruction and restoration of
the fossil animals found in the plaster-quarries of Montmartre, at the
gates of Paris, has served as a model for all succeeding naturalists;
let us listen, then, to his exposition of the vast problem whose
solution he proposed to himself. “In my work on fossil bones,” he says,
“I propose to ascertain to what animals the osseous fragments belong; it
is seeking to traverse a road on which we have as yet only ventured a
few steps. An antiquary of a new kind, it seemed to me necessary to
learn both to restore these monuments of past revolutions, and to
decipher their meaning. I had to gather and bring together in their
primitive order the fragments of which they are composed; to reconstruct
the ancient beings to which these fragments belonged; to reproduce them
in their proportions and with their characteristics; to compare them,
finally, with others now living on the surface of the globe: an art at
present little known, and which supposes a science scarcely touched upon
as yet, namely, that of the laws which preside over the co-existence of
the forms of the several parts in organised beings. I must, then,
prepare myself for these researches by others, still more extended, upon
existing animals. A general review of actual creation could alone give a
character of demonstration to my account of these ancient inhabitants
of the world; but it ought, at the same time, to give me a great
collection of laws, and of relations not less demonstrable, thus forming
a body of new laws to which the whole animal kingdom could not fail to
find itself subject.”[5]
[5] “Ossements Fossiles” (4to), vol. i., pp. 1, 2.
“When the sight of a few bones inspired me, more than twenty years ago,
with the idea of applying the general laws of comparative anatomy to the
reconstruction and determination of fossil species; when I began to
perceive that these species were not quite perfectly represented by
those of our days, which resembled them the most--I no longer doubted
that I trod upon a soil filled with spoils more extraordinary than any I
had yet seen, and that I was destined to bring to light entire races
unknown to the present world, and which had been buried for incalculable
ages at great depths in the earth.
“I had not yet given any attention to the published notices of these
bones, by naturalists who made no pretension to the recognition of their
species. To M. Vaurin, however, I owe the first intimation of the
existence of these bones, with which the gypsum-quarries swarm. Some
specimens which he brought me one day struck me with astonishment; I
learned, with all the interest the discovery could inspire me with, that
this industrious and zealous collector had already furnished some of
them to other collectors. Received by these amateurs with politeness, I
found in their collections much to confirm my hopes and heighten my
curiosity. From that time I searched in all the quarries with great care
for other bones, offering such rewards to the workmen as might awaken
their attention. I soon got together more than had ever been previously
collected, and after a few years I had nothing to desire in the shape of
materials. But it was otherwise with their arrangement, and with the
reconstruction of the skeleton, which could alone lead to any just idea
of the species.
“From the first moment of discovery I perceived that, in these remains,
the species were numerous. Soon afterwards I saw that they belonged to
many genera, and that the species of the different genera were nearly
the same size, so that size was likely rather to hinder than aid me.
Mine was the case of a man to whom had been given at random the
mutilated and imperfect remains of some hundreds of skeletons belonging
to twenty sorts of animals; it was necessary that each bone should find
itself alongside that to which it ought to be connected: it was almost
like a small resurrection, and I had not at my disposal the
all-powerful trumpet; but I had the immutable laws prescribed to living
beings as my guide; and at the voice of the anatomist each bone and each
part of a bone took its place. I have not expressions with which to
describe the pleasure I experienced in finding that, as soon as I
discovered the character of a bone, all the consequences of the
character, more or less foreseen, developed themselves in succession:
the feet were found conformable to what the teeth announced; the teeth
to that announced by the feet; the bones of the legs, of the thighs, all
those which ought to reunite these two extreme parts, were found to
agree as I expected; in a word, each species was reproduced, so to
speak, from only one of its elements.”[6]
[6] “Ossements Fossiles,” vol. iv. (4to), p. 32.
While the Baron Cuvier was thus zealously prosecuting his inquiries in
France, assisted by many eminent fellow-labourers, what was the state of
geological science in the British Islands? About that same time, Dr.
William Smith, better known as “the father of English geology,” was
preparing, unaided, the first geological map of this country. Dr. Smith
was a native of Wiltshire, and a canal engineer in Somersetshire; his
pursuits, therefore, brought him in the midst of these hieroglyphics of
Nature. It was his practice, when travelling professionally, during many
years to consult masons, miners, wagoners, and agriculturists. He
examined the soil; and in the course of his inquiries he came to the
conclusion that the earth was not all of the same age; that the rocks
were arranged in layers, or strata, superimposed on each other in a
certain definite order, and that the strata, when of the same age, could
be identified by means of their organic remains. In 1794 he formed the
plan of his geological map, showing the superposition of the various
beds; for a quarter of a century did he pursue his self-allotted task,
which was at last completed, and in 1801 was published, being the first
attempt to construct a stratigraphical map.
Taking the men in the order of the objects of their investigation,
rather than in chronological order, brings before us the patient and
sagacious investigator to whom we are indebted for our knowledge of the
Silurian system. For many years a vast assemblage of broken and
contorted beds had been observed on the borders of North Wales,
stretching away to the east as far as Worcestershire, and to the south
into Gloucester, now rising into mountains, now sinking into valleys.
The ablest geologists considered them as a mere labyrinth of ruins,
whose order of succession and distinctive organic remains were entirely
unknown, “But a man came,” as M. Esquiros eloquently writes, “who threw
light upon this sublime confusion of elements.” Sir Roderick Impey
Murchison, then a young President of the Geological Society, had his
attention directed, as he himself informs us, to some of these beds on
the banks of the Wye. After seven years of unremitting labour, he was
rewarded by success. He established the fact that these sedimentary
rocks, penetrated here and there by eruptive masses of igneous origin,
formed a unique system, to which he gave the name of _Silurian_, because
the rocks which he considered the most typical of the whole were most
fully developed, charged with peculiar organic remains, in the land of
the ancient Silures, who so bravely opposed the Roman invaders of their
country. Many investigators have followed in Sir Roderick’s steps, but
few men have so nobly earned the honours and fame with which his name is
associated.
The success which attended Sir R. Murchison’s investigations soon
attracted the attention of other geologists. Professor Sedgwick examined
the older slaty strata, and succeeded in proving the position of the
Cambrian rocks to be at the base of the Silurian. Still it was reserved
for Sir William Logan, the Director of the Canadian Geological Survey,
to establish the fact that immense masses of gneissic formation lay at
the base of the Cambrian; and, by subsequent investigations, Sir
Roderick Murchison satisfied himself that this formation was not
confined to Canada, but was identical with the rocks termed by him
Fundamental Gneiss, which exist in enormous masses on the west coast of
Scotland, and which he proved to be the oldest stratified rocks in the
British Isles. Subsequently he demonstrated the existence of these same
Laurentian rocks in Bohemia and Bavaria, far beneath the Silurian rocks
of Barrande.
While Murchison and Sedgwick were prosecuting their inquiries into the
Silurian rocks, Hugh Miller and many others had their attention occupied
with the Old Red Sandstone--the Devonian of Sedgwick and
Murchison--which immediately overlies them. After a youth passed in
wandering among the woods and rocks of his native Cromarty, the day came
when Miller found himself twenty years of age, and, for the time, a
workman in a quarry. A hard fate he thought it at the time, but to him
it was the road to fame and success in life. The quarry in which he
laboured was at the bottom of a bay formed by the mouth of a river
opening to the south, a clear current of water on one side, as he
vividly described it, and a thick wood on the other. In this silent
spot, in the remote Highlands, a curious fossil fish of the Old Red
Sandstone was revealed to him; its appearance struck him with
astonishment; a fellow-workman named a spot where many such monuments of
a former world were scattered about; he visited the place, and became a
geologist and the historian of the “Old Red.” And what strange fantastic
forms did it afterwards fall to his lot to describe! “The figures on a
China vase or Egyptian obelisk,” he says, “differ less from the real
representation of the objects than the fossil fishes of the ‘Old Red’
differ from the living forms which now swim in our seas.”
The _Carboniferous Limestone_, which underlies the coal, the
_Coal-measures_ themselves, the _New Red Sandstone_, the _Lias_, and the
_Chalk_, have in their turn found their historians; but it would be
foreign to our object to dwell further here on these particular branches
of the subject.
Some few of the fossilised beings referred to resemble species still
found living, but the greater part belong to species which have become
altogether extinct. These fossil remains may constitute natural
families, none of the genera of which have survived. Such is the
_Pterodactyle_ among Pterosaurian reptiles; the _Ammonite_ among
Mollusca; the _Ichthyosaurus_ and the _Plesiosaurus_ among the
Enaliosaurian reptiles. At other times there are only extinct genera,
belonging to families of which there are still some genera now living,
as the genus _Palæoniscus_ among fishes. Finally, in Tertiary deposits,
we meet with some extinct species belonging to genera of our existing
fauna: the _Mammoth_, for example, of the youngest Tertiary deposits, is
an extinct species of the genus elephant.
Some fossils are terrestrial, like the gigantic Irish stag, _Cervus
Megaceros_, the snail or _Helix_; fluviatile or lacustrine, like the
_Planorbis_, the _Lymnæa_, the _Physa_, and the _Unio_; marine, or
inhabiting the sea exclusively, as the Cowry (_Cypræa_), and the Oyster,
(_Ostrea_).
Fossils are sometimes preserved in their natural state, or are but very
slightly changed. Such is the state of some of the bones extracted from
the more recent caves; such, also, is the condition of the insects found
enclosed in the fossil resins in which they have been preserved from
decomposition; and certain shells, found in recent and even in old
formations, such as the Jurassic and Cretaceous strata--in some of which
the shells retain their colours, as well as their brilliant pearly
lustre or nacre. At Trouville, in Normandy, in the Kimeridge strata,
magnificent _Ammonites_ are found in the clay and marl, all brilliant
with the colours of mother-of-pearl. In the Cretaceous beds at
Machéroménil, some species of _Ancyloceras_ and _Hamites_ are found
still covered with a nacre, displaying brilliant reflections of blue,
green, and red, and retaining an admirable lustre. At Glos, near
Liseaux, in the Coral Rag, not only the _Ammonites_, but the _Trigoniæ_
and _Aviculæ_ have preserved all their brilliant nacre. Sometimes these
remains are much changed, the organic matter having entirely
disappeared; it sometimes happens also, though rarely, that they become
petrified, that is to say, the external form is preserved, but the
original organic elements have wholly disappeared, and have been
replaced by foreign mineral substances--generally by silica or by
carbonate of lime.
[Illustration: Fig. 1.--Labyrinthodon pachygnathus and footmarks.]
Geology also enables us to draw very important conclusions from certain
fossil remains whose true nature was long misunderstood, and which,
under the name of _coprolites_, had given rise to much controversial
discussion. Coprolites are the petrified excrements of extinct fossil
animals. The study of these singular remains has thrown unexpected light
on the habits and physiological organisation of some of the great
antediluvian animals. Their examination has revealed the scales and
teeth of fishes, thus enabling us to determine the kind of food in which
the animals of the ancient world indulged: for example, the coprolites
of the great marine reptile which bears the name of _Ichthyosaurus_
contain the bones of other animals, together with the remains of the
vertebræ, or of the phalanges (paddle-bones) of other Ichthyosauri;
showing that this animal habitually fed on the flesh of its own species,
as many fishes, especially the more voracious ones, do in our days.
The imprints left upon mud or sand, which time has hardened and
transformed into sandstone, furnish to the geologist another series of
valuable indications. The reptiles of the ancient world, the turtles in
particular, have left upon the sands, which time has transformed into
blocks of stone, impressions which evidently represent the exact moulds
of the feet of those animals. These impressions have, sometimes, been
sufficient for naturalists to determine to what species the animal
belonged which thus left its impress on the wet ground. Some of these
exhibit tracks to which we shall have occasion to refer; others present
traces of the footprints of the great reptile known as the
_Labyrinthodon_ or _Cheirotherium_, whose footmarks slightly resemble
the impression made by the human hand (Fig. 1). Another well-known
impression, which has been left upon the sandstone of Corncockle Moor,
in Dumfriesshire, is supposed to be the impress of the foot of some
great fossil Turtle.
[Illustration: Fig. 2.--Impressions of rain-drops.]
We may be permitted to offer a short remark on this subject. The
historian and antiquary may traverse the battle-fields of the Greeks and
Romans, and search in vain for traces of those conquerors, whose armies
ravaged the world. Time, which has overthrown the monuments of their
victories, has also effaced the marks of their footsteps; and of the
many millions of men whose invasions have spread desolation throughout
Europe, not even a trace of a footprint is left. Those reptiles, on the
other hand, which crawled thousands of ages ago on the surface of our
planet when it was still in its infancy, have impressed on the soil
indelible proofs of their existence. Hannibal and his legions, the
barbarians and their savage hordes, have passed over the land without
leaving a material mark of their passage; while the poor turtle, which
dragged itself along the silent shores of the primitive seas, has
bequeathed to learned posterity the image and impression of a part of
its body. These imprints may be perceived as distinctly on the rocks, as
the traces left on moist sand or in newly-fallen snow by some animal
walking under our own eyes. What grave reflections should be awakened
within us at the sight of these blocks of hardened earth, which thus
carry back our thoughts to the early ages of the world! and how
insignificant seem the discoveries of the archæologist who throws
himself into ecstacies before some piece of Greek or Etruscan pottery,
when compared with these veritable antiquities of the earth!
The palæontologist (from παλαιος “ancient,” οντος “being,” λογος
“discourse”), who occupies himself with the study of animated beings
which have lived on the earth, takes careful account also of the sort of
moulds left by organised bodies in the fine sediment which has enveloped
them after death. Many organic beings have left no trace of their
existence in Nature, except their impressions, which we find perfectly
preserved in the sandstone and limestone, in marl or clay, and in the
coal-measures; and these moulds are sufficient to tell us the kind to
which the living animals belonged. We shall, no doubt, astonish our
readers when we tell them that there are blocks of sandstone with
distinct impressions of drops of rain which had fallen upon sea-shores
of the ancient world. The impressions of these rain-drops, made upon the
sands, were preserved by desiccation; and these same sands, being
transformed by subsequent hardening into solid and coherent sandstones,
their impressions have been thus preserved to the present day. Fig. 2
represents impressions of this kind upon the sandstone of Connecticut
river in America, which have been reproduced from the block itself by
photography. In a depression of the granitic rocks of Massachusetts and
Connecticut, the red sandstone occupies an area of a hundred and fifty
miles in length from north to south, and from five to ten miles in
breadth. “On some shales of the finest texture,” says Sir Charles Lyell,
“impressions of rain-drops may be seen, and casts of them in the
argillaceous sandstones.” The same impressions occur in the recent red
mud of the Bay of Fundy. In addition to these, the undulations left by
the passage of the waters of the sea, over the sands of the primitive
world, are preserved by the same physical agency. Traces of undulations
of this kind have been found in the neighbourhood of Boulogne-sur-Mer,
and elsewhere. Similar phenomena occur in a still more striking manner
in some sandstone-quarries worked at Chalindrey (Haute-Marne). The
strata there present traces of the same kind over a large area, and
along with them impressions of the excrements of marine worms. One may
almost imagine oneself to be standing on the sea-shore while the tide is
ebbing.