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FOSSILS — THETE NATTJEE AND
AEEANGEMENT.

THE TERMS FOSSIL AND SUB-FOSSIL—SCIENCE OF PALAEONTOLOGY—
FOSSILS, HOW IMBEDDED AND PRESERVED— THEIR IMPORTANCE
IN GEOLOGY — INDICATORS OF GEOGRAPHICAL CONDITIONS IN
THE PAST — OF NATURE AND KIND OF LIFE DURING SUCCESSIVE
PERIODS OF WORLD-HISTORY — DIFFICULTIES ATTENDING FALJE-
ONTOLOGICAL RESEARCH — ORGANISMS MOST PERFECTLY PRE-
SERVED— PROCESSES OF PETRIFACTION — CONDITIONS IN WHICH
FOSSILS USUALLY OCCUR — REQUISITE SKILL FOR THEIR INTER-
PRETATION —. BOTANICAL AND ZOOLOGICAL ARRANGEMENT OF—
THIS PRELIMINARY KNOWLEDGE NECESSARY TO THE STUDY OF
GENERAL GEOLOGY.

Whatever may have teen the meaning which our forefathers attached to the term, fossil (Lat. fossilis, dug up), every man and woman of ordinary intelligence now understands that it refers to the remains of plants and animals found in the crust of the earth, and more or less petrified or converted into stony matter. Where these remains— whether trunks, branches, or leaves, bones, teeth, or shells— occur in recent and superficial accumulations, they appear little altered in texture, and are usually looked upon as sub-fossil, or only partially fossil; but when they are imbedded in the older and harder strata, the stony conversion is in general complete, and they are then regarded as true fossils or petrifactions. Wherever they are found their history excites a lively interest; and minds altogether unattracted by the physical record of the earth are often excited to enthusiasm in the search of its organic memorials. Their study is, in fact, a kind of archaeology-—an antiquarianism like that which attaches to ruins and burialmounds, but of a broader and more marvellous description. To the older geologists their occurrence was a riddle, and few considered tbem as other than mere accidents or lusus natures; but to the modern geologist they are replete with information of the world's past, revealing to him the kind of life that peopled its lands and waters during the successive stages of its history, and, by inference, the geographical conditions under which they flourished and declined. The recognition of their nature and importance has thrown a new and higher interest round geology; and where the study of mere rocks and minerals formerly shed an uncertain glimmer, the science of fossils has cast the light of sure and satisfactory information. This science of fossils, or Palceontology, as it is technically termed (Gr. palaios, ancient; onta, beings; and logos, discourse or reasoning), is now, indeed, one of the main sections of geology; for if geology be world-history, that history can never be written without a knowledge of the plants and animals that have successively peopled the earth, as well as of the external conditions which the nature of these plants and animals alone can indicate. It is necessary, then, that the student of popular geology should know what fossils really are, the various states in which they occur, and the manner in which they can be arranged according to the classifications of the botanist and geologist. To these subjects we devote the present Sketch,—premising that Palaeontology may be technically subdivided into Palceophytology, or the science of fossil plants, and Palaiozoology, or the science of fossil animals; though, for all ordinary purposes, the general term is sufficiently comprehensive and intelligible.

Like other things in the history of the earth, the nature and occurrence of fossils will be best explained by an appeal to the existing operations of nature. If we stand by the side of a river, and especially when it is in flood, we perceive that the current is continually bearing onward vegetable and animal debris, and that this debris is gradually entombed among the mud, sand, and gravel which the river deposits in the lake, estuary, or sea into which it discharges its waters. As with one river, so with every rill and river that traverses the terrestrial surface — each is carrying down the spoil's of the land in a state more or less fragmentary, and burying them in the silt, where, excluded from atmospheric decay, they appear in the first stages of fossilisation. As with land-plants and animals, so with those of lakes and seas; they die and are imbedded in sediments where they lived and grew, or are drifted by tides and currents to some distant locality. This process is ever going forward in every region — tropical, temperate, and arctic; and as each region is characterised by its own special flora and fauna, the imbedded remains will indicate to future observers the external conditions under which they grew and were deposited. The plants and animals entombed. in the estuary of the Amazon must differ from those deposited in the delta of the Mississippi, and these again from those preserved in the mud-islands of the Niger, the Ganges, and other Old World rivers. The shells, crustacea, and fishes that die and sink in the sediments of tropical seas differ widely from those of temperate waters, and these again as widely from the fauna of the Arctic and Antarctic Oceans. As it is now, so it must have been in all former ages, and thus the fossils of the stratified formations become the only clue to the geographical conditions of the areas in which they were deposited, and of the regions from which they were derived.

Nor is it geographical or climatic condition alone of which

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these fossil relics bear evidence. Every family of plants has its own peculiar station—the waters, the marsh, the plain, the upland, or the shingly desert; and every family of animals its own special habitat—the forest, the open plain, the shallow lake, the sandy or muddy shore, or the greater ocean-depths. As these families are regulated now, so the paleontologist presumes they were governed in former epochs, and thus by a critical study of his fossils he arrives at a more vivid picture of the past, and can associate with each order and family the general features 6f their physical surroundings. From his knowledge of the present he rises to a true conception of the past, and from his acquaintance with the existing he can indicate with something like certainty the habitats and distribution of the extinct. It is true there will be occasional comminglings of terrestrial and aquatic remains, of fresh-water and marine, just as now the spoils of the land may be mingled with those of the estuary, and those of the river with those of the ocean; but in general such commixtures are limited, and do not obliterate the broader characteristics of the formations in which they occur. Here and there the record may be complicated; it is never equivocal or disguised.

Nor is it mere habitat and distribution the palaeontologist can thus arrive at; but habit and function are also determinable by the requisite anatomical skill. The forelimb to swim, the forelimb to walk, the forelimb to run, the forelimb to seize, and the forelimb to fly, are each stamped by its own essential characteristics, just as the herbivorous, the carnivorous, and the insectivorous teeth are; and thus the competent palaeontologist is enabled to recall not only the physical surroundings of his fossil flora and fauna, but their forms and functions—presenting a picture of the world's past like that which the geographer presents of its existing phenomena. There are few things, indeed, which science has greater cause to boast of than this determination and restoration of fossil forms. From a few stray chips and fragments to reveal the nature of the plant or animal to which these fragments belong, or from a few scattered bones and teeth to reconstruct the form of the creature and indicate its habits and functions, is, in truth, the triumph of modern anatomy. "Every organised being" says the immortal Cuvier, "forms a whole, a single circumscribed system, the parts of which mutually correspond and concur to the same definite action by a reciprocal reaction. None of these parts can change without the others also changing, and consequently each part, taken separately, indicates and gives all the others." In this truth lies the fundamental law of the co-relation of parts, the discovery of which enabled the great French anatomist to effect his wonderful restorations of the mammals of the Paris Basin, and the enunciation of which has ever since thrown the light of hope and of certainty over the toilsome labours of the palaeontologist. To him fossils became, as they have been eloquently and appropriately termed, the Medals Of Creation; "for as an accomplished numismatist, even when the inscription of an ancient and unknown coin is illegible, can from the half-obliterated effigy, and from the style of art, determine with precision the people by whom and the period when it was struck; so in like manner the geologist can decipher these natural memorials, interpret the hieroglyphics with which they are inscribed, and, from apparently the most insignificant relics, trace the history of beings of whom no other records are extant, and ascertain the forms and habits of unknown types of organisation, whose races were swept from the face of the earth thousands of ages before the creation of man and the creatures which are his contemporaries." *

* Mantell's * Medals of Creation,' vol. i. p. 17.

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