Principles of Geology

“ We 119 must be content with one or two examples, which may help to illustrate the process of inductive reasoning upon which the general principles of geological science are founded.
It is argued, then, that the present operations of Nature afford the best key for the interpretation of her works in bygone times. We observe various beds of rocks now in course of formation on the surface of the Earth; and within the Crust of the Earth we discover corresponding strata of the self-same rock already complete, and laid by, as it were, in Nature’s storehouse. ”

“ The publication of 'The Principles of Geology,' in 1830, constituted an epoch in geological science. But it also constituted an epoch in the modern history of the doctrines of evolution, by raising in the mind of every intelligent reader this question: If natural causation is competent to account for the not-living part of our globe, why should it not account for the living part? ”

“ Each of these facts carries us back to a period immeasurably anterior to the creation of man, as the epoch when the sedimentary deposits commenced. There are no facts in geology which point to a different conclusion. It is of the utmost importance to the geological student to familiarize himself with this principle. It will assist him in comprehending the greatness of geological changes, and in applying other principles in explanation of geological phenomena. ”

“ As geologists, we learn that it is not only the present condition of the globe which has been suited to the accommodation of myriads of living creatures, but that many former states also have been adapted to the organization and habits of prior races of beings. The disposition of the seas, continents, and islands, and the climates, have varied; the species likewise have been changed; and yet they have all been so modelled, on types analogous to those of existing plants and animals, as to indicate, throughout, a perfect harmony of design and unity of purpose. ”

“ The observations of naturalists upon living species may, in the course of future centuries, accumulate positive data, from which an insight into the laws which govern this part of our terrestrial system may be derived; but, in the present deficiency of historical records, we have traced up the subject to that point where geological monuments alone are capable of leading us on to the discovery of ulterior truths. To these, therefore, we must appeal, carefully examining the strata of recent formation wherein the remains of living species, both animal and vegetable, are known to occur. ”

“ He who has observed the quarrying of stone from a rock, and has seen it shipped for some distant port, and then endeavors to conceive what kind of edifice will be raised by the materials, is in the same predicament as a geologist, who, while he is confined to the land, sees the decomposition of rocks, and the transportation of matter by rivers to the sea, and then endeavors to picture to himself the new strata which Nature is building beneath the waters. ”

“ In many cases the problems involved are intricate, and only the trained geologist is able to at all successfully cope with them. In such cases it is necessary not only to have a thorough knowledge of minerals and rocks as such, but also of their origin and structure. Much of the practical application of geology is carried out by the mining engineer who should have, above all, a thorough knowledge of the great principles of geology. ”

“ It would be no less desirable that a geologist should be well versed in chemistry, natural philosophy, mineralogy, zoology, comparative anatomy, botany; in short, in every science relating to organic and inorganic nature. With these accomplishments, the historian and geologist would rarely fail to draw correct and philosophical conclusions from the various monuments transmitted to them of former occurrences. ”

“ The principles of physical geology come first; the several chapters are arranged in what is believed to be a natural order, appropriate to the greatest part of our country, so that from a simple beginning a logical sequence of topics leads through the whole subject. The historical view of the science comes second, with many specific illustrations of the physical processes previously studied, but now set forth as part of the story of the earth, with its many changes of aspect and its succession of inhabitants. ”

“ Every geologist, therefore, will be prepared to call in the aid of the same powerful cause, to account for the removal of a large part of the rocks which must once have occupied the interior space, in the same manner as they attribute the abstraction of matter from elliptical "valleys of elevation," such as those of Woolhope and the Wealden in England, to the waves and currents of the sea. ”

“ Division of the subject.—Geology was defined to be the science which investigates the former changes that have taken place in the organic as well as in the inorganic kingdoms of nature. As vicissitudes in the inorganic world are most apparent, and as on them all fluctuations in the animate creation must in a great measure depend, they may claim our first consideration. The great agents of change in the inorganic world may be divided into two principal classes, the aqueous and the igneous. ”

“ Their investigations had eventually a powerful effect in dispelling the illusion which had long prevailed concerning the absence of analogy between the ancient and modern state of our planet. A close comparison of the recent and fossil species and the inferences drawn in regard to their habits, accustomed the geologist to contemplate the earth as having been at successive periods the dwelling-place of animals and plants of different races, some terrestrial, and others aquatic—some fitted to live in seas, others in the waters of lakes and rivers. ”

“ The student, instead of being encouraged with the hope of interpreting the enigmas presented to him in the earth's structure,—instead of being prompted to undertake laborious inquiries into the natural history of the organic world, and the complicated effects of the igneous and aqueous causes now in operation, was taught to despond from the first. Geology, it was affirmed, could never rise to the rank of an exact science,—the greater number of phenomena must forever remain inexplicable, or only be partially elucidated by ingenious conjectures. ”

“ Erroneous theories in geology may be formed not only from overlooking the great extent of simultaneous deposits now in progress, but also from the assumption that such formations may be universal or coextensive with the bed of the ocean. ”

“ Next to determining the question whether species have a real existence, the consideration of the laws which regulate their geographical distribution is a subject of primary importance to the geologist. ”

“ It is scarcely necessary to state, that the order of events thus assumed to occur, for the sake of illustration, must be in harmony with all the conclusions legitimately drawn by geologists from the structure of the earth, and must be equally in accordance with the changes observed by man to be now going on in the living as well as in the inorganic creation. ”

“ This change in the physical geography of Europe and North America was accompanied by an alteration no less remarkable in organic life, scarcely any species being common both to the secondary and tertiary rocks, and the fossils of the latter affording evidence of a different climate. ”

“ For as, by studying the external configuration of the existing land and its inhabitants, we may restore in imagination the appearance of the ancient continents which have passed away, so may we obtain from the deposits of ancient seas and lakes an insight into the nature of the subaqueous processes now in operation, and of many forms of organic life, which, though now existing, are veiled from sight. ”

“ The composition, disposition and structure of these several sorts of rock and their fossil contents, so far as they contain fossils, interpreted in the light of processes now taking place, allow geologists to infer the conditions under which the various sorts of rocks are made. When geologists are able to tell what the conditions were on every part of the earth at every period of the past, the science of geology will be complete. ”

“ As the study of both these branches forms the subject of the science of Geology, it is no less important to examine the nature and action of the physical forces, that have affected unorganized mineral bodies, than to investigate the laws of life, and varied conditions of organization, that prevailed while the crust of our globe, was in process of formation. ”

“ It is our purpose to bring out the salient features in the history of each subkingdom of animals, beginning with the lowest or simplest, and taking up in turn the higher and higher subkingdoms. By this method the reader may easily follow the main thread of organic evolution or progressive change which runs through most of the known history of animal life of our planet, and which is so important in the science of geology. ”

“ But while thus culling freely from the dominions of other sciences, geology claims as its peculiar territory the rocky framework of the globe. In the materials composing that framework, their composition and arrangement, the processes of their formation, the changes which they have undergone, and the terrestrial revolutions to which they bear witness, lie the main data of geological history. It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet. ”

“ Independently of those ascending and descending movements which have given rise to the superposition of the limestones and clays, and by which the position of land and sea are made in the course of ages to vary, the geologist has the difficult task of allowing for the contemporaneous thinning out in one direction and thickening in another, of the successive organic and inorganic deposits of the same era. ”

“ The great object of the geologist is, by studying the geological formations in regular order, from the oldest up to the newest, to work out, in their proper sequence, the events which constitute the earth’s history; and dynamical and structural geology are merely introductory chapters, the alphabet, as it were, which must be learned before we are prepared to read understandingly the grand story of the geological record. ”

“ Others deal with the application of powers elsewhere recognised to some region of concrete facts or phenomena. Thus, geology does not discuss any natural powers not found in other sciences, but seeks to apply the laws of physics, chemistry, and biology to account for the appearance of the earth’s crust. ”

“ Geology, as will be seen from the preceding details, is among the most comprehensive of the sciences. It invades the province of every one of them, and lays them all under contribution while following out its own peculiar researches. A dry description of rocks, in their simple mineral qualities, does not limit or exhaust its ample resources. Botany, zoology, meteorology—a part, in short, of every branch of natural history, as well as chemistry, physics, and astronomy, are severally enlisted in its service, and all give interest and importance to its discursive investigations. ”

“ Geology, therefore, like all other natural sciences, is made up partly of fact, and partly of theory. It belongs to the Geologist first to investigate the phenomena which the Crust of the Earth exhibits to the eye. For this purpose he descends into the mine and the quarry; he visits the lofty cliff by the sea-shore, the deep ravine on 31 the mountain side, the cutting of a railway; in a word, every spot where a section of the Earth’s Crust is exposed to view, either by the action of Nature or by the hand of man. ”

“ The subjects I first propose to consider have no general name, and are not easily grouped under a single descriptive heading; but they may be compared with that recent development of a sister science which has been termed surface-geology or Earth-sculpture. In the older geological works we learnt much about strata, and rocks, and fossils, their superposition, contortions, chemical constitution, and affinities, with some general notions of how they were formed in the remote past ”

“ Such effects, though attributable mainly to man, are produced in some degree by all other animals.
Besides these general effects, it is the existence of organic forms that has conferred on all the sedimentary rocks their fossiliferous character. The records of the climate of each geological period, of the physical geography, of the vegetable productions, and of the animal forms by which the earth was peopled, consist in the remains of the living beings of these several periods, imbedded in the contemporaneous rock formations. ”

“ The geologist is now prepared to read the physical history—the geographical development—of any country or of any continent by means of its formations, when he has given each formation its true place in the geological record as a time scale. ”

“ Each of these statements is in harmony with the Scriptural narrative on the one hand, and with geology on the other; and, taken together, they afford an intelligible history of the introduction of man. If a geologist were to state, à priori, the conditions proper to the creation of any important species, he could only say—the preparation or selection of some region of the earth for it, and its production along with a group of plants and animals suited to it. ”

“ Thus enlarged in its views, and provided with fit means of pursuing them, Geology extends its researches into regions more vast and remote, than come within the scope of any other physical science except Astronomy. It not only comprehends the entire range of the mineral kingdom, but includes also the history of innumerable extinct races of animals and vegetables ”