The Rise of Geology in Europe
Mineral Geology.—The geological sciences had their rise in the study of minerals as carried on by the German chemist and physician George Bauer (1494–1555), better known as Agricola. Bauer originated the critical study of minerals, but did not distinguish his “fossilia,” the remains of organisms, from the inorganic crystal forms. Mineral geology endured until the close of the eighteenth century.
Cosmogonists.—Then came the expounders of the earth’s origin, the cosmogonists of the sixteenth to the end of the eighteenth centuries. The fashion of this time was to write histories of the earth derived out of the imagination.
Earliest Historical Geology.—Even though Giovanni Arduino (1713–1795) of Padua was not the first to classify the rocks into three series according to their age, he did this more clearly than any one else before his time. The rocks about Verona he grouped in 1759 into Primary, Secondary, Tertiary, and Volcanic. This three-fold classification came into general use, though modified with time.
Early in the nineteenth century it had become plain that formations of very varying ages were included in each one of the three series. Through the study of the fossils and the recognition of the fact that mountain ranges have been raised at various times, causing younger fossiliferous strata to take on the characters of the Primary, it was seen that these terms of Arduino had lost their original significance.
The first one to describe in detail a local stratigraphic sequence was Johann Gottlob Lehmann (died 1767). In 1756 he published “one of the classics of geological literature,” distinguishing clearly thirty successive sedimentary deposits, some of which he said had fossils, but he did not use them to distinguish the strata.
What Lehmann did for the Permian system, George Christian Füchsel (1722–1773) did even better for the Triassic of Thuringia, in 1762 and 1773. He pointed out not only the sequence, but also how the gently inclined strata rest upon the older upturned masses of the mountains; also that some formations have only marine fossils, while others have only terrestrial forms and thus indicate the proximity of land. The deformed strata he thought had fallen into the hollows within the earth, great caverns that had also consumed much of the oceanic waters and had in so doing greatly lowered the sea-level. It was Füchsel who first introduced the theory of universal formations, and who defined the term formation, using it as we now do, system or period. Even though Lehmann and Füchsel showed that there was a definite order and process in the formation of the earth’s crust, their example was barren of followers until the beginning of the eighteenth century.
Wernerian Geology or Geognosy.—We come now to the time of Abraham Gottlob Werner (1749–1817), who from 1775 to 1817 was professor of mining and mineralogy in the Freiberg Academy of Mines. Geikie, in his most interesting Founders of Geology, says that Werner “bulks far more largely in the history of geology than any of those with whom up to the present we have been concerned—a man who wielded an enormous authority over the mineralogy and geology of his day.” “Although he did great service by the precision of his lithological characters and by his insistence on the doctrine of geological succession, yet as regards geological theory, whether directly by his own teaching, or indirectly by the labors of his pupils and followers, much of his influence was disastrous to the higher interests of geology.”
Werner arranged the crust of the earth into a series of formations, as had been done previously by Lehmann and Füchsel, and one of his fundamental postulates was that all rocks were chemically precipitated in the ocean as “universal formations.” For this reason Werner’s school were called the Neptunists. Nowhere, however, did he explain how and where the deep and primitive ocean had disappeared.
According to Werner, the first formed or oldest rocks were the chemically deposited Primitive strata, including granite and other igneous and metamorphic rocks. On these followed the Transition rocks, the earliest sediments of mechanical origin, and above them the Floetz rocks, a term for the horizontal stratified rocks. These last he said were partly of chemical but chiefly of mechanical origin. Last of all came the Alluvial series.
The existence of volcanoes had been pointed out long before Werner’s time by the Italian school of geologists, but as for “the universality and potency of what is now termed igneous action,” all was “brushed aside by the oracle of Freiberg.” Reactions between the interior and exterior of our earth “were utterly antagonistic to Werner’s conception of the structure and history of the earth.” To him, volcanoes were “burning mountains” that arose from the combustion of subterranean beds of coal, spontaneously ignited.
The breaking down of the Wernerian doctrines began with two of Werner’s most distinguished pupils, D’Aubuisson de Voisins (1769–1819) and Von Buch. The former in 1803 had accepted Werner’s aqueous origin of basalt, but after studying the celebrated and quite recent volcanic area of Auvergne he recanted in 1804. Here he saw the basaltic rocks lying upon and cutting through granite, and in places more than 1200 feet thick. “If these basaltic rocks were lavas,” says Geikie, “they must, according to the Wernerian doctrine, have resulted from the combustion of beds of coal. But how could coal be supposed to exist under granite, which was the first chemical precipitate of a primeval ocean?”
Leopold von Buch (1774–1853), “the most illustrious geologist that Germany has produced,” after two years spent in Norway was satisfied “that the rocks in the Christiania district could not be arranged according to the Wernerian plan, which there completely broke down. Von Buch found a mass of granite lying among fossiliferous limestones which were manifestly metamorphosed, and were pierced by veins of granite, porphyry, and syenite.” Even so, he was not ready to abandon the teachings of his master. After a study of the mountain systems of Germany, however, “he declared that the more elevated mountains had never been covered by the sea, as Werner had taught, but were produced by successive ruptures and uplifts of the terrestrial crust” (Geikie).
Rise of Geology and Conformism.—Modern geology has its rise in James Hutton (1726–1797) of Edinburgh, Scotland. In 1785 and 1795, Hutton published his Theory of the Earth, with Proofs and Illustrations. His “immortal theory” is his only work on geology. “Fortunately for Hutton’s fame and for the onward march of geology, the philosopher numbered among his friends the illustrious mathematician and natural philosopher, John Playfair (1748–1819), who had been closely associated with him in his later years, and was intimately conversant with his geological opinions.” In 1802, Playfair published his Illustrations of the Huttonian Theory of the Earth, of which Geikie says, “Of this great classic it is impossible to speak too highly,” as it is at the basis of all modern geology.
One of Hutton’s fundamental doctrines is that the earth is internally hot and that in the past large masses of molten material, the granites, have been intruded into the crust. It was these igneous views that led to his followers being called the Plutonists. Another of his great doctrines was that “the ruins of an earlier world lie beneath the secondary strata,” and that they are separated by what is now known as unconformity. He clearly recognized a lost interval in the broken relation of the structures, and that the ruins, the detrital materials, of one world after another are superposed in the structure of the earth.
Hutton also held that the deformation of once horizontally deposited strata was probably brought about at different periods by great convulsions that shook the very foundations of the earth. After a convulsion, there was a long time of erosion, represented by the unconformity. Geikie says, “The whole of the modern doctrine of earth sculpture is to be found in the Huttonian theory.”
The Lyellian doctrine of metamorphism had its origin in Hutton, for he showed that invading igneous granite had altered, through its heat and expanding power, the originally waterlaid sediments, and that the schists of the Alps had been born of the sea like other stratified rocks.
Hutton is the father of the Uniformitarian principle, for he “started with the grand conception that the past history of our globe must be explained by what can be seen to be happening now, or to have happened only recently. The dominant idea in his philosophy is that the present is the key to the past.” This principle has been impressed on all later geologists by Sir Charles Lyell, and is the chief cornerstone of modern geology.
The principle of uniformitarianism has underlain geologic interpretation since the days of Hutton, Playfair, and Lyell. However, it is often applied too rigidly in interpretations based upon the present conditions, because in the past there were long times when the topographic features of the earth were very different from those of to-day. Throughout the Paleozoic, and, less markedly, the Mesozoic, the oceans flooded the lands widely (at times over 60 per cent of the total area), highlands were inconspicuous, sediments far scarcer, and climates warm and equable throughout the world. Highland conditions, and especially the broadly emergent continents of the present, were only periodically present in the Paleozoic and then for comparatively short intervals between the periods. Therefore rates of denudation, solution, sedimentation, and evolution have varied greatly throughout the geological ages. These differences, however, relate to degrees of operation, and not to kinds of processes; but the differences in degree of operation react mightily on our views as to the age of the earth.
Geologic time had, for Hutton, no “vestige of a beginning, no prospect of an end.” In other words, geologic time is infinite. He did not, however, discover a method by which the chronology of the earth could be determined.
First Important Text-books.—In 1822 appeared the ablest text-book so far published, and the pattern for most of the later ones, Outlines of the Geology of England and Wales, by W. D. Conybeare (1787–1857) and W. Phillips (1775–1828). “In this excellent volume all that was then known regarding the rocks of the country, from the youngest formations down to the Old Red Sandstone, was summarized in so clear and methodical a manner as to give a powerful impulse to the cultivation of geology in England” (Geikie). This book is reviewed at great length by Edward Hitchcock in the Journal (7, 203, 1824).
To indicate how far historical geology had progressed up to 1822 in England, a digest of the geological column as presented in this text-book is given in the following table, along with other information.
A text-book writer of yet greater influence was Charles Lyell (1797–1875), whose Principles of Geology appeared in three volumes between 1830 and 1833. This and his other books were kept up to date through many editions, and his Elements of Geology is, as Geikie says, “the hand book of every English geologist” working with the fossiliferous formations.