Page images

of science. His share in the classification and description of the coming to it with certain preconceived notions, which affected all mollusca and in founding invertebrate palaeontology, his theory his subsequent writings. While Lamarck was by instinct an evoluof organic evolution and his philosophical treatment of many tionist, who sought to trace in the history of the past the operation biological questions have been tardily recognized, but his contribue of the same natural processes as are still at work, Cuvier, on the tions to geology have been less generally acknowledged. When he other hand, was a catastrophist, who invoked a succession of vast accepted the professorship of zoology; of insects, of worms and of cataclysms to account

for the interruptions in the continuity

of the microscopic animals at the Museum of Natural History, Paris, geological record. in 1793, he at once entered with characteristic ardour and capacity In a preliminary Discourse prefixed to his Recherches sur les into the new field of research then opened to him. In dealing with ossemens fossiles (1821). Cuvier gave an outline of what he conceived the mollusca he considered pot merely the living but also the extinct to have been the past history of our globe, so far as he had been able and species furnished by the Tertiary deposits of the Paris of France. He believed that in that history, evidence can be of which he published descriptions and plates that proved of essential recognized of the occurrence of many sudden and disastrous revoluservice in the stratigraphical work of Cuvier and Alexandre tions, which, to judge from their effects on the animal life of the Brongniart (1770-1847). His labours among these relics of ancient time, must have exceeded in violence anything we can conceive at seas and lakes led him to ponder over the past history of the globe, the present day, and must have been

brought about by other agencies and as he was seldom dilatory in making known the opinions he had than those which are now in operation. Yet, in spite of these formed, he communicated some of his conclusions to the National catastrophes, he saw that there has been an upward progress in the Institute in 1799. These, including a further elaboration of his animal forms inhabiting the globe, until the series ended in the views, he published in 1802 in a small volume entitled Hydrogéologie. advent of man. He could not, however, find any evidence that one

This treatise, though it did not reach a second edition and has species has been developed from another, for in that case there should never been reprinted, deserves an honourable place in geological have been traces of intermediate forms among the stratified forma. literature. Its object, the author states, was to present some im- tions, where he affirmed that they had never been found. A portant and novel considerations, which he thought should form prominent position in the Discourse is given to a strenuous argument The basis of a true theory of the earth. He entirely agreed with the to disprove the alleged antiquity of some nations, and to show that doctrine of the subaerial degradation of the land and the erosion of the last great catastrophe occurred. not more than some 5000 or valleys by running water. Not even Playfair could have stated this 6000 years ago. Cuvier thus linked himself with those who in doctrine more emphatically, and it is worthy of notice that Playfair's previous generations had contended for the efficacy of the Deluge. Illustrations of the Hultonian Theory appeared in the same year But his researches among fossil animals had given him a far wider with Lamarck's book. The French naturalist, however, carried his outlook into the geological past, and had opened up to him a succonclusions so far as to take no account of any great movements of cession of deeply interesting problems in the history of life upon the the terrestrial crust, which might have produced or modified the earth, which, though he had not himself material for their solution, main physical features of the surface of the globe. He thought that he could foresee would be cleared up in the future. all mountains, except such as were thrown up by volcanic agency or Gradual Shaping of Geology into a Distinct Branch of Science.---It local accidents, have been cut out of plains, the original surfaces of will be seen from the foregoing historical sketch that it was only which are indicated by the crests and summits

of these elevations. after the lapse of long centuries, and from the labours of many Lamarck, in reflecting upon the wide diffusion of fossil shells and successive generations of observers and writers, that what we now the great height above the sea at which they are found, conceived know as the science of geology came to be recognized as a distinct the extraordinary idea that the ocean basin has been scoured out department of natural knowledge, founded upon careful and ex. by the sea, and that, by, an impulse communicated to the waters tended study of the structure of the earth, and upon observation of through the influence chiefly of the moon, the sea is slowly eating the natural

processes, which are now at work in changing the earth's away the eastern margins of the continents, and throwing up detritus surface. The term "geology," descriptive of this branch of the on their western coasts, and is thus gradually shifting its basin investigation of nature, was not proposed until the last quarter of round the globe. He would not admit the operation of cataclysms; the 18th century by Jean André De Luc (1727-1817) and Horace but insisted as strongly as Hutton on the continuity of natural Benedict De Saussure (1740-1749). But the science was then in a processes, and on the necessity of explaining former changes of the markedly hall-formed condition, theoretical speculation still in large earth's surface by causes which can still be seen to be in operation. part supplying the place of deductions from a detailed examination As might be anticipated from his previous studies, he brought living of actual fact. In 1807 a few enterprising spirits founded the things and their remains into the forefront of his theory of the earth. Geological Society of London for the special purpose of counterHe looked upon fossils as one of the chief means of comprehending acting the prevalent tendency and confining their intention to the revolutions which the surface of the earth has undergone; investigate the mineral structure of the earth." The cosmogonists and in his little yolume he again and again dwells on the vast and framers of Theories of the Earth were succeeded by other schools antiquity to which these revolutions bear witness. He acutely of thought. The Catastrophists saw in the composition of the crust argues, from the condition of fossil shells, that they must have lived of the earth distinct evidence that the forces of nature were once and died where their remains are now found.

much more stupendous in their operation than they now are, and In the last part of his treatise Lamarck advances some peculiar that they had from time to time devastated the earth's surface; opinions in physics and chemistry, which

he had broached eighteen extirpating the races of plants and animals, and preparing the ground years before, but which had met with no acceptance among the for new creations of organized life. Then came the Uniformitarians, scientific men of his time. He believed that the tendency of all who, pushing the doctrines of Hutton to an extreme which he did compound substances is to decay, and thereby to be resolved into not propose, saw no evidence that the activity of the various geotheir component constituents. Yet he saw that the visible crust logical causes has ever seriously differed from what it is at present. of the earth consists almost wholly of compound bodies. He there. They were inclined to disbelieve that the stratified formations of fore set himself to solve the problem thus presented. Perceiving the earth's crust furnish conclusive evidence of a gradual prothat the biological action of living organisms is constantly forming gression, from simple types of life in the oldest strata to the most combinations of matter, which would never have otherwise come highly developed forms in the youngest; and saw no reason why into existence, he proceeded to draw the extraordinary conclusion remains of the higher vertebrates should not be met with among that the action of plant and animal life (the Pouvoir de la vie) upon the Palacozoic formations. Sir Charles Lyell (1797-1875) was the the inorganic world is so universal and so potent, that the rocks and great leader of this school. His admirably clear and philosophical minerals which form the outer part of the earth's crust arc all, presentations of geological facts which, with unwearied industry, without exception, the result of the operations of once living bodies. he collected from the writings of observers in all parts of the world, Though this sweeping deduction must be allowed to detract from impressed his views upon the whole English-speaking world, and the value of Lamarck's work, there can be no doubt that he realized, gave to geological science a coherence and interest which largely more fully than any one had done before him, the efficacy of plants accelerated its progress. In his later years, however, he frankly and animals az agents of geological change.

The last notable contributor to the cosmological literature of accepted the views of Darwin in regard to the progressive character geology was another illustrious Frenchman, the comparative ana. The youngest of the schools of geological thought is that of the

tomist Cuvier (1769-1832). He was contemporary with Evolutionists. Pointing to the whole body of evidence from in

Lamarck, but of a very different type of mind. The organic and organic nature, they maintain that the history of our brilliance of his speculations, and the charm with which he expounded planet has been one of continual and unbroken development from them, early gained for him a prominent place in the society of Paris.

the earliest cosmical beginnings down to the present time, and that He too was drawn by his zoological studies to investigate fossil the crust of the earth contains an abundant, though incomplete, organic remains, and to consider the former conditions of the earth's record of the successive stages through which the plant and animal surface, of which they are memorials. It was among the vertebrate organisms of the Paris basin that he found his chief material, and ' In De Luc's Lettres physiques et morales sur les montagnes (1778), Irom them that he prepared the memoirs which led to him being the word "cosmology is used for our science, the author stating regarded as the founder of vertebrate palaeontology. But beyond that " geology is more appropriate, but it was not a word in use. their biological interest, they awakened in him a keen desire to in a completed edition, published in 1779, the same statement is ascertain the character and sequence of the geographical revolutions made, but geology occurs in the text; in the same year De to which they bear witness. He approached the subject from an Saussure used the word without any explanation, as if it were opposite and less philosophical point of view than that of Lamarck, well known.



kingdoms have reached their existing organization. The publication the same opinions were styled “Plutonists," or, especially where of Darwin's

Origin of Species in 1859. in which evolution was made they concerned themselves with the volcanic origin of basalt, “ Vul. the key to the history of the animal and vegetable kingdoms, pro- canists. The geological world was thus divided into two hostile duced an extraordinary revolution in geological opinion. The older camps, that of the Neptunists or Wernerians, and that of the schools of thought rapidly died out, and evolution became the Plutonists, Vulcanists or Huttonians. recognized creed of geologists all over the world.

After many years of futile controversy the first serious weakening Development of Opinion regarding Igneous Rocks.-So long as the of the position of the dominant Neptúnist school arose from the idea prevailed that volcanoes are caused by the combustion of defection of some of the most prominent of Werner's pupils. In inflammable substances underground, there could be no rational particular Jean François D'Aubuisson de Voisins (1769-1819), who conception of volcanic action and its products. Even so late as had written a treatise on the aqueous origin of the basalts of Saxony, the middle of the 18th century, as above remarked, such a good went afterwards to Auvergne, where he was speedily a convert to observer as Lazzaro Moro drew so little distinction between volcanic the views expounded by Desmarest as to the volcanic nature of and other rocks that he could believe the fossiliserous formations basalt. Having thus to relinquish one of the fundamental articles to have been mainly formed of materials ejected from eruptive vents. of the Freiberg laith, he was subsequently led to modify hisadherence After his time the notion continued to prevail that all the rocks which to others until, as he himself consessed, his views came almost wholly form the dry land were laid down under water. Even streams of to agree with those of Hutton. Not less complete, and even more lava, which were seen to flow from an active crater, were regarded important, was the conversion of the great Leopold von Buch (1774only as portions of sedimentary or other rocks, which had been 1853). He, too, was trained by Werner himself, and proved to be melted by the servent heat of the burning inflammable materials the most illustrious pupil of the Saxon professor. Full of admiration that had been kindled underground. In spite of the speculations for the Neptunism in which he had been reared, he, in his earliest of Descartes and Leibnitz, it was not yet generally comprehended separate work, maintained the aqueous origin of basalt, and conthat there exists beneath the terrestrial crust a molten magma, trasted the wide field opened up to the spirit of observation by his which, from time to time, has been injected into that crust, and has master's teaching with the narrower outlook offered by " the volcanic picrced through it, so as to escape at the surface with all the energy theory." But a little further acquaintance with the facts of nature of an active volcano. What we now recognize to be memorials of led Von Buch also to abandon his earlier prepossessions. It was a these former injections and propulsions were all confounded with the personal visit to the volcanic region of Auvergne that first opened rocks of unquestionably aqueous origin. The last great teacher by his eyes, and led him to recant what he had believed and written whom these antiquated doctrines were formulated into a system about basalt. But the abandonment of so essential a portion of the

and promulgated to the world was Abraham Gottlob Wernerian creed prepared the way for further relinquishments.

Werner (1749-1815), the most illustrious German mineral- When a few years later he went to Norway and found to his astonish. ogist and geognost of the second half of the 18th century. While ment that granite, which he had been taught to regard as the oldest still under twenty-six years of age, he was appointed teacher of chemica! precipitate from the universal ocean, could there be seen mining and mineralogy at the Mining Academy of Freiberg in Saxony to have broken through and metamorphosed fossiliferous limestones, a post which he continued to fill up to the end of his life. Possessed and to have sent veins into them, his faith in Werner's order of the of great enthusiasm for his subject, clear, methodical and eloquent succession of the rocks in the carth's crust received a further moment. in his exposition of it, he soon drew around him men from all parts ous shock. While one after another of the Freiberg doctrines of the world, who repaired to study under the great oracle of what crumbled away before him, he was now able to interrogate nature he called geognosy (Gr. y. the earth, yrwors, knowledge) or earth. on a wider field than the narrow limits of Saxony, and he was thus knowledge. Reviving doctrines that had been current long before gradually led to embrace the tenets of the opposite school. His his time, he taught that the globe was once completely surrounded commanding position, as the most accomplished geologist on the with an ocean, from which the rocks of the earth's crust were continent, gave great importance to his recantation of the Neptunist deposited as chemical precipitates, in a certain definite order over creed. His defection indeed was the severest blow that this creed the whole planet. Among these " universal formations " of aqueous had yet sustained. It may be said to have rung the knell of origin were included many rocks, which have long been recognized Wernerianism, which thereafter rapidly declined in influence, while to have been once molten, and to have risen from below into the Plutonism came steadily to the front, where it has ever since remained. upper parts of the terrestrial crust. Werner, following the old Although Desmarest had traced in Auvergne a long succession tradition, looked upon volcanoes as modern features in the history of volcanic eruptions, of which the oldest went back to a remote of the planet, which could not have come into existence until a period of time, and although he had shown that this succession, sufficient amount of vegetation had been buried to furnish fuel for coupled with the records of contemporaneous denudation, might their maintenance. Hence he attached but little importance to be used in defining cpochs of geological history, it was not until them, and did not include in his system of rocks any division of many years after his day that volcanic action came to be recognized volcanic or igneous materials. From the predominant part assigned as a normal part of the mechanism of our globe, which had been in by him to the sea in the accumulation of the materials of the visible operation from the remotest past, and which had lest numerous part of the earth, Werner and his school were known as “Neptunists.' records among the rocks of the terrestrial crust. During the progress

But many years before the Saxon professor began to teach, clear of the controversy between the two great opposing factions in the evidence had been produced from central France that basalt, one later portion of the 18th and the first three decades of the 19th

of the rocks claimed by him as a chemical precipitate and century, those who espoused the Vulcanist cause were intent on Origla of

a universal formation, is a lava which has been poured proving that certain rocks, which are intercalated among the

out in a molten state at various widely separated periods stratified formations and which were claimed by the Neptunists as of time and at many different places. So far back as 1752 J. E. obviously formed by water, are nevertheless of truly igneous origin. Guettard (1715-1786) had shown that the basaltic rocks of Auvergne | These observers (ixed their eyes on the evidence that the material of are true lavas, which have flowed out in streams from groups of such rocks, instead of having been deposited from aqueous solution, once active cones. Eleven years later the observation was confirmed had once been actually molten, and had in that condition been thrust and greatly extended by Nicholas Desmarest (1725-1815), who, between the strata, had enveloped portions of them, and had induring a long course of years, worked out and mapped the com- durated or otherwise altered them. They spoke of these masses plicated volcanic records of that interesting region, and demonstrated as "unerupted lavas"; and undoubtedly in innumerable instances to all who were willing impartially to examine the evidence the true they were right. But their zeal to establish an intrusive origin led volcanic nature of basalt. These views found acceptance from some them to overlook the proofs that some intercalated sheets of igneous observers, but they were vehemently opposed by the followers of material had not been injected into the strata, but had been poured Werner, who, by the force of his genius, made his theoretical con- out at the surface as truly volcanic discharges, and therefore belonged ceptions predominate all over Europe. The controversy as to the to the ancient periods represented by the strata between which they origin of basalt was waged with great vigour during the later decades are interposed. It may readily be supposed that any proofs of the of the 18th century. Desmarest took no part in it. He had accu- contemporaneous intercalation of such sheets would be eagerly mulated such conclusive proof of the correctness of his deductions, seized upon by the

Neptunists in favour of their aqueous theory: and had so fully expounded the clearness of the evidence in their | The influence of the ancient belief that “burning mountains savour furnished by the region of Auvergne, that, when any one could only rise from the combustion of subterranean inflammable came to consult him on the subject, he contented himself with giving materials extended even into the ranks of the Vulcanists, so far at the advice to "go and see.' While the debate was in progress least as to lead to a general acquiescence in the assumption that on the continent, the subject was approached (rom a new and volcanoes appeared to belong to a late phase in the history of the independent point of view by Hutton in Scotland. This illustrious planet. It was not until after considerable progress had been made philosopher, as already stated, realized the importance of the internal in determining the palaeontological distinctions and order of sucheat of the globe in consolidating the sedimentary rocks, and believed cession of the stratified formations of the earth's crust that it became that molten material from the earth's interior has been protruded possible to trace among these formations a succession of volcanic from below into the overlying crust. Some of the material thus episodes which were contemporaneous with them. In no part of injected could be recognized, he thought, in granite and in the the world has an ampler record of such episodes been preserved than various dark massive rocks which, known in Scotland under the in the British Isles. It was natural, therefore, that the subject name of " whinstone," were afterwards called "Trap" and are now should there receive most attention. As far back as 1820 Ami Boué Souped under various names, such as basalt, dolerite and diorite. (1794-1881) showed that the Old Red Sandstone of Scotland includes the geological evolution of the planet, that he and those who adopted origina are associated with the Carboniferous formations. H. T.


de la Beche (1796-1855) afterwards traced proofs of contemporaneous the first and more disturbed series, and are full of petrified remains eruptions among the Devonian rocks of the south-west of England. of plants and animals. Lastly he included the mountains which Adam Sedgwick (1785-1873) showed, first in the Lake District, have from time to time been formed by local accidents. Still more and afterwards in North Wales, the presence of abundant volcanic advanced were the conceptions of G. C. Füchsel, who in the year sheets among the oldest divisions of the Palacozoic series; while 1762 published in Latin A History of the Earth and the Sea, based on Roderick Impey Murchison (1792–1871) made similar discoveries e History of the Mountains of Thuringig; and in 1773. in German, among the Lower Silurian rocks. From the time of these pioneers a Skelch of the most Ancient History of the Earth and Man. In these the volcanic history of the country has been worked out by many works he described the stratigraphical relations and general char. observers until it is now known with a fulness as yet unattained acters of the various geological formations in his little principality in any other region.

and taking them as indicative of a general order of succession, he Growth of Opinion regarding Earthquakes. We have seen how traced what he believed to have been a series of revolutions through crude were the conceptions of the ancients regarding the causes of which the carth has passed. In interpreting this geological history, volcanic action, and that they connected volcanoes and earthquakes he laid great stress on the evidence of the fossils contained in the as results of the commotion of wind imprisoned within subterranean rocks. He recognized that the various formations differ from each caverns and passages. One of the carliest treatiscs, in which the other in their enclosed organic remains, and that from these dif. phenomena of terrestrial movements were discussed in the spirit ferences the existence of former sea-bottoms and land surfaces can of modern science, was the posthumous collection of papers by be determined. Robert Hooke (1635-1703), entitled Lectures and Discourses of The labours of these pioneers paved the way for the advent Earthquakes and Subterranean Eruplions, where the probable agency of Werner. Though the system evolved by this teacher claimed to of earthquakes in upheaving and depressing land is fully considered, discard theory and to be established on a basis of observed facts, but without any definite pronouncement as to the author's concep-it rested on a succession of hypotheses, for which no better foundation tion of its origin. Hooke still associated earthquakes with volcanic could be shown than the belief of their author in their validity, action, and connected both with what he called the general con Starting from the extremely limited stratigraphical range displayed gregation of sulphurous subterraneous vapours.". He conceived in the geological structure of Saxony, he took it as a type for the rest that some kind of fermentation " takes place within the earth, of the globe, persuading himself and impressing upon his followers and that the materials which catch fire and give rise to eruptions that the rocks of that small kingdom were to be taken as examples or earthquakes are analogous to those that constitute gunpowder. of his " universal formations." The oldest portion of the series, The first essay wherein earthquakes are treated from the modern classed by him as “ Primitive," consisted of rocks which he main point of view as the results of a shock that sends waves through the tained had been deposited from chemical solution. Yet they crust of the earth was written by the Rev. John Michell, and com- included granite, gneiss, basalt, porphyry and serpentine, which, municated to the Royal Society in the year 1760. Still under the even in his own day, were by many observers correctly regarded old misconception that volcanoes are due to the combustion of as of igncous origin. A later group of rocks, to which he gave the inflammable materials, which he thought might be set on fire by the name of "Transition." comprised, in his belief, partly chemical, spontaneous combustion of pyritous strata, he supposed that, by the partly mechanical sediments, and contained the earliest fossil sudden access of large bodies of water to these subterrancan fires, organic remains. A third group, for which he reserved Lehmann's vapour is produced in such quantity and with such force as to givenaine “ Flotz," was made up chiefly of mechanical detritus, while rise to the shock. From the centre of origin of this shock waves, youngest of all came the “ Alluvial" series of loams, clays, sands, he thought, are propagated through the earth, which are largest gravels and peat. It was by the gradual subsidence of the ocean at the start and gradually diminish as they travel outwards. By that, as he believed, the general mass of the dry land emerged, the drawing lines at different places in the direction of the track of these first formed rocks being left standing up, sometimes on end, to form waves, he believed that the place of common intersection of these the mountains, while those of later date, less steeply inclined, lines would be nearly the centre of the disturbance. In this way he occupied successively lower levels down to the flat alluvial accumula. showed that the great Lisbon earthquake of 1755 had its focus under tions of the plains. Neither Werner, nor any of his followers, the Atlantic, somewhere between the latitudes of Lisbon and Oporto, ventured to account for what became of the water as the sea-level and he estimated that the depth at which it originated could not subsided, though, in despite of their antipathy to anything like be much less than I m., and probably did not exceed 3 m. Michell, speculation, they could not help suggesting, as an answer to the however, misconceived the character of the waves which he described, cogent arguments of their opponents,

at “one of

celestial seeing that he believed them to be due to the actual propagation of bodies which sometimes approach near to the earth may have been the vapour itsell underneath the surface of the earth. 'A century able to withdraw a portion of our atmosphere and of our ocean." had almost passed after the date of his essay before modern scientific Nor was any attempt made to explain the extraordinary nature of methods of observation and the use of recording instruments began the supposed chemical precipitates of the universal ocean. The to be applied to the study of earthquake phenomena. In 1846 Robert progress of inquiry even in Werner's lifetime disproved some of Mallet (1810-1881) published an important paper “On the Dynamics the fundamental portions of his system. Many of the chemical of Earthquakes " in the Transactions of the Royal Irish Academy. precipitates were shown to be masses that had been erupted in a From that time onward he continued to devote his energies to the molten state from below. His order of succession was found not investigation, studying the effects of the Calabrian earthquake of to hold good; and though he tried to readjust his sequence and to 1857, experimenting on the transmission of waves of shock through introduce into it modifications to suit new facts, its inherent arti. various materials, caused by exploding charges of gunpowder, and ficiality led to its speedy decline after his death. It must be concollecting all the information to be obtained on the subject. His ceded, however, that the stress which he laid upon the fact that the writings, and especially his work in two volumes on The First rocks of the earth's crust were deposited in a definite order had an Principles of Observational Seismology, must be regarded as having important influence in directing attention to this subject, and in laid the foundations of this branch of modern geology (see EARTH. preparing the way for a more natural system, based not on mere QUAKE; SEISMOMETER).

mineralogical characters, but having regard to the organic remains, History of the Evolution of Stratigraphical Geology:-Men had long which were now being gathered in ever-increasing numbers and been familiar with the evidence that the present dry land once lay variety from stratified formations of many different ages and from under the sea, before they began to realize that the rocks, of which all parts of the globe. the land consists, contain a record of many alternations of land and It was in France and in England that the foundations of strati. sea, and relics of a long succession of plants and animals from carly graphy, based upon a knowledge of organic remains, were first and simple types up to the manifold and complex forms of to-day. successfully laid. Abbé J. L. Giraud-Soulavie (1752-1813), in his In countries where coal-mining had been prosecuted for generations, Histoire naturelle de la France méridionale, which appeared in seven it had been recognized that the rocks consist of strata superposed volumes, subdivided the limestones of Vivarais into five ages, each on each other in a definite order, which was found to extend over marked by a distinct assemblage of shells. In the lowest strata, the whole of a district. As far back as 1719 John Strachey drew representing the first age, none of the fossils were believed by him attention to this fact in a communication published in the Philoso- to have any living representatives, and he called these rocks“ Primphical Transactions. John Michell (1760), in the paper on earth- ordial." In the next group a mingling of living with extinct forms quakes already cited, showed that he had acquired a clear under. was observable. The third age was marked by the presence of standing of the order of succession among stratified formations, and shells of still existing species. The strata of the fourth series were perceived that to disturbances of the terrestrial crust must be ascribed characterized by carbonaceous shales or slates, containing remains the fact that the lower or older and more inclined strata form the of primordial vegetation, and perhaps equivalents of the first three mountains, while the younger and more horizontal strata are spread calcareous series. The fifth age was marked by recent deposits over the plains.

containing remains of terrestrial vegetation and of land animals. In Italy G. Arduino (1713-1795) classified the rocks in the north It is remarkable that these sagacious conclusions should have been of the peninsula as Primitive, Secondary, Tertiary and Volcanic. formed and published at a time when the geologists of the Continent A similar threefold order was announced for the Harz and Erzgebirge were engaged in the controversy about the origin of basalt, or in by J. G. Lehmann in 1756. He recognized in that region an ancient disputes about the character and stratigraphical position of the series of rocks in inclined or vertical strata, which rise to the tops supposed universal formations, and when the interest and

importance of the hills and descend to an unknown depth into the interior. of fossil organic remains still remained unrecognized by the vast These masses, he thought, were contemporaneous with the making majority of the combatants. of the world. Next came the Flötzgebirge, consisting of younger The rocks of the Paris basin display so clearly an orderly sediments, disposed in flat or gently inclined sheets which overlie arrangement, and are so distinguished for the variety and perfect preservation of their enclosed organic remains, that they could not out and application of the principle of zonal classification to the fail to attract the early notice of observers. J. E. Guettard, G. F. lossiliferous formations that is, the determination of the sequence Rouelle (1703-1770), N. Desmarest, A. L. Lavoisier (1743-1794) and distribution of organic remains in these formations, and the and others made observations in this interesting district. But it arrangement of the strata into zones, each of which is distinguished was reserved for Cuvier (1769-1832) and A. Brongniart (1770-1847) by a peculiar assemblage of fossil species (see under Part VI.). The to work out the detailed succession of the Tertiary formations, and zones are usually named after one especially characteristic species to show how each of these is characterized by its own peculiar | This system of classification was begun in Germany with reference assemblage of organic remains. The later progress of investigation to the members of the Jurassic system (9.v.) by A. Oppel (1856-1858) has slightly corrected and greatly amplified the tabular arrangement and F. A. von Quenstedt (1858), and it has since been extended established by these authors in 1808, but the broad outlines of the through the other Mesozoic formations. It has even been found to Tertiary stratigraphy of the Paris basin remain still as Cuvier and be applicable to the Palaeozoic rocks, which are now subdivided Brongniart left them. The most important subsequent change into palaeontological zones. In the Silurian system, for example, the in the classification of the Tertiary formations was made by Sir graptolites have been shown by c. Lapworth to furnish a useful Charles Lyell, who, conceiving in 1828 the idea of a classification basis for zonal subdivisions. The lowest fossiliferous horizon in the of these rocks by reference to their relative proportions of living Cambrian rocks of Europe and North America is known as the and extinct species of shells, established, in collaboration with Olenellus zone, from the prominence in it of that genus of trilobite. G. P. Deshayes, the now universally accepted divisions Eocene, Another conspicuous feature in the progress of stratigraphy Miocene and Pliocene.

during the second half of the 19th century was displayed by the rise Long before Cuvier and Brongniart published an account of their and rapid development of what is known as Glacial geology. The researches, another observer had been at work among the Secondary various deposits of " drift" spread over northern Europe, and the formations of the west of England, and had independently dis- boulders scattered across the surface of the plains had long attracted covered that the component members of these formations were each notice, and had even found a place in popular legend and superstidistinguished by a peculiar group of organic remains; and that this tion. When men began to examine them with a view to ascertain distinction could be used to discriminate them over all the region their origin, they were naturally regarded as evidences of the through which he had traced them. The remarkable man who Noachian deluge. The first observer who drew attention to the arrived at this far-reaching generalization was William Smith (1769- smoothed and striated surfaces of rock that underlie the Drifts was 1839), a land surveyor who, in the prosecution of his professional Hutton's

friend, Sir James Hall, who studied them in the lowlands business, found opportunities of traversing a great part of England, of Scotland and referred them to the action of great debacles of and of putting his deductions to the test. As the result of these water, which, in the course of some ancient terrestrial convulsion, journeys he accumulated materials enoug to enable him to produce had been launched across the face of the country. Playfair, however, á geological map of the country, on which the distribution and pointed out that the most potent geological agents for the transsuccession of the rocks were for the first time delineated. Smith's portation of large blocks of stone are the glaciers. But no one was labours laid the foundation of stratigraphical geology in England then bold enough to connect the travelled boulders with glaciers and he was styled even in his lifetime the "Father of English on the plains of Germany and of Britain. Yet the transporting geology." From his day onward the significance of fossil organic agency of ice was invoked in explanation of their diffusion. It remains gained rapidly increasing recognition. Thus in England came to be the prevalent belief among the geologists of the first the outlines traced by him among the Secondary and Tertiary half of the 19th century, that the fall of temperature, indicated by formations were admirably filled in by Thomas Webster (1773-1844); the gradual increase in the number of northern species of shells while the Cretaceous series was worked out in still greater detail in the English Crag deposits, reached its climax during the time in the classic memoirs of William Henry Fitton (1780-1861). of the Drift, and that much of the north and centre of Europe was

There was one stratigraphical domain, however, into which William then submerged beneath a sea, across which floating icebergs and Smith did not enter. He traced his sequence of rocks down into the focs transported the materials of the Drift and dropped the scattered Coal Measures, but contented himself with only a vague reference boulders. As the phenomena are well developed around the Alps, to what lay underneath that formation. Though some of these it was necessary to suppose that the submergence involved the underlying rocks had in various countries yielded abundant fossils, lowlands of the Continent up to the foot of that mountain chain they had generally suffered so much from terrestrial disturbances, a geographical change so stupendous as to demand much more and their order of succession was consequently often so much evidence than was adduced in its support. At last Louis Agassiz obscured throughout western Europe, that they remained but little (1807-1873), who had varied his palacontological studies at Neuchâtel known for many years after the stratigraphy of the Secondary and by excursions into the Alps, was so much struck by the proofs of Tertiary series had been established. At last in 1831 Murchison the former far greater extension of the Swiss glaciers, that he pursued began to attack this terra incognita on the borders of South Wales, the investigation and satisfied himself that the ice had formerly working into it from the Old Red Sandstone, the stratigraphical extended from the Alpine valleys right across the great plain of position of which was well known. In a few years he succeeded in Switzerland, and had transported huge boulders from the central demonstrating the existence of a succession of formations, each mountains to the flanks of the Jura. In the year 1840 he visited distinguished by its own peculiar assemblage of organic remains Britain and soon found evidence of similar conditions there. He which were distinct from those in any of the overlying strata. To showed that it was not by submergence in a sca cumbered with these formations he gave the name of Silurian (9.v.). From the floating ice, but by the former presence of vast glaciers or sheets of key which his researches supplied, it was possible to recognize in ice that the Drift and erratic blocks had been distributed. The idea other countries the same order of formations and the same sequence thus propounded by him did not at oncecommand complete approval, of fossils, so that, in the course of a few years, representatives of the though traces of ancient glaciers in Scotland and Wales were soon Silurian system were found far and wide over the globe. While detected by native geologists, particularly by W. Buckland, Lyell, Murchison was thus engaged, Sedgwick devoted himself to the more J. D. Forbes and Charles Maclaren. Robert Chambers

(1802-1671) difficult task of unravelling the complicated structure of North did good service in gathering additional evidence from Scotland and Wales. He eventually made out the order of the several formations Norway in favour of Agassiz's views, which steadily gained adherents there, with their vast intercalations of volcanic material. He named until, after some quarter of a century, they were adopted by the them the Cambrian system (q.v.), and found them to contain fossils, great majority of geologists in Britain, and subsequently in other which, however, lay for some time unexamined by him. He at countries. Since that time the literature of geology has been swollen first believed, as Murchison also did, that his rocks were all older by a vast number of contributions in which the history of the Glacial than any part of the Silurian series. It was eventually discovered period, and its records both in the Old and New World, have been that a portion of them was equivalent to the lower part of that fully discussed. series. The oldest of Sedgwick's groups, containing distinctive Rise and Progress of Palocontological Geology.-As this branch of fossils, retain the name Cambrian, and are of high interest, as they the science deals with the evidence furnished by fossil organic enclose the remains of the earliest faunas which are yet well known. remains as to former geographical conditions, it early attracted Sedgwick and Murchison rendered yet another signal service to observers who, in the superficial beds of marine shells found at some stratigraphical geology by establishing, in 1839, on a basis of distance from the coast, saw proofs of the former submergence of palaeontological evidence supplied by W. Lonsdale, the independence the land under the sea. But the occurrence of fossils embedded in of the Devonian system (9.0.)

the heart of the solid rocks of the mountains offered much greater For many years the rocks below the oldest fossiliferous deposits difficulties of explanation, and further progress was consequently received comparatively little attention. They were vaguely described slow. Especially banesul was the belief that these objects were as the “crystalline schists" and were often referred to as parts of mere sports of nature, and had no connexion with any once living the primeval crust in which no chronology was to be looked for. organisms. So long as the true organic origin of the fossil plants and W. E. Logan (1798-1875) led the way, in Canada, by establishing animals contained in the rocks was in dispute, it was hardly possible there several vast series of rocks, partly of crystalline schists and that much advance could be made in their systematic study, or in gneisses (Laurentian) and partly of slates and conglomerates the geological deductions to be drawn from them. One good result (Huronian). Later observers, both in Canada and the United of the controversy, however, was to be seen in the large collections States, have greatly increased our knowledge of these rocks, and of these "formed stones" that were gathered together in the cabinets have shown their structure to be much more complex than was at and museums of the 17th and 18th centuries. The accumulation first supposed (see ARCHEAN SYSTEM).

and comparison of these objects naturally led to the production of During the latter half

of the 19th century the most important treatises in which they were described and not unfrequently illus. development of stratigraphical geology was the detailed working trated by good engravings. Switzerland was more particularly

noted for the number and merit of its works of this kind, such as that | into existence. When rocks began to be more particularly scrutinof K. N. Lang (Historio lapidum figuratorum Helvetiae, 1708) and ized, it was chiefly from the side of their usefulness for building those of Johann Jacob Scheuchzer (1672-1733). In England, also, and other economic purposes. The occurrence of marine shells in illustrated treatises were published both by men who looked on many of them had early attracted attention to them. But their fossils as mere freaks of nature, and by those who regarded them as varieties of composition and origin did not become the subject of proofs of Noah's flood. Of the former type were the works of Martin serious study until after Linnaeus and J. G. Wallerius in the 18th Lister (1638-1712) and Robert Plot (Natural History of Oxfordshire, century had made a beginning. The first important contribution 1677). The Celtic scholar Edward Llwyd (1660-1709) wrote a Latin to this department of the science was that of Werner, who in 1786 Museum, Oxford, and plates of a thousand fossils in the Ashmoleanpublished a classification and description of rocks in which he

Woodward, in 1728-1729, published his arranged them in two divisions, simple and compound, and further Natural History of the Fossils of England, already mentioned, wherein distinguished them by various external characters and by their he described his own extensive collection, which he bequeathed to relative age. The publication of this scheme may be said to mark the University of Cambridge, where it is still carefully preserved. the beginning of scientific petrography. Werner's system, however, The most voluminous and important of all these works, however, had the serious defect that the chronological order in which he appeared at a later date at Nuremberg. It was begun by G. W grouped the rocks, and the hypothesis by which he accounted for Knorr (1705-1761), who himself engraved for it a series of plates, them as chemical precipitates from the original ocean, were both which for beauty and accuracy have seldom been surpassed. After alike contrary to nature. It was hardly possible indeed that much his death the work was continued by J. E. 1. Walch (1725-1778), and progress could be made in this branch of geology until chemistry ultimately consisted of four massive folio volumes and nearly 300 and mineralogy had made greater advances; and especially until plates under the title of Lapides diluvii universalis testes. Although it was possible to ascertain the intimate chemical and mineralogical the authors supposed their fossils to be relics of Noah's flood, their composition, and the minute structure of rocks. The study, however, work must be acknowledged to mark a distinct onward stage in the continued

to be pursued in Germany, where the influence of Werner's palaeontological department of geology.

enthusiasm still led men to enter the petrographical rather than the It was in France that palaeontological geology began to be culti palaeontological domain. The resources of modern chemistry were vated in a scientific spirit. The potter Bernard Palissy, as far back pressed into the service, and analyses were made and multiplied to as 1580, had dwelt on the importance of fossil shells as monuments such a degree that it seemed as if the ultimate chemical constitution of revolutions of the earth's surface; but the observer who first of every type of rock had now been thoroughly revealed. The undertook the detailed study of the subject was Jean Etienne condition of the science in the middle of the 19th century was well Guettard, who began in 1751 to publish his descriptions of fossils shown by J. L. A. Roth, who in 1861 collected about 1000 trust. in the form of memoirs presented to the Academy of Sciences of worthy analyses which up to that time had been made. But though Paris. To him they were not only of deep interest as monuments the chemical elements of the rocks had been fairly well determined, of former types of cxistence, but they had an especial value as the manner in which they were combined in the compound rocks records of the changes which the country had undergone from sea could for the most part bé only more or less plausibly conjectured. to land and from land to sca. More especially noteworthy was a As far back as 1831 an account was published of a process devised by monograph by him which appeared in 1765 bearing the title "On William Nicol of Edinburgh, whereby sections of fossil wood could be the accidents that have befallen Fossil Shells compared with those cut, mounted on glass, and reduced to such a degree of transparency which are found to happen to shells now living in the Sea." In this as to be easily examined under a microscope. Henry Sorby, of treatise he showed that the fossils have been encrusted with barnacles Sheffield, having seen Nicol's preparations, perceived how admirably and serpulae, have been bored into by other organisms, and have adapted the process was for the study of the minute structure and often been rounded or broken before final entombment; and he composition of rocks. In 1858 he published in the Quarterly Journal inferred that these fossils must have lived and died on the sea-floor of the Geological Society a paper “On the Microscopical Structure of under similar conditions to those which obtain on the sea-floor Crystals." This essay led to a complete revolution of petrographical to-day. His argument was the most triumphant that had ever methods and gave a vast impetus to the study of rocks. Petrology been brought against the doctrine of lusus nalurae, and that of the entered upon a new and wider field of investigation. Not only were efficacy of Noah's flood doctrines which still held their ground in the mineralogical constituents of the rocks detected, but minute Guettard's day. When Soulavie, Cuvier and Brongniart in France, structures were revealed which shed new light on the origin and and William Smith in England, showed that the rock formations history. of these mineral masses, and opened up new paths in of the earth's crust could be arranged in chronological order, and theoretical geology. In the hands of H. Vogelsang, F. Zirkel, could be recognized far and wide by means of their enclosed organic H. Rosenbusch, and a host of other workers in all civilized countries, remains, the vast significance of these remains in gcological rescarch the literature of this department of the science has grown to a was speedily realized, and palaeontological geology at once entered remarkable extent. . Armed with the powerful aid of modern optical on a new and enlarged phase of development. But apart from instruments, geologists are now able with far more prospect of success their value as chronological monuments, and as witnesses of former to resume the experiments begun a century before by de Saussure conditions of geography, fossils presented in themselves a wide and Hall. . G. A. Daubrée, C. Friedel, E. Sarasin, F. Fouqué and field of investigation as types of life that had formerly existed, but A. Michel Lévy in France, C. Doelter y Cisterich and E. Hussak of had now passed away. It was in France that this subject first took Gratz, J. Morozewicz of Warsaw and others, have greatly advanced definite shap. as an important branch of science. The mollusca of our knowledge by their synthetical analyses, and there is every the Tertiary deposits of the Paris basin became, in the hands of reason to hope that further advances will be made in this field of Lamarck, the basis on which invertebratc palacontology was founded. research. The same series of strata furnished to Cuvier the remains of extinct Rise of Physiographical Geology:-Until stratigraphical geology land animals, of which, by critical study of their fragmentary bones had advanced so far as to show of what a vast succession of rocks the and skeletons, he worked out restorations that may be looked on crust of the earth is built up, by what a long and complicated series as the starting point of vertebrate palacontology. These brilliant of revolutions these rocks have come to assume their present positions, researches, rousing widespread interest in such studies, showed how and how enormous has been the lapse of time which all these changes great a flood of light could be thrown on the past history of the earth represent, it was not possible to make a scientific study of the surface and its inhabitants. But the full significance of these extinct types features of our globe. From ancient times it had been known that of life could not be understood so long as the doctrine of the immuta- many parts of the land had once been under the sea; but down even bility of species, so strenuously upheld by Cuvier, maintained its to the beginning of the 19th century the vaguest conceptions consway among naturalists. Lamarck, as far back as the year 1800, tinued to prevail as to the operations concerned in the submergence had begun to propound his theory of evolution and the transforma and elevation of land, and as to the processes whereby the present tion of species; but his views, strongly opposed by Cuvier and the outlines of terrestrial topography were determined. We have seen, great body of naturalists of the day, fell into neglect. Not until for instance, that according to the teaching of Werner the oldest after the publication in 1859 of the Origin of Species by Charles rocks were first precipitated from solution in the universal ocean to Darwin were the barricrs of old prejudice in this matter finally form the mountains, that the vertical position of their strata was broken down. The possibility of tracing the ancestry of living forms original, that as the waters subsided successive formations were back into the remotest ages was then perceived: the time-honoured deposited and laid bare, and that finally the superfluous portion of the fiction that the stratified formations record a series of catastrophes ocean was whisked away into space by some unexplained co-operation and re-creations was finally dissipated; and the earth's crust was of another planetary body. Desmarest, in his investigation of the seen to contain a noble, though imperfect, record of the grand volcanic history of Auvergne, was the first observer to perceive by evolution of organic types of which our planet has been the theatre. what a long process of sculpture the present configuration of the land

Development of Petrographical Geology-Theophrastus, the favour- has been brought about. Heshowed conclusively that the valleys have ite pupil of Aristotle, wrote a treatise On Slones, which has come been carved out by the streams that flow in them, and that while down to our own day, and may be regarded as the earliest work on they have sunk deeper and deeper into the framework of the land, petrography. At a subsequent period Pliny, in his Natural History, the spaces of ground between them have been left as intervening collected all that was known in his day regarding the occurrence ridges and hills. De Saussure learnt a similar lesson from his studies and uses of minerals and rocks. But neither of these works is of the Alps, and Hutton and Playfair made it a cardinal feature in of great scientific importance, though containing much interesting their theory of the earth. Nevertheless the idea encountered so information. Minerals from their beauty and value attracted much opposition that it made but little way until after the middle notice before much attention was paid to rocks, and their study of the 19th century. Geologists preferred to believe in convulgave rise to the science of mineralogy long before geology came' sions of nature, whereby valleys were opened and mountains were

« PreviousContinue »