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more numerous, complex, variable and practically important: oldest lying at the bottom and the newest at the top. Relics From the underlying abstract mathematical considerations all
of an ancient sea-floor are overlain by traces of a vanished Con
through the superimposed physical, biological, anthropoclusioa.
logical. political and commercial development of the land-surface; these are in turn covered by the deposits of a
subject runs the determining control exercised by crust. former lake, above which once more appear proofs of the return forms acting directly or indirectly on mobile distributions;
and this of the sea. Among these rocky records lie the lavas and ashes is the essential principle of geography.
(H. R. M.)
of long-extinct volcanoes. The ripple left upon the shore, the GEOID (from Gr. r, the earth), an imaginary surface em- cracks formed by the sun's heat upon the muddy bottom of a ployed by geodesists which has the property that every element dried-up pool, the very imprint of the drops of a passing rainof it is perpendicular to the plumb-line where that line cuts it. shower, have all been accurately prescrved, and yield their Compared with the “ spheroid of reference " the surface of the evidence as to geographical conditions often widely different geoid is in general depressed over the oceans and raised over from those which exist where such markings are now found. the great land masses. (Sce EARTH, FIGURE OF THE.)
But it is mainly by the remains of plants and animals imbedded GEOK-TEPE, a former fortress of the Turkomans, in Russian in the rocks that the geologist is guided in unravelling the Transcaspia, in the oasis of Akhal-tekke, on the Transcaspian chronological succession of geological changes. He has found railway, 28 m. N.W. of Askabad. It consisted of a walled that a certain order of appearance characterizes these organic enclosure ifm. in circuit, the wall being 18 ft. high and 20 to remains, that each great group of rocks is marked by its own 30 ft, thick. In December 1880 the place was attacked by special types of life, and that these types can be recognized, 6000 Russians under General Skobelev, and after a siege of and the rocks in which they occur can be correlated even in twenty-three days was carried by storm, although the defenders distant countries, and where no other means of comparison numbered 25,000.
A monument and a small museum com- would be possible. At one moment he has to deal with the bones memorate the event.
of some large mammal scattered through a deposit of superficial GEOLOGY (from Gr. vñ, the earth, and Loyos, science), the gravel,at another time with the minute foraminifers and ostracods science which investigates the physical history of the earth. of an upraised sca-bottom. Corals and crinoids crowded and Its object is to trace the structural progress of our planet from crushed into a massive limestone where they lived and died, the earliest beginnings of its separate existence, through its ferns and terrestrial plants matted together into a bed of coal various stages of growth, down to the present condition of where they originally grew, the scattered shells of a submarine things. It seeks to determine the manner in which the evolution sand-bank, the snails and lizards which lived and died within of the earth's great surface features has been effected. It un- a hollow-tree, the insects which have been imprisoned within ravels the complicated processes by which each continent has the exuding resin of old forests, the footprints of birds and been built up. It follows, even into detail, the varied sculpture quadrupeds, the trails of worms left upon former shores-these, of mountain and valley, crag and ravine. Nor does it confine and innumerable other picces of evidence, enable the geologist itself merely to changes in the inorganic world. Geology shows to realize in some measure what the faunas and foras of successivo that the present races of plants and animals are the descendants periods have been, and what geographical changes the site of of other and very different races which once peopled the earth. every land has undergone. It teaches that there has been a progressive development of the It' is evident that to deal successfully with these varied inhabitants, as well as one of the globe on which they have materials, a considerable acquaintance with different branches dwelt; that each successive period in the earth's history, since of science is needful. Especially necessary is a tolerably wide the introduction of living things, has been marked by character- knowledge of the processes now at work in changing the surface istic types of the animal and vegetable kingdoms; and that, of the earth, and of at least those forms of plant and animal however imperfectly the remains of these organisms have been life whose remains are apt to be preserved in geological deposits, preserved or may be deciphered, materials exist for a history or which in their structure and habitat enable us to realize what of life upon the planet. The geographical distribution of existing their forerunners were. It has often been insisted that the saunas and floras is often made clear and intelligible by geological present is the key to the past; and in a wide sense this assertion evidence; and in the same way light is thrown upon some of is eminently true. Only in proportion as we understand the the remoter phases in the history of man himself. A subject present, where everything is open on all sides to the fullest investiso comprehensive as this must require a wide and varied basis gation, can we expect to decipher the past, where so much is of evidence. It is one of the characteristics of geology to gather obscure, imperfecily preserved or not preserved at all. A evidence from sources which at first sight seem far removed study of the existing economy of nature ought thus to be the from its scope, and to seek aid from almost every other leading foundation of the geologist's training. branch of science. Thus, in dealing with the earliest conditions While, however, the present condition of things is thus cmof the planet, the geologist must fully avail himself of the ployed, we must obviously be on our guard against the danger labours of the astronomer. Whatever is ascertainable by of unconsciously assuming that the phase of nature's operations telescope, spectroscope or chemical analysis, regarding the con- which we now witness has been the same in all past time, that stitution of other heavenly bodies, has a geological bearing. geological changes have always or generally taken place in former The experiments of the physicist, undertaken to determine ages in the manner and on the scale which we behold to-day, conditions of matter and of energy, may sometimes be taken and that at the present time all the great geological processes
, as the starting-points of geological investigation. The work which have produced changes in the past eras of the earth's of the chemical laboratory forms the foundation of a vast and history, are still existent and active. As a working hypothesis increasing mass of geological inquiry. To the botanist, the we may suppose that the nature of geological processes has zoologist, even to the unscientific, if observant, traveller by land remained constant from the beginning; but we cannot postulate or sea, the geologist turns for information and assistance. that the action of these processes has never varied in energy.
But while thus culling freely from the dominions of other | The few centuries wherein man has been observing nature sciences, geology claims as its peculiar territory the rocky obviously form much too brief an interval by which to measure framework of the globe. In the materials composing that the intensity of geological action in all past time. For aught framework, their composition and arrangement, the processes we can tell the present is an era of quietude and slow change, of their formation, the changes which they have undergone, compared with some of the eras which have preceded it. Nor and the terrestrial revolutions to which they bear witness, lie perhaps can we be quite sure that, when we have explored the main data of geological history. It is the task of the geologist every geological process now in progress, we have exhausted to group these elements in such a way that they may be made all the causes of change which, even in comparatively recent to yield up their evidence as to the march of events in the times, have been at work. evolution of the planet. He finds that they have in large In dealing with the geological record, as the accessible solid measure arranged themselves in chronological sequence, the part of the globe is called, we cannot too vividly realize that at
the best it forms but an imperfect chronicle. Geological history | geological history. It works out the chronological succession cannot be compiled from a full and continuous series of docu- of the great formations of the earth's crust, and endeavours to ments. From the very nature of its origin the record is necessarily trace the sequence of events of which they contain the record. fragmentary, and it has been further mutilated and obscured More particularly, it determines the order of succession of the by the revolutions of successive ages. And even where the various plants and animals which in past time have peopled chronicle of events is continuous, it is of very unequal value in the earth, and thus ascertains what has been the grand march different places. In one case, for example, it may present us of life upon this planet. with an unbroken succession of deposits many thousands of 8. Physiographical Geology, proceeding from the basis of feet in thickness, from which, however, only a few meagre facts fact laid down by stratigraphical geology regarding former as to geological history can be gleaned. In another instance geographical changes, embraces an inquiry into the origin and it brings before us, within the compass of a few yards, the history of the features of the earth's surface continental ridges evidence of a most varied and complicated series of changes and ocean basias, plains, valleys and mountains. It explains in physical geography, as well as an abundant and interesting the causes on which local differences of scenery depend, and suite of organic remains. These and other characteristics of shows under what very different circumstances, and at what the geological record become more apparent and intelligible as widely separated intervals, the hills and mountains, even of a we proceed in the study of the science.
single country, have been produced. Classification.-For systematic treatment the subject may be Most of the detail embraced in these several sections is conveniently arranged in the following parts:
relegated to separate articles, to which references are here 1. The Historical Development of Geological Science.-Here inserted. The following pages thus deal mainly with the general a brief outline will be given of the gradual growth of geological principles and historical development of the science:conceptions from the days of the Greeks and Romans down to modern times, tracing the separate progress of the more important
PART I.-HISTORICAL DEVELOPMENT branches of inquiry and noting some of the stages which in each Geological Ideas among the Greeks and Romans.-Many geological case have led up.to the present condition of the science.
phenomena present themselves in so striking a form that they could 2. The Cesmical Aspects of Geology. This section embraces hardly fail to impress the imagination of the earliest and rudest the evidence supplied by astronomy and physics regarding the eruptions, destructive storms on land and sea, disastrous floods and form and motions of the earth, the composition of the planets landslips suddenly strewing valleys with ruin, must have awakened and sun, and the probable history of the solar system. The the terror of those who witnessed them. Prominent features of subjects dealt with under this head are chiefly treated in separate thunderstorms, dark river-chasms that scem purposely cleft open in articles.
order to give passage to the torrents that rush through them, crags 3. Geognosy.-An inquiry into the materials of the earth's with their impressive array of pinnacles and recesses must have substance. This division, which deals with the parts of the appealed of old, as they still do, to the awe and wonder of those earth, its envelopes of air and water, its solid crust and the far inland districts would, in course of time, arrest the attention of probable condition of its interior, especially treats of the more the more intelligent and reflective observers, and raise in their minds important minerals of the crust, and the chief rocks of which some kind of surmise as to how such shells could ever have come that crust is built up. Geognosy thus lays a foundation of know there. These and other conspicuous, geological problems found ledge regarding the nature of the materials constituting the mass striking terrestrial features and the elemental forces of nature were
their earliest solution in legends and myths, wherein the more of the globe, and prepares the way for an investigation of the represented to be the manifestation of the power of unseen superprocesses by which these materials are produced and altered. natural beings.
4. Dynamical Geology studies the nature and working of the The basin of the Mediterranean Sea was especially well adapted, various geological processes whereby the rocks of the earth's from its physical conditions, to be the birth place of such fables: crust are formed and metamorphosed, and by which changes distinct centres of volcanic activity, one in the Aegean Sea and one
It is a region frequently shaken by earthquakes, and contains two are effected upon the distribution of sea and land, and upon in Italy. It is bounded on the north by a long succession of lofty the forms of terrestrial surfaces. Such an inquiry necessitates snow-capped mountain ranges, whence copious rivers, often swollen a careful examination of the existing geological economy of by heavy rains or melted snows, carry the drainage into the sea.
On the south it boasts the Nile, once so full of mystcry; likewise nature, and forms a fitting introduction to an inquiry into the wide tracts of arid desert with their dreaded dust storms. geological changes of former periods.
Mediterranean itself, though an inland sea, is subject to gales, 5. Geotectonic or Structural Geology has for its object the which, on exposed coasts, raise breakers quite large enough to give a
The countries that architecture of the earth's crust. It embraces an inquiry into the vivid impression of the power of ocean waves. manner in which the various materials composing this crust spread deposits full of sea shells, like those that still live in the
surround this great sheet of water display in many places widelyhave been arranged. It shows that some have been formed neighbouring bays and gulls. Such a region was not only well fitted in beds or strata of sediment on the floor of the sea, that others to supply subjects for mythology, but also to furnish, on every side, have been built up by the slow aggregation of organic forms, materials which, in their interest and suggestiveness, would appeal that others have been poured out in a molten condition or in to the reason of observant men.
It was natural, therefore, that the early philosophers of Greece showers of loose dust from subterranean sources. It further should have noted some of these geological features, and should have reveals that, though originally laid down in almost horizontal sought for other explanations of them than those to be found in the beds, the rocks have subsequently been crumpled, contorted popular myths. The opinions entertained in antiquity on these and dislocated, that they have been incessantly worn down, logical processes now in operation, and (2) geological changes in
subjects may be conveniently grouped under two heads: (1) Geoand have often been depressed and buried beneath later the past. accumulations.
1. Contemporary Processes.-The geological processes of the present 6. Palacontological Geology.-- This branch of the subject, time are partly at work underground and partly on the surface of the starting from the evidence supplied by the organic forms which earth. The former, from their frequently disastrous
Earthare found preserved in the crust of the earth, includes such Roman authors. Aristotle, in his Meteorics, cites the quakes and questions as the relations between extinct and living types, speculations of several of his predecessors which he rejects the laws which appear to have governed the distribution of life in favour of his own opinion to the effect that earthquakes are due in time and in space, the relative importance of different genera warmth of the sun and the internal heat. Wind,
being the lightest
to the generation of wind within the earth, under the influence of the of animals in geological inquiry, the nature and use of the and most rapidly moving body, is the cause of motion in other evidence. from organic remains regarding former conditions bodies, and fire, united with wind, becomes flame, which is endowed of physical geography. Some of these problems belong also to with great rapidity of motion. Aristotle looked upon earthquakes zoology and botany, and are more fully discussed in the articles discharge of hot materials to the surface being the result of a severe PALAEONTOLOGY and PALAEOBOTANY.
earthquake, when finally the wind rushes out with violence, and 7. Straligraphical Geology.--This section might be called sometimes buries the surrounding country under sparks and cinders,
as had happened at Lipari. These crude conceptions of the nature enormous duration, and because they are brought about so im. of volcanic action, and the cause of carthquakes, continued to prevail perceptibly that we fail to detect them in progress. In a celebrated for many centuries. They are repeated by Lucretius, who, however, passage in his Metamorphoses, Ovid puts into the mouth of the following Anaximenes, includes as one of the causes of earthquakes philosopher Pythagoras an account of what was probably regarded the fall of mountainous masses of rock undermined by time, and the as the Pythagorean view of the subject in the Augustan age. It consequent propagation of gigantic tremors far and wide through affirms the interchange of land and sea, the erosion of valleys by the earth. Strabo, having travelled through the volcanic districts descending rivers, the washing down of mountains into the sea, the of Italy, was able to recognize that Vesuvius had once been an disappearance of the rivers and the submergence of land by earthactive volcano, although no eruption had taken place from it within quake movements, the separation of some islands from, and the union human memory. He continued to hold the belief that volcanic of others with, the mainland, the uprise of hills by volcanic action, energy arose from the movement of subterranean wind. He believed the rise and extinction of burning mountains. There was a time that the district around the Strait of Messina, which had formerly before Etna began to glow, and the time is coming when the mountain suffered from destructive earthquakes, was seldom visited by them will cease to burn. after the volcanic vents of that region had been opened, so as to From this brief sketch it will be seen that while the ancients had provide an escape for the subterranean fire, wind, water and burning accumulated a good deal of information regarding the occurrence of masses. He cites in his Geography a number of examples of wide- geological changes, their interpretations of the phenomena were to spread as well as local sinkings of land, and alludes also to the uprise a considerable extent mere fanciful speculation. They had acquired of the sea-bottom. He likewise regards some islands as having been only a most imperfect conception of the nature and operation of the thrown up by volcanic agency, and others as torn from the mainland geological processes; and though many writers realized that the by such convulsions as earthquakes.
surface of the earth has not always been, and will not always remain, The most detailed account of earthquake phenomena which has as it is now, they had no glimpse of the vast succession of changes come down to us from antiquity is that of Seneca in his Quaestiones of that surface which have been revealed by geology. They built Naturales. This philosopher had been much interested in the hypotheses on the slenderest basis of fact, and did not realize the accounts given him by survivors and witnesses of the earthquake necessity of testing or verifying them. which convulsed the district of Naples in February A.D. 63. He Progress of Geological Conceptions in the Middle Ages. ---During the distinguished several distinct movements of the ground: ist, the centuries that succeeded the fall of the Western empire little progress up and down motion (succussio); 2nd, the oscillatory motion (in was made in natural science. The schoolmen in the snonasteries clinatio); and probably a third, that of trembling or vibration. and other seminaries were content to take their science from the While admitting that some earthquakes may arise from the collapse literature of Greece and Rome. The Arabs, however, not only of the walls of subterranean cavities, he adhered to the old idea, collected and translated that literature, but in some departments held by the most numerous and important previous writers, that made original observations themselves. To one of the most illustrious these commotions are caused mainly by the movements of wind of their number, Avicenna, the translator of Aristotle, a treatise has imprisoned within the earth. As to the origin of volcanic outbursts been ascribed, in which singularly modern ideas are expressed he supposed that the subterranean wind in struggling for an outlet, regarding mountains, some of which are there stated to have been and whirling through the chasms and passages, meets with great produced by an uplifting of the ground, while others have been left store of sulphur and other combustible substances, which by mere prominent, owing to the wearing a way of the softer rocks around friction are set on fire. The elder Pliny reiterates the commonly them. In either case, it is confessed that the process would demand accepted opinion as to the efficacy of wind underground. In long tracts of time for its completion. discussing the phenomena of earthquakes he remarks that towns After the revival of learning the ancient problem presented by with many culverts and houses with cellars suffer less than others, fossil shells imbedded in the rocks of the interior of many countries and that at Naples those houses are most shaken which stand on received renewed attention. But the conditions for its solution hard ground. It thus appears that with regard to subterranean were no longer what they had been in the days of the philosophers geological operations, no advance was made during the time of the of antiquity: Men were not now free to adopt and teach any docGreeks and Romans as to the theoretical explanation of these pheno-trine they pleased on the subject. The Christian church had meanmena; but a considerable body of facts was collected, especially while arisen to power all over Europe, and adjudged as heretics all as to the effects of earthquakes and the occurrence of volcanic who ventured to impugn any of her dogmas. She taught that the eruptions.
land and the sea had been separated on the third day of creation, The superficial processes of geology, being much less striking than before the appearance of any animal life, which was not created until those of subterranean energy, naturally attracted less attention in the fifth day. To assert that the dry land is made up in great part Action of antiquity. The operations of rivers, however, which so of rocks that were formed in the sea, and are crowded with the rivers.
intimately affect a human population, were watched with remains of animals, was plainly to impugn the veracity of the Bible.
more or less care. Herodotus, struck by the amount of Again, it had come to be the orthodox belief that only somewhere alluvial silt brought down annually by the Nile and spread over the about 6000 years had elapsed since the time of Adam and Eve. Nat inundated land, inferred that " Égypt is the gift of the river. If any thoughtful observer, impressed with the overwhelming force Aristotle, in discussing some of the features of rivers, displays con of the evidence that the fossiliferous formations of the earth's crust siderable acquaintance with the various drainage-systems on the must have taken long periods of time for their accumulation, vennorth side of the Mediterranean basin. He refers to the mountains tured to give public expression to his conviction, he ran considerable as condensers of the atmospheric moisture, and shows that the largest risk of being proceeded against as a heretic. It was needsul, there rivers rise among the loftiest high grounds. He shows how sensibly fore, to find some explanation of the facts of nature, which would not the alluvial deposits carried down to the sea increase the breadth run counter to the ecclesiastical system of the day. Various such of the land, and cites some parts of the shores of the Black Sea, interpretations were proposed, doubtless in an honest endeavour at where, in sixty years, the rivers had brought down such a quantity reconciliation. Three of these deserve special notice: (1) Many of material that the vessels then in use required to be of much able observers and diligent collectors of fossils persuaded themselves smaller draught than previously, the water shallowing so much that that these objects never belonged to organisms of any kind, but the marshy ground would, in course of time, become dry land. should be regarded as mere - freaks of nature," having no more Strabo supplies further interesting informati as to the work of connexion with any once living, creature than the frost patterns rivers in making their alluvia! plains and in pushing their deltas on a window. They were styled “formed or " figured stones. seaward. He remarks that these deltas are prevented from ad * lapides sui generis," and were asserted to be due to some inorganic vancing farther outward by the ebb and flow of the tides.
imitative process within the earth or to the influence of the stars. 2. Past Processes.--The abundant well-preserved marine shells (2) Observers who could not resist the evidence of their senses that exposed among the upraised Tertiary and post-Tertiary deposits in the fossil shells once belonged to living animals, and who, at the
the countries bordering the Mediterranean are not inOccur
same time, felt the necessity of accounting for the presence of marine frequently alluded to in Greek and Latin literature. organisms in the rocks of which the dry land is largely built up, rences of Xenophanes of Colophon (614 B.C.) noticed the occurrence sought a way out of the difficulty by invoking the Deluge of Noah. .
of shells and other marine productions inland among the Here was a catastrophe which, they said, extended over the wbole mountains, and inferred from them that the land had risen out of globe, and by which the entire dry land was submerged even up to the sea. A similar conclusion was drawn by Xanthus the Lydian the tops of the high hills. True, it only lasted one hundred and ifty (464 B.C.) from shells like scallops and cockles, which were found far days, but so little were the facts then appreciated that no difficulty from the sea in Armenia and Lower Phrygia. Herodotus, Eratos spems to have been generally felt in crowding the accumulation of thenes, Strato and Strabo noted the vast quantities of fossil shells in the thousands of leet of fossiliserous formations into that brief space different parts of Egypt, together with beds of salt, as evidence that of time. (3) Some more intelligent men in Italy, recognizing that the sea had once spread over the country. But by far the most these interpretations could not be upheld, fell back upon the idea philosophical opinions on the past mutations of the earth's surface that the rocks in which fossil shells
are imbedded might have been are those expressed by Aristotle in the treatise already cited. Re- heaped up by repeated and vigorous eruptions from volcanic centres. viewing the evidence of these changes, he recognized that the sea Certain modern eruptions in the Aegean Sea and in the Bay
of Naples now covers tracts that were once dry land, and that land will one had drawn attention to the rapidity with which hills of considerable day reappear where there is now sea. These alternations are to be size could be piled around an active crater. It was argued thali regarded as following each other in a certain order and periodicity. Monte Nuovo near Naples could have been accumulated to a height But they are apt to escape our notice because they require successive of nearly 500 ft. in two days, there seemed to be no reason against periods of time, which, compared with our brief existence, are of I believing that, during the time of the Flood, and in the course of the
centuries that have elapsed since that event, the whole of the fossili To the Italian school, as especially typihed in Steno, must be ferous rocks might have been deposited. Unfortunately for this assigned the honour of having thus begun to lay frmly and truly hypothesis it ignored the fact that these rocks do not consist of the first foundation stones of the modern science of volcanic materials.
geology. The same school included Antonio Vallisneri
Lazzaro So long as the fundamental question remained in dispute as to (1661-1730), who surpassed his predecessors in his wider
More. the true character and history of the stratified portion of the earth's and more exact knowledge of the fossiliserous rocks that form the crust containing organic remains, geology as a science could not backbone of the Italian peninsula, which he contended were formed begin its existence. The diluvialists (those who relied on the hy- during a wide and prolonged submergence of the region, altogether pothesis of the Flood) held the field during the 16th, 17th and a great different from the brief deluge of Noah. There was likewise Lazzaro part of the 18th century. They were looked on as the champions of Moro (1687-1740), who did good service against the diluvialists, orthodoxy; and, on that account, they doubtless wielded much but the fundamental feature of his system of nature lay in the more influence than would have been gained by them from the preponderant part which, unaware of the great difference between Iorce of their arguments. Yet during those ages there were not volcanic materials and ordinary sediment, he assigned to volcanic wanting occasional observers who did good service in combating the action in the production of the sedimentary rocks of the earth's prevalent misconceptions, and in preparing the way for the ultimate crust. He supposed that in the beginning the globe was completely triumph of truth. It was more especially in Italy, where many of surrounded with water, beneath which the solid earth lay as a smooth the more striking phenomena of geology are conspicuously
displayed, ball. On the third day
of creation, however, vast fires were kindled that the early pioneers of the science arose, and that for several inside the globe, whereby the smooth surface of stone was broken generations the most marked progress was made towards placing up, and portions of it, appearing above the water, formed the earliest the investigations of the past history of the earth upon a basis of land. From that time onward, volcanic eruptions succeeded each careful observation and scientific deduction. One of the first of other, not only on the emerged land, but on the sea-floor, over which Leonardo
these leaders was Leonardo da Vinci (1452-1519), who, the ejected material spread in an ever augmenting thickness of da Viad;
besides his achievements in painting, sculpture, archi- sedimentary strata. In this way Moro carried the history of the Fracas.
tecture and engineering, contributed some notable obser- stratified rocks beyond the time of the Flood back to the Creation, torto;
vations regarding the great problem of the origin of fossil which was supposed to have been some 1600 years earlier; and he Fallopplo.
shells. He ridiculed the notion that these objects could brought it down to the present day, when fresh sedimentary deposits
have been formed by the influence of the stars, and main are continually accumulating.. He thus incurred no censure from tained that they had once belonged to living organisms, and there the ecclesiastical guardians of the faith, and he succeeded in attract. fore that what is now land was formerly covered by the sea, ing increased public attention to the problems of geology. The Girolamo Fracastorio (1483-1553), claimed that the shells
could influence of his teaching, however, was subsequently in great part never have been left by the Flood, which was a mere temporary due to the Carmelite friar Generelli, who published an eloquent inundation, but that they proved the mountains, in which they exposition of Moro's views. occur, to have been successively uplifted out of the sea. On the The Cosmogonists and Theories of the Earth.-While in Italy other hand, even an accomplished anatomist like Gabriello Falloppio substantial progress was made in collecting information regarding (1523-1562) found it easier to believe that the bones of elephants, the fossiliserous formations of that country, and in forming conteeth of sharks, shells and other fossils were mere earthy inorganic clusions concerning them based upon more or less accurate observaconcretions, than that the waters of Noah's Flood could ever have tions, the tendency to mere fanciful speculation, which could not be reached as far as Italy.
wholly repressed in any country, reached a remarkable extravagance By much the most important member of this early band of Italian in England. In proportion as materials were yet lacking from writers was undoubtedly Nicolas Steno (1631-1687), who, though which to construct a history of the evolution of our planet in accordNicolas born in Copenhagen, ultimately settled in Florence. ance with the teaching of the church, imagination supplied the place Stero. Having made a European reputation as an anatomist, of ascertained fact, and there appeared during the last twenty years
his attention was drawn to gcological problems by finding of the 18th century a group of English cosmogonists, who, by the that the rocks of the north of Italy contained what appeared to be sensational character of their speculations, aroused general attention sharks' teeth closely resembling those of a dog-fish, of which he had both in Britain
and on the continent. It may be doubted, however, published the anatomy. Cautiously at first, for fear of offending whether the effect of their writings was not to hinder the advance orthodox opinions, but afterwards more boldly, he proclaimed his of true science by divert men from the observation of nature into conviction that those objects had once been part of living
animals, barren controversy over unrealities. It is not needful here to do and that they threw light on some of the past history of the earth. more than mention the names of Thomas Burnet, whose Sacred He published in 1669 a small tract, De solido intra solidum naturaliter Theory of the Earth appeared in 1681, and William Whiston, whose contento, in which he developed the ideas he had formed of this New Theory of the Earth was published in 1696. Hardly less fanciful history from an attentive study of the rocks. He showed that the than these writers, though his practical acquaintance with rocks stratified formations of the hills and valleys consist of such materials and fossils was infinitely greater, was John Woodward, whose as would be laid down in the form of sediment in turbid water; Essay lowards a Natural History of the Earth dates from 1695. More that where they contain marine productions this water is proved important as a contribution to science was the catalogue of the large to have been the sea; that diversities in their composition point to collection of fossils, which he had made from the rocks of England commingling of currents, carrying different kinds of sediment of and which he bequeathed to the university of Cambridge. This which the heaviest would first sink to the bottom. He made original catalogue appeared in 1728-1729 with the title of An attempt towards and important observations on stratification, and laid down some a Natural History of the Fossils of England. of the fundamental axioms in stratigraphy. He reasoned that as A striking contrast to these cosmogonists is furnished by another the original position of strata was approximately horizontal, when group, which arose in France and Germany, and gave to the world they are found to be steeply inclined or vertical, or bent into arches, the first rational ideas concerning the probable primeval
Descartes. they have been disrupted by subterranean exhalations, or by the evolution of our globe. The earliest of these pioneers was falling in of the roofs of underground cavernous spaces. It is to the illustrious philosopher René Descartes (1596-1650). He prothis alteration of the original position of the strata that the in-pounded a scheme of cosmical development in which he represented equalities of the earth's surface, such as mountains, are to be ascribed, the earth, like the other planets, to have been originally a mass of though some have been formed by the outburst of fire, ashes and glowing material like the sun, and to have gradually cooled on the stones from inside the earth. Another effect of the dislocation has outside, while still retaining an incandescent, self-luminous nucleus. been to provide fissures, which serve as outlets for springs. Steno's Yet with this noble conception, which modernt science has accepted, anatomical training peculiarly fitted him for dealing authoritatively Descartes could not shake himself free from the time-honoured with the question of the nature and origin of the fossils contained error in regard to the origin of volcanic action. He thought that in the rocks. He had no hesitation in affirming that, even if no shells certain exhalations within the earth condense into oil, which, when had ever been found living in the sea, the internal structure of these in violent motion, enters into the subterranean cavities, where it fossils would demonstrate that they once formed parts of living passes into a kind of smoke. This smoke is from time to time ignited animals. And not only shells, but teeth, bones and skeletons of by a spark of fire and, pressing, violently against its containing many kinds of fishes had been quarried out of the rocks, while some walls, gives rise to earthquakes. If the flame breaks through to the of the strata had skulls, horns and teeth of land-animals. Illustrating surface at the top of a mountain, it may escape with enormous his general principles by a sketch of what he supposed to have been energy, hurling forth much earth mingled with sulphur or bitumen, the past history of Tuscany, he added a series of diagrams which and thus producing a volcano. The mountain might burn for a show how clearly he had conceived the essential elements of strati- long time until at last its store of fuel in the shape of sulphur or graphy. He thought he could perceive the records of six successive bitumen would be exhausted. Not only did the philosopher refrain phases in the evolution of the framework of that country, and was from availing himself of the high internal temperature of the globe inclined to believe that a similar chronological sequence would be as the source of volcanic energy, he even did not make use of it as found all over the world. He anticipated the objections that would the cause of the ignition of his supposed internal fuel, but speculated be brought against his views on account of the insuperable difficulty on the kindling of the subterranean fires by the spirits or gases in granting the length of time that would be required for all the setting fire to the exhalations, or by the fall of masses of rock and geographical vicissitudes which his interpretation required. He the sparks produced by their friction or percussion. thought that many of the fossiis must be as old as the time of the The ideas of Descartes
evolution were enlarged general deluge, but he was careful not to indulge in any speculation and made more definite by Wilhelm Gottfried Leibnitz (1646-1716), as to the antiquity of the earth.
whose teaching has largely influenced all subsequent speculation
[HISTORICAL DEVELOPMENT on the subject. In his great tract, the Prologaea (published in 1749, he studied at Edinburgh and at Paris, and took his doctor's degree thirty-three years after his death), he traced the probable passage at Leiden. But having inherited a small landed property in
of our earth from an original condition of incandescent Berwickshire, he took to agriculture, and after putting
Huttoa, continuous cooling, acquired an external solid crust and rugose himself to Edinburgh, there to gratify the scientific surface. He thought that the more ancient rocks, such as granite tastes which he had developed early in life. He had been more and gneiss, might be portions of the earliest outer crust; and that as especially led to study minerals and rocks, and to meditate on the the external solidification advanced, immense subterranean cavities problems which they suggest as to the constitution and history of were left which were filled with air and water. By the collapse of the earth. His journeys in Britain and on the continent of Europe the roofs of these caverns, valleys might be originated at the surface, had furnished him with material for reflection; and he had graduwhile the solid intervening walls would remain in place and formally evolved a system or theory in which all the scattered facts mountains. By the disruption of the crust, enormous bodies of could be arranged so as to show their mutual dependence and their water were launched over the surface of the earth, which swept vast place in the orderly mechanism of the world. He used to discuss quantities of sediment together, and thus gave rise to sedimentary his views with one or two of his friends, but refrained from publishing deposits. After many vicissitudes of this kind, the terrestrial forces them to the world until, on the foundation of the Royal Society of calmed down, and a more stable condition of things was established. Edinburgh, he communicated an outline of his doctrine to that
An important feature in the cosmogony of Leibnitz is the learned body in 1785. Some years later he expanded this first essay prominent place which he assigned to organic remains in the stratified into a larger work in two volumes, which were published in 1795 rocks of the crust. Ridiculing the foolish attempts to account for with the title of Theory of the Earth, with Proofs and Illustrations. the presence of these objects by calling them "sports of nature, Hutton's teaching has exercised a profound influence on modern he showed that they are to be regarded as historical monuments; geology. This influence, however, has arisen less from his own and he adduced a number of instances wherein successive platforms writings than from the account of his doctrines given by
Joha of strata, containing organic remains, bear witness to a series of his friend John Playfair in the classic work entitled
Playfair. advances and retreats of the sea. He recognized that some of the Illustrations of the Hultonian Theory, published in 1802, fossils appeared to have nothing like them in the living world of Hutton wrote in so prolix and obscure a style as rather to repel than to-day, but some analogous forms might yet be found, he thought, attract readers. Playfair, on the other hand, expressed himself in in still unexplored parts of the earth; and even if no living repres such clear and graceful language as to command general attention, sentatives should ever be discovered, many types of animals might and to gain wide acceptance for his master's views. Unlike the have undergone transformation during the great changes which had older cosmogonists, Hutton refrained from trying to explain the affected the surface of the earth. In spite of his clear realization origin of things, and from speculations as to what might possibly of the vast store of potential energy residing within the highly heated have been the early
history of our globe. He determined from the interior of the earth, Leibnitz continued to regard volcanic action outset to interpret the past by what can be seen to be the present as due to the combustion of inflammable substances enclosed within order of nature; and he refused to admit the operation of causes the terrestrial crust, such as stone-coal, naphtha and sulphur. which cannot be shown to be part of the actual terrestrial system.
Appealing to a much wider public than Descartes or Leibnitz, and Like other observers who had preceded him, he recognized in the basing his speculations on a wider acquaintance with the organic various rocks composing the dry land evidence of former geographical Buffon.
and inorganic realms of nature, G. L. L. de Buffon (1707-conditions very different from those which now prevail. He saw
1788) was undoubtedly one of the most influential forces that the vast majority of rocks consist of hardened sediments and that in Europe guided the growth of geological ideas during the must have been deposited in the sea. He could distinguish among 18th century. He published in 1749 a Theory of the Earth, in which them an older or Primary series, and a younger or Secondary series; he adopted views similar to those of Descartes and Leibnitz as to and did not dispute the existence of a Tertiary series claimed by planetary evolution; but though he realized the importance of Peter Simon Pallas (1741-1811). He believed that these various fossils as records of former conditions of the earth's surface, he aqueous accumulations had been consolidated by subterranean heat, accounted for them by supposing that they had been deposited from that the oldest and lowest rocks had suffered most from this action, a universal ocean, a large part of which had subsequently been that into these more deep-seated masses subsequent veins and engulfed into caverns in the interior of the globe. Thirty years larger bodies of molten matter were injected from below, and thus later, after having laboured with skill and enthusiasm in all branches that what was originally loose detritus eventually became changed of natural history, he published another work, his famous Époques in such crystalline schists as are now found in mountain-chains. de la nature (1778), which is specially remarkable as the first attempt In the course of these terrestrial revolutions sedimentary strata, to deal with the history of the earth in a chronological manner, and originally more or less nearly horizontal, have been pushed upward, to compute, on a basis of experiment, the antiquity of the several dislocated, crumpled, placed on end, and even elevated to form stages of this history. His experiments were made with globes of ranges of lofty mountains. Hutton looked upon these disturbances cast iron, and could not have yielded results of any value for his as due to the expansive power of subterranean heat; but he did not purpose; but in so far as his calculations were not mere random attempt to sketch the mechanism of the process, and he expressly guesses but had some kind of foundation on experiment, they declined to offer any conjecture as to how the land so elevated deserve respectful recognition. He divided the history of our earth remains in that position. He thought that the interior of our into six periods of unequal duration, the whole comprising a period planet may“ be a fluid mass, melted,
but unchanged by the action of some 70,000 or 75,000 years. He supposed that the stage of of heat "; and, far from connecting volcanoes with the combustion of incandescence, before the globe had consolidated to the centre. inflammable substances, as had been the prevalent belief for so many lasted 2936 years, and that about 35,000 years elapsed before the centuries, he looked upon them as a beneficent provision of "spiracles surface had cooled sufficiently to be touched, and therefore to be to the subterranean furnace, in order to prevent the unnecessary capable of supporting living things. Terrestrial animal life, however, elevation of land and fatal effects of earthquakes." was not introduced until 55,000 or 60,000 years after the beginning A distinguishing feature of the Huttonian philosophy is to be of the world or about 15,000 years before our time. Looking into seen in the breadth of its conceptions regarding the geological the future, he foresaw that, by continued refrigeration, our globe operations continually in progress on the surface of the globe. will eventually become colder than ice, and this fair face of nature, Hutton saw that the land is undergoing a ceaseless process of degradawith its manifold varieties of plant and animal life, will perish after tion, through the influence of the air, frost, rain, rivers and the sea, having existed for 132,000 years.
and that in course of time, if no countervailing agency should inter Buffon's conception of the operation of the geological agents did vene, the whole of the dry land will be washed away into the sea. not become broader or more accurate in the interval between the But he also perceived that this
universal erosion is not everywhere appearance of his two treatises. He still continued to believe in carried on at the same rate; that it is specially active along the the lowering of the ocean by subsidence into vast subterranean channels of torrents and rivers, and that, owing to this difference cavitics, with a consequent emergence of land. He still looked on these channels are gradually deepened and widened, until the volcanoes as due to the burning of "pyritous and combustible complicated valley-system of a country is carved out. He recognized stones," though he now called in the co-operation of electricity. that the detritus worn away írom the land must be spread out over He calculated that the first volcanoes could not arise until some the floor of the sea, so as to form there strata similar to those that 50,000 years after the beginning of the world, by which time a compose most of the dry land. As he could detect in the structure sufficient extent of dense vegetation had been buried in the earth of land convincing evidence that former sea floors had been elevated to supply them with fuel. He appears to have had but an imperfect to form the continents and islands of to-day, he could look forward acquaintance with the literature of his own time. At least there to future ages, when the same subterranean agency which had raised can be little doubt that had he availed himself of the labours of his up the present land would again be employed to uplift the bed of own countryman, Jean Etienne Guettard (1715-1786), of Giovanni the existing ocean, thus to renew the surface of our earth as a Arduino (1714-1795) in Italy, and of Johann Gottlob Lehmann habitable globe, and to start a fresh cycle of erosion and deposition. (d. 1767) and George Christian Füchsel (1722-1773) in Germany, he Though Hutton was not unaware that organic remains abound in would have been able to give to his epochs" a more definite succes many of the stratified rocks, he left them out of consideration in sion of events and a greater correspondence with the facts of nature. the elaboration of his theory. It was otherwise with Among the writers of the 18th century, who formed philosophical one of his French contemporaries, the illustrious J. B.
Lamarck conceptions of the system of processes by which the life of our earth Lamarck (1744-1829), who, after having attained great eminence as as a habitable globe is carried on, a foremost place must be assigned a botanist, turned to zoology when he was nearly fifty years of age. to James Hutton (1726-1797). Educated for the medical profession, and before long rose to even greater distinction in that department