of the earth was at this time known to the scientific schools of Alexandria, and the system of Eratosthenes was based upon its recognition, though he disregarded the great primal features of modern geographical science, the equator, the poles, and the tropics. The base line of his geography was a parallel drawn from W. to E. through all the places where it was supposed that the longest day was 143 hours. It stretched from Cape St. Vincent in Spain eastward through Rhodes, Asia Minor, Persia, and India, till it terminated at the city of Thine, which was supposed to be on the shores of the eastern ocean at the utmost extremity of the earth. The distance from one extremity of this line to the other, according to Eratosthenes, was about 70,000 stadia, or 9,000 miles. At right angles to this parallel Eratosthenes traced a meridian which passed through Rhodes and Alexandria southward through Syene and Meroë, till it reached what was supposed to be the uninhabitable region, the northern bounds of which were fixed at 12 degrees from the equator. Thule was regarded by Eratosthenes as the extreme northern end of the earth, and the distance from there to the habitable limit toward the equator was computed at 38,000 stadia, or nearly 5,000 miles. Beyond these limits of 9,000 miles in length and 5,000 miles in breadth it was commonly supposed that nothing existed but an impassable ocean, though Eratosthenes cautiously conjectures that there might exist in it continents and islands which could be reached by sailing westward. Hipparchus, a Bithynian who lived at Rhodes (160-145 B. C.), carried still further the system adopted by Eratosthenes, and subjected the whole science of geography to astronomical principles. He made numerous observations of latitude in addition to the few previously existing, and pointed out the mode in which longitudes might be ascertained by observing the eclipses of the sun and moon. But Hipparchus was greatly in advance of his age, and his dis coveries were neither appreciated nor applied to any practical use till long after his time. Somewhat more than a century after Hipparchus, Strabo, a Greek of Pontus and a great travel ler, wrote a geography which embodies all that was known of the science at the beginning of the Christian era. The countries immediately around the Mediterranean were known with tolerable accuracy; but the Atlantic shores of Europe were very erroneously comprehended, while of the northern and eastern portions only the vaguest ideas were entertained. Nothing whatever was positively known of Scandinavia, Russia, or of northern Germany. The extent of Europe to the E. and N. E. was greatly exaggerated, while that of Asia was proportionally underrated. Nothing was known of Siberia, Tartary, China, Japan, or the great Asiatic archipelago. The Ganges was thought to have throughout an easterly course, and to flow into the eastern ocean. The Caspian was supposed to be the limit of the earth to the N., and to be

connected with the eastern ocean by a sea occucupying the space now known to be covered by Siberia and Tartary. Of Africa only the northern part was known, S. of which was thought to be an uninhabited and uninhabitable torrid zone. The belief in the probability of circumnavigating Africa, which had existed in previous ages, was rejected by Strabo, though he held to the theory of an encircling ocean. A still more famous geographer than Strabo was Ptolemy, who lived at Alexandria about the middle of the 2d century after Christ. At this period the Roman empire had reached its greatest extent, and all its provinces had been surveyed and were well known. Large advances had been made in the knowledge of the countries outside of the empire. The notion of a circumambient ocean had been given up, and an indefinite expanse of terra incognita substituted as the supposed boundary of the world. Africa, however, was represented as stretching indefinitely S., and it was even carried round to join the E. of Asia, so that the Indian ocean was enclosed like the Mediterranean. In Europe, Spain and Gaul were for the first time correctly delineated, together with the southern part of Britain. The outline of Scotland and the relative position of Ireland are very incorrectly given. Thule is laid down as an island upward of 100 m. in length. From its position it is probable that some part of Norway was meant. Northern Germany and the southern line of the Baltic coast were tolerably well known, as was also some portion of Russia in the neighborhood of the Baltic and the southern part of Russia in Europe. In Asia, great regions had become known sufficiently to make it certain that they were inhabited by nomade tribes called Scythians, while from the far east some vague report of China and of the regions now known as Chin-India had reached the geographer. From the time of Ptolemy till the revival of letters in Europe little progress was made in geographical knowledge. In the 13th century missions were sent by the popes into remote parts of Asia. Father John de Plano Carpini, with some Franciscan monks, was sent in 1246 by Innocent IV. to Kayuck Khan, the Tartar emperor, and penetrated as far as Thibet. In 1253 Rubruquis, another Franciscan, was sent by Louis IX. of France in search of Prester John, and penetrated further into Asia than any European had ever before done. But the greatest discoveries in this quarter were made by the celebrated Marco Polo, a Venetian noble, who in 1265 set out with his father and uncle on a journey to the court of Kublai Khan, the Tartar conqueror of China. After travelling for more than 3 years they reached Yeh-king, near where Pe-king now stands. Marco Polo resided 17 years in the East, and on his return gave an account of his travels, which first made known to Europe the existence of Japan and of many of the East Indian islands and countries. In the 15th century the spirit of enterprise and of geographical exploration was strongly aroused in Europe. Portugal

took the lead, and made great and systematic efforts to explore the unknown countries on the W. coast of Africa. In the year 1412 Cape Non was doubled, and soon afterward the islands of Porto Santo and Madeira were discovered. In 1484 Benin and Congo were discovered, and the coast explored for 1,500 miles S. of the equator. Finally in 1486 the cape of Good Hope was reached, and 11 years later doubled by Vasco da Gama. But the greatest of all geographical discoveries was that of the new world by Christopher Columbus in 1492. From this time forward the progress of geographical exploration was exceedingly rapid. Within 30 years from the date of the first voyage of Columbus the whole E. coast of America from Greenland to Cape Horn had been explored, and Spanish keels were floating on the Pacific ocean. In 1520 Magellan passed the straits which bear his name, and his vessel, crossing the Pacific and Indian oceans, returned to Europe by way of the cape of Good Hope, having for the first time circumnavigated the globe. The W. coast of America, with the exception of that portion N. of the bay of San Francisco, was explored before the middle of the 16th century, while considerable progress was made by the Spaniards in acquiring a knowledge of the interior of South America. At the same time discovery in the East advanced with rapid strides. Within 20 years from the time of Gama's arrival in India, the coasts of E. Africa, Arabia, Persia, Hindostan, and Further India had been explored, and many of the islands of the great archipelago discovered. In the 16th and 17th centuries the progress of astronomical science led to a general revision of Ptolemy's tables of latitude and longitude, which had for ages been received with implicit confidence, but which more accurate observations now proved to be generally erroneous. In the 18th century many learned and laborious writers, among whom M. d'Anville may be particularly mentioned, applied themselves to the rectification of the whole system of ancient geography, and to the identification of ancient with modern countries, cities, rivers, mountains, and other features. The desire to discover a shorter route to India than those by Cape Horn and the cape of Good Hope led the English and the Dutch in the 16th century to make daring and persevering efforts to effect a N. E. and a N. W. passage. For a long time the opinion prevailed that the northern extremity of America terminated, like the south ern, in a point or cape, by sailing round which the mariner could enter the Pacific ocean and make his way to India. The expeditions of Sir Hugh Willoughby and Richard Chancellor in 1553, of Frobisher in 1576-'8, of Davis in 1585-'8, of Barentz in 1594-'6, in search of this northern route, greatly enlarged our knowledge of the arctic regions, and especially of the N. E. part of North America. So too in the succeeding century a similar result followed from the voyages of Henry Hudson, in 1607-'11, and of William Baffin in 1616. It was not till the

latter part of the 18th century, however, that the great breadth of the upper part of North America became fully known from the investigations of Capt. Cook in his voyages to the Pacific. The determination of the distance from Behring's straits to the E. coast of North America dispelled for a time all expectation of a N. W. passage. It was supposed that the continent stretched in one unbroken mass to the pole. The discoveries of Hearne in 1771 and of Mackenzie in 1789, by showing that an ocean bounded America on the north, dispelled these ideas, and in 1818 the attempt to effect the N. W. passage was revived by an expedition commanded by Capt. Ross. This was the beginning of a series of English and American expeditions to the arctic regions, which have within a few years greatly advanced our knowledge of that part of the world, though without attaining the object for which they were commenced. (See ARCTIO_DISCOVERY.) Early in the 17th century the Dutch, while seeking for a southern continent whose existence was supposed necessary to balance the northern continent, discovered Australia, which they called New Holland, and explored a considerable portion of its coasts. In 1642 Tasman discovered Van Diemen's Land, or Tasmania, as it is now called. Soon afterward he discovered New Zealand and several of the Polynesian groups. His explorations proved that New Holland was an island, and not a part of the southern continent. The famous Capt. Cook in his voyages, 1768-'79, made strenuous efforts without success to discover the southern continent. He however added largely to geographical knowledge by his survey of the Pacific ocean and its innumerable islands. An expedition sent out by the United States in 1838, under command of Lieut. Wilkes, succeeded in 1840 in discovering a continent within the antarctic circle, portions of which were also seen in the same year by the French and English navigators Dumont d'Urville and Sir James Ross. (See ANTARCTIO DISCOVERY.) Our acquaintance with the interior of Asia has been greatly advanced within the last two centuries by a multitude of travellers, prominent among whom have been the Jesuit missionaries, so that at the present day our general knowledge of the continent of Asia is tolerably complete. No great terra incognita remains, though fuller and more precise information about the vast regions known as Tartary is much to be desired. The travels of Humboldt, of Lewis and Clark, and of Fremont have perfected our acquaintance with the interior of the American continent. The interiors of Australia and of Africa are however still only partially known. Much has been done for the exploration of the former by Sturt, Eyre, and Leichhardt, while in Africa a host of travellers have struggled for a century past to penetrate the mystery which from the remotest period has enveloped that great division of the globe. Foremost among the African explorers we may name James Bruce, Mungo Park, Major Denham, Lieut. Clapperton, Richard Lander, Cap

tain Burton, Dr. Livingstone, and Dr. Barth. Great additions have been made to our knowledge of the countries on the upper Nile by expeditions recently sent by the pasha of Egypt, which have penetrated far beyond the region so long assigned on our maps to the mountains of the Moon. These expeditions and the researches of Barth, Burton, Livingstone, and the missionaries Rebmann and Krapf, have left in obscurity only a portion of that part of Africa which lies between lat. 10° N. and 10° S. The veil that still hangs over that will doubtless soon be dispelled, so that of the whole earth nothing will remain wholly unknown to the science and the curiosity of civilized man except the frozen regions round the poles. The remarkable progress of geographical discovery within the last half century has been thus summed up by Mr. Bayard Taylor: "Within that time all the principal features of the geography of our own vast interior regions have been accurately determined; the great fields of central Asia have been traversed in various directions from Bokhara and the Oxus to the Chinese wall; the half-known river systems of South America have been explored and surveyed; the icy continent around the southern pole has been discovered; the N. W. passage, the ignis fatuus of nearly two centuries, is at last found; the Dead sea is stripped of its fabulous terrors; the course of the Niger is no longer a myth, and the sublime secret of the Nile is almost wrested from his keeping. The mountains of the Moon, sought for through 2,000 years, have been beheld by a Caucasian eye; an English steamer has ascended the Chadda to the frontiers of the great kingdom of Bornou; Eyre, Leichhardt, and Sturt have penetrated the wil derness of Australia; the Russians have explored the frozen shores of northern Siberia, and descended from Irkutsk to the mouth of the Amoor; the antiquated walls of Chinese prejudice have been cracked, and are fast tumbling down; and the canvas screens which surrounded Japan have been cut by the sharp edge of American enterprise. Such are the principal features in the progress of modern discovery. What half century since the form of the earth and the boundaries of its land and water were known, can exhibit such a list of achievements?" -The literature of geography has within a few years undergone a marked change. Instead of the formal, regular descriptions of the earth and its inhabitants, which were once in vogue, gazetteers and geographical dictionaries are now popular. (See GAZETTEER.) The progress of geography has been much aided during this century by the efforts of zealous geographical societies, among which those of England and France are particularly distinguished. Their transactions, issued periodically, contain a vast and constantly increasing mass of information. Among the best works on geography are Précis de la géographie universelle, ou description de toutes les parties du monde sur un plan nouveau, d'après les grandes divisions du globe, by Malte

Brun (Paris, 1810-27), of which a translation into English was made by the late James G. Percival, 1827-32, under the title of "Universal Geography" (6 vols. 8vo., Philadelphia, 1827'32); "An Encyclopædia of Geography," by Hugh Murray (1 vol., London, 1835; 3 vols., Philadelphia, 1836; new edition, 1857); Karl Ritter's great work, Die Erdkunde im Verhält nisse zur Natur und Geschichte des Menschen, and many other works by the same author and by his followers, Von Rougemont, Von Roon, Berghaus, Volger, Merleker, Meinicke (Lehrbuch der Geographie, 1857), and Klöden (Handbuch der Erdkunde, 1858). Smith's "Dictionary of Greek and Roman Geography" (2 vols. 8vo., London, 1854-'7) contains a full and methodical compendium of all that remains of the geographical knowledge of the ancients.

GEOLOGY (Gr. yn, the earth, and λoyos, discourse), the science which treats of the structure of the earth and the methods by which its materials have been arranged. Its study embraces all matters that form the portion of the earth within the reach of man's observation; it brings them together into appropriate groups, and investigates the changes through which they have passed. It thus divides itself into 2 departments, descriptive geology and physical geology, the latter treating especially of the causes of production, or of geological dynamics. In this department a close connection and mutual dependence are perceived at the outset between this and the other physical sciences. Some of the laws which affect the distribution and condition of masses upon the surface of the earth are more perfectly comprehended in the grander scale of their action, as they influence the movements and condition of the heavenly bodies; others are to be explained only by ref erence to meteorological agencies, as the rains, frost, winds, &c.; others by the mechanical forces exerted by running water; and a large class depend for their exposition on the chemical operations that are everywhere going on, changing the conditions of matter, and even in the still depths of the sea and the apparently unchangeable strata deeply buried in the earth, producing grander results than those displayed by the noisy eruptions of the volcano. So closely are all departments of nature linked together, that even the habits of insignificant insects, as already explained under ČORAL, must be studied to account for the formation of geological structures of vast extent; and under ALLUVIUM it is shown that the infusoria, the minutest organic forms that we can recognize, make up by their shelly remains the substance of extensive deposits. The vegetable kingdom, too, has contributed an important share to the materials that compose the strata of the earth; and botany is thus enlisted to elucidate geological phenomena, while its own sphere is enlarged by the strange flora of past epochs faithfully preserved in geological herbaria. Many of the rocks are found filled with shells, and containing relics of various other animal forms; whence

conchology and zoology become aids to geological investigations as requisite as botany, and are themselves similarly advanced by the new field thus opened to them. Comparative anatomy also has been so extended by the demands of geology for an explanation of the true character of the bones and other animal remains preserved in the rocks, and differing strangely from all belonging to known living forms, that this may be regarded almost as a new science.The changes that have taken place in the inorganic and organic world introduce in their study considerations of time and progress, and the science is found to partake largely of the historical character. It abounds with records of past events, and the geologist, as Cuvier remarked, is an antiquary of a new order. Its historical element is regarded by Lyell as so prominent that he defines geology simply as "the science which investigates the successive changes that have taken place in the organic and inorganic kingdoms of nature."-In the present article little more will be attempted than to present a general sketch of the history and progress of geological science, a reference to some principal objects of its pursuits, and the systems of classifying the groups of rock generally adopted. The history of the science as developed in Europe is minutely traced in the familiar work of Lyell, "Principles of Geology," in which the whole subject may also be most advantageously studied; while for special details reference may be made to the names of the formations and of the minerals, metals, &c., in their alphabetical arrangement in this cyclopædia. (See also MINERALOGY, and PALEONTOLOGY.)—From the earliest times the structure of the earth has been an object of interest to man, not merely on account of the useful, materials he obtained from its rocky formations, but also for the curiosity awakened by the strange objects it presented to his notice. The south and west of Asia and much of the country bordering the Mediterranean were particularly favorable for directing attention to geological phenomena. Earthquakes were of frequent occurrence, changing the relative position of sea and land; volcanoes were seen in operation, adding layers of molten rock to those of sand and mud filled with the shells of the Mediterranean; the strata in the hills abounded in evidences of similar collections of vestiges of marine life far removed from access of the sea, and yet unchanged during the period of human observation and tradition; the Ganges and the Nile pouring forth their vast sedimentary accumulations were plainly building up the deltas at their mouths, and the broad valleys reaching far up their course were unmistakable productions of the same series of operations in remote periods of time. These phenomena could not escape the attention of the philosophers among the ancient Egyptians and Indian races; and their influence is perceived in the strange mixtures of correct observations and extravagant conceits which make up their cosmogonies or universal theories of the creation. In the first

chapter of the ordinances of Manu alternating periods of destruction and of renovation are distinctly recognized, extending in eternal succession throughout the whole assemblage of locomotive and immovable creatures, each period comprehending a duration of many thousand ages. The Greek schools of philosophy recognized these phenomena, which were clearly enunciated by Ovid in presenting the doctrines of Pythagoras. Remarkably free from extravagant statements, they were applied to prove a system of perpetual change slowly modifying the surface of the earth. Aristotle recognized the interchanges constantly taking place between land and sea by the action of running water and of earthquakes, and remarked how little man can perceive in the short span of his life of operations extending through the eternity of time. Strabo distinctly applied the rising up of lands, not merely of small tracts, but of continents also, by earthquake convulsions, to account for the perplexing phenomenon of beds of marine shells contained in the interior of hills far distant from the sea. Arabian philosophers of the 10th century are cited who entertained similar views of the changes going on and their causes; and in an Arabian manuscript of the 13th century, preserved in the royal library at Paris, the changes that may occur in successive periods of 500 years are happily presented in the beautiful narrative of the mythical traveller Kidhz.-The Italian philosophers in the early part of the 16th century were the first to engage in systematic investigations concerning the true nature of fossil shells. Their abundance in the strata of the sub-Apennine range could not fail to arrest attention and excite inquiries, now the more perplexing from the limited time allowed in popular belief to the past duration of the earth, and from the general persuasion that no great catastrophe except the Noachian deluge could have occurred to modify its surface. Various fanciful explanations were therefore adopted in the spirit of the scholastic disputations, and for 3 centuries argumentations were sustained with much spirit on the questions: first, whether fossil remains had ever belonged to living creatures; and secondly, admitting this, whether all the phenomena could not be explained by the deluge of Noah. Among those distinguished for the soundness of their views in the commencement of this controversy are Leonardo da Vinci, the celebrated painter, who died in 1519, and Fracastoro, whose attention was engaged by the multitude of curious petrifactions which were brought to light in 1517 in the mountains of Verona in quarrying materials for repairing the city. He exposed the absurdities of the theories which referred the petrifactions to a certain plastic force in nature that could fashion stones into organic forms, and showed the inadequacy of the traditional deluge to collect marine fossils that form solid strata of the earth. About this time collections of these curiosities were made for public museums and

make it conform to the received interpretation of the scriptural account of the creation and deluge. The Italian geologists Vallisneri in 1721, Moro in 1740, and Generelli in 1749, advanced the most philosophical views yet presented respecting the fossiliferous strata, and sustained them by original observations made by the first two throughout Italy and among the Alps. Moro endeavored to make the production of strata correspond in time to the account of the creation of the world in 6 days, and hence was compelled to refer them to volcanic ejections, which by floods, he imagined, were distributed over the surface of the earth and piled up in strata with marvellous celerity. Buffon advanced views respecting the formation and modification of mountains and valleys by the action of water in his "Natural History" (1749), a portion of which, contained in 14 propositions, he was required by the faculty of theology in Paris to renounce. This he did in his next work, accompanying the formal abandonment of what he had written contrary to the narration of Moses with a declaration of belief of all contained in the Scripture about the creation, both as to order of time and matter of fact.-Geology did not begin to assume the rank of an important science until its application to the practical purposes of mining was first pointed out in the last quarter of the 18th century by Werner, professor of mineralogy in the school of mines at Freiberg in Saxony. This distinguished man by his wonderful genius attracted pupils from distant countries, and sent them forth enthusiastic geologists and advocates of the views he had conceived from his imperfect observation of the geology of a small portion of Germany. He taught the systematic order of arrangement of the strata, adopting nearly the same divisions that had been proposed 50 years previously by Lehmann, a German miner. He explained their production as the result of precipitation from a common menstruum or "chaotic fluid," which he supposed had once covered the whole surface of the earth. As expounded by Jameson in 1808, the first precipitates from this ocean were chemical, and produced the crystalline rocks which lie at the base of all the others, and which he designated as the primitive class. They included the granitic rocks and those since called metamorphic, as gneiss, mica slate, clay slate, serpentine, &c. The 2d class comprised the rocks he calls transition, certain limestones, flinty slate, gypsum, graywacke, and trap, most of which are probably now included in the silurian formation. They were supposed to have been formed during the transition of the earth from its chaotic to its habitable state, and to have been partly chemical and partly mechanical in their origin, the latter worn down by the waves and currents. The 3d class contained the rocks denominated Floetz, because as observed in Germany they were disposed in horizontal or flat strata. In this was the coal formation, rock salt, chalk formation, old red

private cabinets; they were deposited in the museum of the Vatican at Rome, and that of Canceolarius at Verona became famous for them. Descriptive catalogues of these collections were published; and as early as 1565 appeared one of the collection of John Keutman in Gessner's work De Rerum Fossilium, Lapidum, et Gemmarum Figuris. In 1580 Palissy was the first who dared assert in Paris that fossil remains of testacea and fishes had once belonged to marine animals. The truth, however, made but slow progress in the face of the established prejudices of the times. In 1669 Steno, professor of anatomy at Padua, published his work De Solido intra Solidum naturaliter Contento, in which he proved the identity of the fossil teeth found in Tuscany with those of living sharks, and the close similarity of the fossil testacea to living species; he traced their progressive change from unaltered shells to solid petrifactions, and recognized the distinction between formations deposited by salt and by fresh water, and that some were of an earlier period than the introduction of plants and animals upon the earth. But neither he nor Scilla, the Sicilian painter, who in his Latin treatise on the fossils of Calabria, published in 1670, and illustrated by good engravings, ably maintained the organic nature of fossil shells, ventured to refer their occurrence in the strata to any other cause than the Mosaic deluge. Leibnitz, the great mathematician, in his Protogæa, published in 1680, first proposed the theory of the earth having originally been a burning luminous mass, which since its creation has been cooling down, and as it cooled received the condensed vapors which now compose its crust. In one stage of its formation he believed it was covered with a universal ocean. From these materials Leibnitz traced two classes of primitive formations, the one by refrigeration from igneous fusion, the other by concretion from aqueous solution. The first recognition of the arrangement of the earthy materials in strata, continuous over large areas, and resembling each other in different countries, appears to have been by Dr. Lister, who sent to the royal society in 1683 a proposal for maps of soils or minerals. He also believed that species had in past epochs become extinct. Dr. Robert Hooke prepared near the close of the 17th century a 66 Discourse on Earthquakes," which contains the most philosophical views of the time respecting the nature of fossils and the effects of earthquakes in raising up the bed of the sea. William Woodward was a distinguished observer of the geological formations of Great Britain, and perceived that the lines of outcrop of the strata were parallel with the ranges of the mountains. He formed about the year 1695 a collection of specimens which he systematically arranged and bequeathed to the university of Cambridge. For this he purchased the original specimens and drawings of fossil shells, teeth, and corals of Scilla, the Sicilian painter noticed above. But his geological system was cramped by the attempt to