sandstone, numerous floetz limestones and floetz trap. They were supposed to have been formed while animals and vegetables existed in numbers, and to have been partly chemical and partly mechanical in their origin. They were not regarded as corresponding to the "secondary" of the French geologists, as this division comprehended some of Werner's transition class; still the division secondary is sometimes found among Werner's, as it was used by Lehmann. The 4th class contained the alluvial rocks, those produced on the land, as peat, sand and gravel, loam, bog iron ore, cale tuff, &c., being understood to comprise all above the chalk excepting the volcanic; the tertiary are thus entirely overlooked. The 5th class comprised the volcanic rocks, the pseudo-volcanic, and the true volcanic-the former being real or imaginary products of the combustion of coal and sulphurous matters, the latter of real volcanoes. These formations were supposed to be systematically arranged; the later formed either entirely covering the older, or, when these form a central mountain mass, encircling this, so that the "outgoings" of the strata (meaning their upper edges or lines of outcrop) form circles; those of the later formed groups being successively larger. The basin and troughshaped deposits were also recognized, in which the outgoings of the newer strata became successively smaller. The strata, it was understood, were subject to local disturbances from portions sinking into subterranean cavities, and members might be wanting in some localities, but whenever present must be found in their proper position in relation to the rest. Basalt, which in Saxony and Hesse was seen capping the hills of stratified rocks, he inferred must be of the same series of precipitated formations, although many other geologists of Werner's time had fully established the analogy between this rock and modern lavas. The observations of Desmarest, especially in the district of extinct volcanoes in Auvergne, made in 1768, are referred to by Lyell as most clearly tracing the origin of the basalts to the craters of the volcanoes. A new controversy now arose, which for many years was waged with animosity and bitterness unprecedented in all other disputes of this class. Geologists throughout Europe were divided into the two classes of Neptunists, who advocated the production of the rocks by aqueous deposition alone, and Vulcanists, who attributed the origin of many of them to the action of fire. Hutton of Edinburgh was the acknowledged leader of the latter party. He had studied geology for himself in different parts of Scotland and England, and formed his own conclusions, which he ably sustained. He was the first to announce that geology had no concern with questions as to the origin of things, but that the true field of her investigations was limited to the observation of phenomena and the application of natural agencies to explain former changes. His friend Sir James Hall showed by actual experiment that the prismatic

structure of basalt might result in cooling from a state of igneous fusion; and Hutton himself rejoiced to find in the Grampian hills the granite branching out in veins, which extended from the main body through the contiguous micaceous slates and limestone, thus indicating its having been in a fused state, and this subsequent to the production of Werner's later formed rocks. This discovery soon led to questioning the existence of any primitive class of rocks, the origin of which lay beyond the reach of the present order of things; and the announcement made by Hutton: "In the economy of the world I can find no traces of a beginning, no prospect of an end," may well have startled men of science and shocked the religious public in the sensitive condition to which it had been brought by the infidel doctrines promulgated in the latter part of the last century, especially by men of letters of France. The Vulcanists came to be classed with the enemies of Scripture, the true object of investigation was lost sight of, and the controversy was continued with such animosity that the party names at last became terms of reproach, and many geologists avoided being involved in it. Workers in the field, however, were collecting new and valuable data that were to give to the science a more exact character. William Smith, a civil engineer, prepared in 1793 a tabular view of the strata near Bath, tracing out their continuity over extensive areas, and recognizing them by the fossils they contained. This method of identification and of arranging strata in their true positions he taught himself, and was the first to promulgate in England. With extraordinary perseverance he continued to prosecute his work alone, travelling on foot over all England, freely communicating his observations, and in 1815 he completed a geological map of the whole country. In France the importance of fossils as characteristic of formations was also beginning to be appreciated. De Lamarck and Defrance earnestly engaged in the study of fossil shells, and the former in 1802 reconstructed the system of conchology to introduce into it the new species collected by the latter in the strata underlying the city of Paris and quarried for the construction of its buildings. Six years previous to this Cuvier had established the different specific character of fossil and living elephants, which opened to him, as he stated, views entirely new respecting the theory of the earth, and determined him to devote himself to the researches which occupied the remainder of his life. In 1807 the geological society of London was established, with the professed object of encouraging the collection of data, multiplying and recording observations, with no reference to any "theories of the earth." Its active members completed the classification and description of the secondary formations of Great Britain, so well commenced by William Smith; while at the same time the tertiary formations were thoroughly investigated by Cuvier, Brongniart, and others in Paris. Thus

each country contributed to the advancement of geological science in the department connected with its most prominent formations-Germany in that of the lower stratified and metamorphic rocks, and especially in the mineralogical structure of these, while in Scotland the character of the granitic rocks had been more particularly elucidated, in England that of the secondary strata and their order of arrangement, and in France the tertiary. The great principles gradually developed by these observations were: that the materials of the stratified rocks were sedimentary deposits that had slowly accumulated in the beds of ancient seas and lakes; that each stratum represented a certain period of time during which its materials were gathered, and that this period was characterized by its peculiar group of organized beings, the vestiges of which were buried and remained with it as records of the condition of this portion of the earth during this time. The piles of strata of various kinds indicated changes in the character of the deposits introduced, sandstones derived from sand alternating with shales derived from muddy and clayey deposits, and with calcareous strata, whose origin may have been in marl beds or coralline structures. The long succession of these strata, in connection with the evidences of their slow accumulation, observed in the undisturbed condition of the fossil remains they contained, bore witness to long periods of time occupied in the production of a single group of strata constituting but a minor division of one of the formations. The lapse of long periods of time was also indicated by the fossils becoming constantly more and more unlike existing species as found in beds of older date. The same localities, too, presented in their successive beds some that were filled with marine vestiges alone, corallines and sea shells clustered together as found in tropical oceans, and in layers of such thickness that ages must have passed while they were quietly accumulating; and above or below these were found other strata indicating that the surface was at another period covered with fresh water, the organic vestiges they contained being only of the character of those belonging to ponds and rivers; and yet again these localities became dry land, and were covered with the forests of tropical climes, and peopled with numerous strange species of animals, whose nearest living analogues are met with only in hot countries. Such changes as these also plainly marked slowly progressing_revolutions, the period of which no one could compute by years. It was apparent that the sediments had collected as beds of sand and clay now collect in seas and lakes, and especially about the mouths of large rivers; but it was only in such as were evidently the product of the streams of the present day that the organic vestiges were recognized as belonging entirely to familiar species. In these alone were discovered any relics of man or any indications of his existence; and here they were not wanting, for fragments torn off

by the anchor from the newly formed sandstone floor of the sea brought up the works of his hands already entombed as fossils; and in the calcareous strata in process of formation and filled with recent species of shells has been found his skeleton. But with the first step back, even to the strata that form the soil of living peat beds, the bones of extinct gigantic mammalia introduce us to strange groups of animals, and no positive evidence of a satisfactory nature is afforded, either in the strata or in tradition, that man was their contemporary. Thus in the closest connection, geologically speaking, are we presented with the most striking examples of other great principles developed by geological research, viz., the extinction of old and the introduction of new species.-In consequence of the system of observation and close investigation now established, geology lost its highly speculative character, and rapid progress continued to be made in acquiring correct information of the arrangement of the strata of different countries. While the defects of Werner's classification were exposed, the general plan of it was seen to be founded in nature, and attention was directed to collecting everywhere the materials for filling out the vertical column of the rocks, as well as mapping them throughout their horizontal range. In every country some formations could be recognized, from which as a base a local classification might proceed to contiguous groups, and thus at last the whole be included in one system of classification. So the work of descriptive geology has ever since been going on, new discoveries continually adding to its completeness; and yet, as in all other investigations into the works of an infinite Author, with no promise of approaching the object in view, viz., the compilation of a perfect system, which in this case should present a full chart of the rocks from the lowest or oldest to the uppermost or most recent. Strata lying in juxtaposition in one region, when identified in another, are found to be separated by the interpolation of a new series; and again, in tracing out over broad areas a group of sedimentary strata, they are found gradually to assume new features, and even to undergo an entire change of chemical composition. So it would be if the vast submarine surface now receiving the sediments deposited by the Gulf stream were uplifted to form a new continent; the geologists of a future period, exploring its strata among the forests and beneath the soil of its north-eastern hills, would find them composed of the finest materials, such as may have been deposited from chemical solution, and differing materially from the coarse sediment distributed further to the south-west. The fossil remains too would be different, though all belonging to the same epoch of production, and included in the same geological group. Were the beds of the great northern lakes at the same time also exposed to observation, their sediment and vestiges would be found essentially different from those of the strata of marine

origin; and yet certain characteristics would unmistakably refer the production of them all to the same period in the world's history-a period subsequent to the introduction of man. From this explanation it follows that all stratified formations must be of limited area and thinning away at their edges, presenting the shape of lenticular sheets lapping upon each other.-In 1819 the geological society published a map of England greatly improved upon that of Smith by the labors of Mr. Greenough and his friends. About the same time Leopold von Buch prepared a similar map of a large part of Germany. A geological survey of France was ordered in 1822 by the French government, by which a complete geological map of France was finally constructed in 1841. M. Bronchant de Villiers, professor in the school of mines, was appointed to take charge of the work, and with him were associated Elie de Beaumont and Dufrénoy. The attention of these geologists was first given to an examination of the strata above the coal formation in England, where they had been most carefully studied, and particularly described by Cony beare and Phillips in their treatise on the "Geology of England and Wales" (1821). The secondary strata of Germany also were familiar to geologists; and both countries consequently furnished important points of reference for the arrangement of the groups of France. The chalk formation of Paris, the upper member of the secondary, served as the starting point, and proceeding from this they examined in detail the lower strata as they appeared successively emerging from beneath it, and identified them as they could with the corresponding groups of other countries. Such is the method ever since pursued, by which our knowledge of the strata which make up the outer crust of the earth has been systematically extended. The importance of the organic remains found in the rocks has been more and more appreciated, and the shells which constitute the chief portion of these have been most thoroughly studied; for while the different formations or groups of strata may contain numerous similar beds of limestone, sandstone, slates, and shales, not to be distinguished by their mineral characters, and which frequently cannot be traced to their meeting with other known formations by which their place or relative positions may be determined, the fossils show no such indiscriminate distribution; but each era was characterized by its peculiar group of animated beings, and if their arrangement is understood it follows that the position of any stratum in which the fossils are recognized must also be determined. A single species may in some cases be peculiar to one member of a geological formation, and serve wherever the fossil is found to identify the rock; but usually in different countries their identification by fossils is dependent upon characteristic genera and the order of succession of their principal groups. This branch of the subject will be more particularly treated in the article PALEONTOLOGY.—

Before proceeding to a consideration of the classifications adopted by modern geologists, a rapid sketch will be presented of the progress of the science in the United States. In the latter part of the last and early part of the present century papers upon geological subjects occasionally appeared in the volumes of the philosophical society of Philadelphia, the "Transactions of the Boston Academy," and in other scientific journals. The character of these papers is almost exclusively descriptive. There is, however, a theory of the earth proposed by Franklin in the "Philosophical Transactions" of 1793. The 6th volume of the same journal presented the paper of Mr. William Maclure, read Jan. 20, 1809, entitled "Observations on the Geology of the United States, explanatory of a Geological Map." The author of this paper had undertaken a more arduous and gigantic work even than that which was occupying William Smith of England; it was no less than a geological survey of the United States alone and at his own expense-a work which entitled him to the appellation he has received of the father of American geology. In this pursuit he crossed the Alleghanies no fewer than 50 times, visited almost every state and territory in the Union, and for years continued his labors mostly among those who could have no appreciation of his objects. He had visited nearly all the mining districts of Europe, and was hence well qualified, for one of that period, to recognize the corresponding formations of the two continents. He traced out the great groups of strata then designated, as the transition, secondary, and alluvial, in their range from the St. Lawrence to the gulf of Mexico. The tertiary, however, he did not recognize, owing to the absence of the chalk formation, the upper member of the secondary, which in Europe, being largely developed and most conspicuous, marks the strata of more recent origin lying above it as tertiary. He continued his explorations after this report, and in May, 1817, presented another to the society, accompanied by a colored map and sections. His observations were also extended in 1816 and 1817 to the Antilles, and a paper upon the geology of these islands was published in the 1st volume of the "Journal of the Academy of Natural Sciences." Prof. Silliman of New Haven, educated to the profession of the law, was induced by President Dwight of Yale college to qualify himself for the departments of natural science, particularly chemistry; and with this view he spent some time previous to 1806 in England and Scotland. In Edinburgh he became familiar with the discussions of the Wernerians and Huttonians in that transition period, as he styles it, between the epoch of geological hypotheses and dreams, which had passed by, and the era of strict philosophical induction, in which the geologists of the present day are trained. The interest excited by this controversy could not fail to direct his tastes toward the new science, and he returned to become its zealous promoter, for half a century

or more aiding to elucidate the geology of his country, inspiring the enthusiasm of others, and furnishing in the "American Journal of Science" an organ for the diffusion of scientific knowledge. At that period (1804–5), he states, geology was less known in the United States than mineralogy. Most of the rocks were without a name, except so far as they were quarried for economical purposes, and classification of the strata was quite unknown. Dr. Archibald Bruce of New York commenced in 1810 the publication of a journal devoted principally to mineralogy and geology, the earliest purely scientific journal, as Prof. Silliman remarks, supported by original American communications. It was well received at home and abroad, but appeared only at wide intervals, and did not reach beyond the 4th number. The mineralogical collections at the principal colleges, and others belonging to scientific men mostly in New York, promoted inquiry and observation concerning the geological relations of the minerals and their distribution. The admirable treatise on mineralogy by Prof. Parker Cleave land, published in 1816, fostered while it gratified this spirit of inquiry. In 1818 the brothers Prof. J. F. Dana and Dr. Samuel L. Dana published a detailed report on the mineralogy and geology of the vicinity of Boston. In the same year the "American Journal of Science" was first published, which has continued ever since to be the chief periodical American recorder of the progress of the sciences. The next year the American geological society held their first meeting at New Haven, where they continued to meet annually for several years afterward. The importance of geological explorations, with the view of thereby ascertaining the agricultural and mineral capacities of large districts, was beginning to be appreciated by communities and public bodies. In 1820 a geological survey of the county of Albany, N. Y., was made under the direction of the agricultural society of the county by Prof. Amos Eaton and Dr. T. R. Beck. Two years afterward Rensselaer and Saratoga counties were also thus explored. Prof. Eaton was also engaged by Gen. Stephen Van Rensselaer to make at his expense a geological survey of the country adjacent to the Erie canal. The result of this was published in 1824 in a report of 160 pp. 8vo., with a profile section of the rock formations from the Atlantic ocean through Massachusetts and New York to Lake Erie, the Rev. Edward Hitchcock furnishing many of the details through Massachusetts. The first geological survey made by state authority was that of North Carolina in 1824 and 1825. The progress of these public undertakings is presented in the table upon the following page. The names are of the principal geologists, and most of the assistant geologists who reported under their own names. Beside these public surveys are others of importance made in connection with the government explorations between the Mississippi and the Pacific. Those of Schoolcraft, Nicollet, and Fre

mont are particularly worthy of reference. Nicollet, an accomplished astronomer from Savoy, devoted 5 years, from about 1833, to explorations made at his own expense in the western territories; and froin 1839 to the time of his death in 1843 he was in the service of the U. S. government preparing a map of these territories, which was published. Explorations have been recently made in connection with the survey of the Pacific railroad across the Rocky mountains, and in California by Jules Marcou, W. P. Blake, Dr. Antisell, and Dr. Newberry. American geology has also been greatly elucidated by the labors of private explorers, especially by Lyell in his two visits to the United States. Agassiz's contributions to its natural history are highly important for their geological bearings, likewise the earlier investigations in comparative anatomy of Dr. R. Harlan and of Dr. S. G. Morton, and those more recently made by Dr. Jeffries Wyman. Mr. Isaac Lea and Mr. William C. Redfield have made valuable contributions to the science from original investigations. For the grouping and identification of the members of the paleozoic formations over their wide range from the seaboard to the Rocky mountains, American geology is largely indebted to the labors of Prof. James Hall of Albany, who has acquired the most exact knowledge of their fossils, and materially advanced the science of palæontology. Our knowledge of the growth of coralline structures and their relation to the production of the calcareous formations of remote periods, as well as of other kindred geological subjects, has been greatly extended by the elaborate treatises of Prof. James D. Dana embodying the results of his observations made on the U. S. exploring expedition of Com. Wilkes from 1838 to 1842. The British provinces of North America have been explored by private enterprise and public patronage. A notice of the mineralogy and geology of Nova Scotia, with illustrations and a geological map, by Dr. C. T. Jackson and Francis Alger, Esq., of Boston, was published in the "American Journal of Science," 1828-'9; and in 1831 the same memoir, extended by further observations collected in a second visit to Nova Scotia, appeared in the "Transactions of the American Academy" at Boston. Lyell also has described interesting features exhibited in the coal measures of this peninsula. Extensive surveys have been made in Nova Scotia by Prof. Dawson, now of the McGill college, Montreal, and his work entitled "Acadian Geology" appeared in 1857. New Brunswick authorized a survey, the report of which was published by A. Gesner in 1839. Canada also passed a similar act in Feb. 1845, and Sir W. E. Logan has been actively engaged in carrying out this great work; his reports, accom panied by those of his assistants, T. Sterry Hunt, A. Murray, and others, having annually appeared since 1847. Newfoundland has been surveyed, under the government of the island, by Mr Jukes, who has since had charge of the geological survey of Ireland.

-From the time of Werner's system of the rocks, the classification of the formations has been subject to continual modifications; and many conventional or partial terms of distinction have been adopted, some of which still continue in common use, though not always strictly definitive. Thus, the rocks are frequently spoken of as either stratified or unstratified, the former being understood to comprise all those formations plainly due to sedimentary deposition, and the latter the granites and crystalline rocks, which present no distinct lines of stratification, but on the contrary forms and structure that imply the operation of other agents than those which produced the other class of rocks. The distinction is an excellent one, inasmuch as the names are simply descriptive and entirely free from any implication of relative age or position or mode of origin; but it is imperfect, as the crystalline rocks sometimes appear to be

stratified, and the lowest stratified formations lose their distinctive features as they assume in the class sometimes called metamorphic the forms and crystalline structure of the unstratified rocks. The term primary, much in use for the granitic rocks, is objectionable, as it implies priority of time in their production; and these rocks, as is abundantly proved, have in many instances assumed the position and structure in which they are found long after the deposition of some of the sedimentary rocks that repose upon the flanks of their mountain masses. Those of Mont Blanc and of part of the central axis of the Alps even invade strata of the tertiary epoch. (See ALPS.) The name igneous is also an objectionable designation, as it assumes a questionable theoretical origin, at least for many of the rocks that have been thus classed; and moreover, it must either admit the products of modern volcanoes into the same