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established prejudices. 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, illustrated by good engravings (1670), 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 (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 of London in 1683 a proposal for maps of soils or minerals. He also believed that species had in past ages become extinct. Dr. Robert Hooke near the close of the 17th century prepared a “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. About 1695 he formed 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. But his geological system was cramped by the attempt to 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 six 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 fourteen 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 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 fifty 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 called crystalline schists, such as gneiss, mica slate, clay slate, serpentine, &c. The second class comprised the rocks he calls transition, certain limestones, flinty slate, gypsum, graywacke, and trap, most of which are probably now included in the palæozoic formations. 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, and due to the action of the waves and currents. The third class contained the rocks denominated Flötz, because as observed in Germany they were disposed in horizontal or flat strata. In this were the coal formation, various sandstones, the chalk, rock salt, gypsums, various limestones, and certain traps. 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. The fourth class contained the alluvial rocks, those produced on the land, as peat, sand and gravel, loam, bog iron ore, calc tuff, &c., being understood to comprise all above the chalk excepting the volcanic. The fifth class comprised the volcanic rocks, the pseudo-volcanic, and the true volcanic; the former being the supposed products of the combustion