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Show 16 TERTIARY STRATA OF TilE PARIS BASIN. [Ch. II. points in the history of the discovery and classification of the tet"tiary strata. . . . P an·s B asm· . 'l'he first series of deposits belonging to tlus c1 a ss, o f wh 1. c h the characters were accurately d. etermined, w. ere those which occur in the neighbourhood of Pans, first de~cr1bed by MM. Cuvier and Brongniart*. They ~ere .ascertamed to fill a depression in the chalk (as the beds d, m diagram No. ~, rest upon c), and to be composed of different materials, some-· . No.2. a, Primary rocks. b, Older secondary formations, c, Chalk, d, Tertiary formation. times including the remains of marine animals, and sometimes of freshwater. By the aid of these fossils, several distinct alternations of marine and freshwater formations were clearly shown to lie superimposed upon each other, and various speculations were hazarded respecting the manner in which the sea had successively abandoned and regained possession of tracts which had been occupied in the intervals by the waters of rivers or lakes. In one of the subordinate members of this Parisian series, a great number of scattered bones and skeletons of land animals were found entombed, the species being perfectly dissimilar from any known to exist, as indeed were those of almost all the animals and plants of which any portions were discovered in the associated deposits. We shall defer, to another part of this work, a more detailed account of this interesting formation, and shall merely observe in this place, that the investigation of the fossil contents of these beds forms an era in the progress of the science. The * Environs de Paris, 1811. Ch , II.] TERTIARY STRATA OF SUCCESSIVE PERIODS, 17 French naturalists brought to bear upon their geological researches so much skill and proficiency in comparative anatomy and conchology, as to place in a strong light the importance of the study of organic remains, and the comparatively subordinate interest attached to the mere investigation of the structure and mineral ingt·edients of rocks. A variety of tertiary formations were soon afterwards found in other parts of Europe, as in the south-east of England, in Italy, Austria, and different parts of France, especially in the basins of the Loire and Gironde, all strongly contrasted to the secondary rocks. As in the latter class many different divisions had been observed to preserve the same mineral characters and organic remains over wide areas, it was natural that an attempt should first be made to trace the different subdivisions of the Parisian tertiary strata throughout Europe, for some of these were not inferior in thickness to several of the secondary formations that had a wide range. But in this case the analogy, however probable, was not found to hold good, and the et·ror, though almost unavoidable, retarded seriously the progress of geology. For as often as a new tertiary group was discovered, as that of Italy, for example, an attempt was invariably made, in the £rst instance, to discover in what characters it agreed with some one or more subordinate members of the Parisian type. Every fancied point of correspondence was magnified into undue importance, and such trifling circumstances, as the colour of a bed of sand or clay, were dwelt upon ac; proofs of identification, while the difference in the mineral charactet· and organic contents of the group from the whole Parisian series was slurred over and thrown into the shade. By the influence of this illusion, the succession and chronological relations of different tertiary groups were kept out of sight. The difficulty of clearly discerning these, arose from the frequent isolation of the position of the tertiary formations before described, since, a proportion as the areas occupied by them are limited, it is rare to discover a place where one Vor .. III. C |