182 PRINCIPLES OF CLASSIFICATION [Ch. XIIL 



practically it will lead to no misapprehension as to the chronological 

 sequence of formations. 



The origin of the terms Primary and Secondary was explained in the 

 eighth chapter, p. 92. 



The Tertiary strata were * so called because they were all posterior 

 in date to the Secondary series, of which last the Chalk or Cretaceous, 

 No. 9, fig. 140, constitutes the newest group. The whole of them 

 were at first confounded, as before stated, p. 87, with the superficial 

 alluviums of Europe ; and it was long before their real extent and 

 thickness, and the various ages to which they belong, were fully re- 

 cognized. They were observed to occur in patches, some of fresh- 

 water, others of marine origin, their geographical area being usually 

 small as compared to the secondary formations, and their position 

 often suggesting the idea of their having been deposited in differ- 

 ent bays, lakes, estuaries, or inland seas, after a large portion of the 

 space now occupied by Europe had already been converted into dry 

 land. 



The first deposits of this class, of which the characters were accurately 

 determined, were those occurring in the neighborhood of Paris, described 

 in 1810 by MM. Cuvier and Brongniart. They were ascertained to con- 

 sist of successive sets of strata, some of marine, others of freshwater 

 origin, lying one upon the other. The fossil shells and corals were per- 

 ceived to be almost all of unknown species, and to have in general a 

 near affinity to those now inhabiting warmer seas. The bones and skel- 

 etons of land animals, some of them of large size, and belonging to more 

 than forty distinct species, were examined by Cuvier, and declared by him 

 not to agree specifically, nor even for the most part generically, with any 

 hitherto observed in the living creation. 



Strata were soon afterwards brought to light in the vicinity of London, 

 and in Hampshire, which although dissimilar in mineral composition, 

 were justly inferred by Mr. T. Webster to be of the same age as those of 

 Paris, because the greater number of the fossil shells were specifically 

 identical. For the same reason rocks found on the Gironde, in the South 

 of France, and at certain points in the North of Italy, were suspected to 

 be of contemporaneous origin. 



A variety of deposits were afterwards found in other parts of Europe, 

 all reposing immediately on rocks as old or older than the chalk, 

 and which exhibited certain general characters of resemblance in their 

 organic remains to those previously observed near Paris and London. 

 An attempt was therefore made at first to refer the whole to one pe- 

 riod ; and when at length this seemed impracticable, it was contended 

 that as in the Parisian series there were many subordinate formations 

 of considerable thickness which must have accumulated one after the 

 other, during a great lapse of time, so the various patches of tertiary 

 strata scattered over Europe might correspond in age, some of them 

 to the older, and others to the newer, subdivisions of the Parisian 

 series. 



