158 MINERAL AND ZOOLOGICAL CHARACTERS. 



mountain ranges, the mineral characters of the upper secondary 

 limestones also frequently undergo a considerable change, and be- 

 come indurated and crystalline, like transition liniestones. 



It has been stated in the preceding chapters, that the coal strata, 

 which are interposed between the transition rocks and the secondary 

 strata, contain, almost exclusively, the organic remains of terrestrial 

 and lacustrine or marsh plants, while the fossils in the lower or transi- 

 tion class, belong, almost exclusively, to marine animals. Another 

 great change appears to have taken place in the condition of our 

 planet, after the deposition of the coal strata, for the upper seconda- 

 ry strata contain, principally, the remains of marine animals. It is 

 in the strata belonging to this class, that the bones and entire skele- 

 tons of enormous reptiles are first discovered. It is, however, truly 

 remarkable, that throughout the whole series of the upper secondary 

 strata, no bones of mammiferous land quadrupeds have yet been 

 found ; the strata at Stonesfield alone present a solitary exception. 



In England, the order of succession of the upper secondary rocks 

 may be more distinctly ascertained, than in any other country that 

 has yet been examined. I shall therefore describe them as they oc- 

 cur in our own country, with references to foreign localities, where 

 the same beds or formations are well identified with the English 

 strata. Geologists on the Continent, and particularly in France, had, 

 till very recently, no accurate knowledge respecting several of these 

 formations ; and their classifications of them were vague and contra- 

 dictory. More attention, however, has, very lately, been directed 

 to this part of the geology of France ; and the clear accounts which 

 have been published, by M. Elie de Beaumont in particular, of some 

 of these formations, remove much of the obscurity which prevailed 

 respecting them, and prove, in a satisfactory manner, the great simi- 

 larity which may be observed, in the secondary formations of Eng- 

 land and France. 



In the following tabular arrangement of the secondary formations, 

 above the transition and coal formations, I have not thought it expe- 

 dient to introduce all the minor subordinate beds in each formation : 

 those which possess any geological importance will be subsequently 

 noticed. It may be frequently observed, that particular beds which 

 occur in one part of a formation, and are considerably developed, 

 cannot be traced even into an adjacent district, or they vary so much 

 in thickness and mineral characters, as scarcely to be recognized. 

 If we take an extensive formation, like the oolites, as an example, 

 it is not possible to assign any one part of the range, as affording a 

 correct type of all the series in distant or even in neighf)oring parts 

 of the range, though we may trace a general resemblance in all the 

 principal beds ; and this I hold to be amply sufiicient for every valu- 

 able purpose in geology.* 



* Those who know into how many mistakes even eminent geologists have fall- 

 en, respecting the formations in their own immediate vicinity, by attempting to 



