THE PRE-ADAMITE EARTH. 



318. THE close of the Triassic age is identified with the convul- 

 sion to which M. Elie de Beaumont ascribes the elevation of the 

 Thuringerwald system of mountains, including the Bcehmerwald- 

 Gebirge, and the Morven ranges, the prevailing direction of which 

 is W. 40 N. and E. 40 S. M. D'Orbigny assigns to the same date 

 and cause the increased elevation of all the eastern part of the 

 Andes, included between* the 5 and 20 lat. S., and having the 

 direction W. 50 N. and E. 50 S. By combining with these dis- 

 locations the numerous discordances of stratification which are 

 observed, we shall find causes abundantly adequate to the expla- 

 nation of the total and sudden disappearance of the flora and 

 fauna of the Triassic age, to give place to the new creations of the 

 succeeding one. 



The Jurassic Age. 



319. Upon the Triassic formation the Jurassic has been depo- 

 sited, and is therefore the result of the next geological age. Many- 

 divisions of the strata composing this great formation have been 

 proposed, some based upon the mineralogical characters of the 

 strata, derived, however, in general, from observations more or 

 less local, and others from an imperfect generalisation of prevailing 

 fossils. We shall here adopt the analysis of this formation pro- 

 posed by M. D'Orbigny. " After many years of laborious obser- 

 vation," says that eminent palaeontologist, "during which we have 

 only advanced from confirmation to confirmation, without encoun- 

 tering any inconsistent facts, we have arrived at the conclusion 

 that the Jurassic formation consists of ten stages, or superposed 

 zones, limited and defined by their several fauna as distinctly as 

 by their stratigraphical characters. In tracing them one after the 

 other around various geological basins, we have ascertained that 

 they are nowhere confounded, and that they represent clearly ten 

 distinct epochs, one succeeding another in a constant and regular 

 order. We have ascertained that the same succession takes place 

 in the same order at all parts of the earth which have been sub- 

 mitted to exact observation, and that they are therefore the indi- 

 cations of the series of great geological phenomena which have 

 been manifested during the Jurassic age." H 



320. M. D'Orbigny has given to these ten stages names taken 

 chiefly from the places, where their mineralogical characters have 

 been most developed and observed. To avoid encumbering the 

 reader with a nomenclature so complex, we shall here designate 

 the stages according to their order of superposition, or what is 

 the same, their dates of deposition, beginning from the lowermost 



* D'Orbigny, Paleontologie, vol. ii. p. 419. 

 66 



