SEQUEL TO SYSTEMATIC GEOLOGY. 579 



country in which his types were found ; and this is 

 a term excellent in many respects; but one which 

 will probably not quite supersede " Transition," be- 

 cause, in other places, transition rocks occur which 

 correspond to none of the members of the Silurian 

 region. 



Though new names are inevitable accompani- 

 ments of new views of classification, and though, 

 therefore, the geological discoverer must be allowed 

 a right to coin them, this is a privilege which, for 

 the sake of his own credit, and the circulation of 

 his tokens, he must exercise with great temperance 

 and judgment. M. Brongniart may be taken as an 

 example of the neglect of this caution. Acting 

 upon the principle, in itself a sound one, that incon- 

 veniences arise from geological terms which have a 

 mineralogical signification, he has given an entirely 

 new list of names of the members of the geological 

 series. Thus the primitive unstratified rocks are 

 terrains agalysiens ; the transition semi-compact 

 are hemilysiens ; the sedimentary strata are yzemi- 

 ens; the dilvuvial deposits are dysmiens; and these 

 divisions are subdivided by designations equally 

 novel ; thus of the " terrains yzemiens," members 

 are the terrains dastiques, tritoniens, proteiques, 

 palceotheriens, epilymniques, thalassiques 6 . Such a 

 nomenclature appears to labour under great incon- 

 veniences, since the terms are descriptive in their 

 derivation yet are not generally intelligible, and 



6 Brongniart, Tableau r/r.v Terrains. 1829. 



PP2 



