530 HISTORY OF GEOLOGY. 



a descriptive word has become permanent in a case of this kind ; and, 

 in imitation of it, Poecilite (from -roixiXoj, various, (has been proposed 

 by Mr. Conybeare* as a name for- the group of strata inferior to the 

 oolites, of which the Variegated Sandstone (Bunter Sandstein, Gres 

 Bigarre,) is a conspicuous member. For the s'eries of formations which 

 lies immediately over the rocks in which no organic remains are found, 

 the term Transition was long used, but with, extreme ambiguity and 

 vagueness. "When this series, or rather the upper part of it, T/as well 

 examined in South Wales, where it consists of many well-marked 

 members, and may be probably taken as a type for a large portion of 

 the rest of the world, it became necessary to give to the group thus 

 explored a name not necessarily leading to assumption or controversy. 

 Mr. Murchison selected the term Silurian, borrowed from the former 

 inhabitants of the 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," because, in other places, transition rocks 

 occur which correspond to none of the members of the Silurian region. 

 Though new names are inevitable accompaniments 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 prin- 

 ciple, in itself a sound one, that inconveniences arise from geological 

 terms which have a mineralogical signification, he has given an entire- 

 ly 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 yzemiens ; 

 the diluvial deposits are clysmiens ; and these divisions are subdivided 

 by designations equally novel ; thus of the " terrains yzemiens," mem- 

 bers are the terrains clastiques, tritoniens, proteiqites, paloeothe- 

 riens, epih/mniques, thalassiques* Such a nomenclature appears to 

 labor under great inconveniences, since the terms are descriptive in 

 their derivation, yet are not generally intelligible, and refer to theo- 

 retical views yet have not the recommendation of systematic con- 

 nexion. 



Report, p. 379. " Brongniart, Tableau des Terrains, 1829. 



