268 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



history and will ultimately require its own nomenclature and classifica- 

 tion. 



It was Kirwan, 1 1 believe, who classified the rocks as " mountains," 

 translating the German word " gebirge" into mountain, instead of forma- 

 tion, as we should do now ; thus, " Steinkohlen gebirge," u grauwacken 

 gebirge," he called u Carboniferous mountains," " Grey walcke moun- 

 tains." 



Although the double sense is at once evident to us, the conception of 

 the German geologists expressed in applying the name " Gebirge" to a 

 geologic formation is not so far wrong as at first it would appear. It 

 was long ago learned that uniformity of nomenclature for mountains of 

 different continents is absurd. 



Although some relation exists between the position on the continent, 

 the distance from coast, and the size of the adjacent sea, as Guyot has 

 shown, geographic position of a mountain is the one thing distinguish- 

 ing it from all other mountains, and no consideration of similarity in 

 mountains dispenses with the necessity of separate names for every 

 local mountain range. Although covered from sight, and with our 

 present knowledge difficult to outline, it is altogether probable that 

 geologic formations are as completely separated geographically as are 

 mountains. Any classification of formations which does not recognize 

 geographic position as of primary importance is artificial, and in the 

 nomenclature regard for the geography must find a place if we would 

 be scientifically accurate. 



Having defined the geologic formations of a province, their correla- 

 tion with those of another province can be made only by means of the 

 fossil contents. This the experienced geologist has demonstrated. 



History shows that the correlations which have best endured the test 

 of time were made regarding formations whose structural and strati- 

 graphic features were elaborated independently of the correlation, aud 

 the correlation of which was based upon carefully collected ami exhaust- 

 ively studied fossils. The records of structure, composition, and strati- 

 graphic order, when based upon careful observation, are permanently 

 valuable contributions to knowledge, and their value is not increased 

 by attempts to fit them into some established classification upon scant 

 paleontoiogic data or hasty paleoulotogic comparison. 



The classification made by the field geologist should not be warped 

 to conform to any standard, not even that of the adjoining county, unless 

 there is structural evidence of identity of formations. Correlation by 

 physical means, i. e., inference from general dip, altitude, thickness, 

 when associated with likeness of composition, is practicable for short 

 distances and when made by experienced geologists, but even then the 

 determination is not absolute; contradictory paleontoiogic evidence in 

 the hands of an equally expert paleontologist should always be given 

 precedence. 



11 Geological Essays, " London, 1799. 



