CHAPTER III. 



NOMENCLATURE EMPLOYED IN THE DESCRIPTION OF THE FOR- 

 MATIONS. 



Several considerations are to be borne in mind relative to geologic 

 nomenclature : 



(a) The name in itself is nothing unless it conveys to the mind a 

 clear impression of what it refers to and enables the student to make a 

 correlation between its entity and some other entity that has another 

 terminology. 



(b) Priority of discovery and naming should be sustained by the proof 

 of the accuracy of the original observations, the latter to be judged by 

 the testimony of the formations in the areas where they were first made. 

 If the original proposer of a name bases it upon such errors of observa- 

 tion and interpretation that subsequent observers can not verify his 

 work, and the name can be used only by dropping a name proposed as 

 the result of accurate observation aud definition, the latter should be 

 retaiued and the law of priority should not be used to bolster up an in- 

 definite term. 



(c) Long use of, and the general acceptance of, a well defined term by 

 the scientific world gives that term a standing that even the claims of a 

 half understood, badly defined term supported by priority should not 

 displace. This may be called the law of usage. 



(d) From the fact that all the strata of the geologic series do not ex- 

 ist in any one geologic province and that unconformities between differ- 

 ent portions of them are not contemporaneous in all provinces, it neces- 

 sarily follows that the rock series of any one geologic province can not 

 possibly be the chronological equivalent of the rock series of other 

 provinces. Overlappings of series of different chronologic age must 

 occur, and it is therefore impossible for any one geologic province to 

 afford a nomenclature that is applicable to the geologic provinces of 

 the entire world or to the entire geologic series. 



(e) Each geologic province should have a nomenclature denoting by 

 name each formation contained in it and, if necessary, the names to be 

 applied to the groupings of the formations; but, if practicable, the 

 formations and the grouping of formations should be referred to some 

 position within the larger composite groups. For instance, the Pots- 

 dam standstoneof New York, the Saratoga County limestone, and the 

 Dutchess County limestone are lithologically distinct formations, but 

 they are grouped under the Upper Cambrian terraue as a portion ot 

 the Cambrian group. 



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