G. K< Gilbert — Congress of Geologists. 441 



as we should thus lose the mnemonic connection of times with 

 corresponding terranes. I propose as a means of accomplishing 

 the end with the least inconvenience, that a set of time words 

 be derived from the terrane names by modifying the final syl- 

 lables. The time words should all have the same termination, 

 and that should differ from any terminations occurring in the 

 terrane names. I suggest for the ending of time words the 

 syllable al. With such a nomenclature Jurassic and Devonian 

 would denote only certain European rock systems, while Jural 

 and Devonal would denote periods of the standard time scale; 

 and we could speak of the Chico-Tejon series as partly Eocenal 

 and partly Cretaceal without seeming to imply the existence in 

 California of the Eocene and Cretaceous systems of Europe. 



A few minutes ago I opposed the differentiation of words by 

 terminations because it abrogated the power of indefinite 

 expression ; I now favor it for the same reason. It is well to 

 be indefinite as to the taxonomic rank of terranes while their 

 characters are imperfectly known, but it is not well to con- 

 fuse terranes with times. 



It is not to be assumed that a time scale adopted now as the 

 best possible will continue indefinitely to be the best possible; 

 the day will inevitably come when it can be improved. In the 

 fuller light of the future we may recognize as very unequal 

 periods that we now deem equivalent, and the possibilities of 

 defining pre-Cambrial periods are unlimited. Even now there 

 are announced beneath the lowest fossil-bearing terranes of the 

 Lake Superior region two systems of clastic rocks limited 

 above and below by great unconformities, and Irving demands 

 their recognition as a group, distinct from the Archaean. If his 

 voice is heard, the time scale will include an era between the 

 Paleozoal and the Archeal, and this era will supply the needs 

 of the systematist until great additions have been made to our 

 present knowledge of the older rocks. 



My only remaining subject is the representation of terranes on 

 maps by means of colors. At present no two organizations 

 and scarcely two individuals use colors in the same way, and 

 it is probably true that every organization and individual pub- 

 lishing many geologic maps has at different times employed the 

 same color for different terranes and different colors for the 

 same terrane. It results that the map user can gain no infor- 

 mation from the distribution of colors until he has studied the 

 legend ; before he can read a new atlas he must learn a new 

 alphabet. The advantage to be gained by substituting a. uni- 

 versal language for this confusion of tongues is manifest and 

 great, and has justified the application of much time and atten- 

 tion by the Congress and its committees. By a series of 



