Studies for Students. 



THE MAKING OF THE GEOLOGICAL TIME-SCALE. 



A CRITICAL examination of the nomenclature applied to the 

 several divisions of the geological scale reveals a strange mixture 

 of names, the reason for which is not evident to modern students 

 of the science. In the list of system-names we find Carboniferous 

 and Cretaceous, indicative of mineral characters, associated with 

 Tertiary and Quaternary, meaning rank in some undefined order 

 of sequence. The presence of these terms is no less mysterious 

 than the absence of grauwacke and old -red sandstone, and pri- 

 mary and secondary, which were originally included. Triassic is 

 the name of another system and records the three -fold division 

 of the system of rocks to which it was applied; and Devonian, the 

 name of another, reminds us of the county in England in which 

 its rocks were first named. Observing these things, one is 

 tempted to call in question the reliability of a systematic classi- 

 fication so heterogeneously compounded. 



Although the older living geologists can remember back 

 almost to the beginnings of the science, those who now are begin- 

 ning their study of geology may find profit in examining the 

 foundation principles, and the systems which have been devised, 

 and have led to the construction and belief in the present classi- 

 fication — a classification, the adoption and unification of which has 

 been thought worthy of the organization and continuance of an 

 international Congress of Geologists. It is needless to call atten- 

 tion to the necessity of some systematic classification of geolog- 

 ical formations, but as a foundation for the scientific study of the 

 history of organisms there is need of a time -scale running back 

 into the pa^t, the degree of accuracy of which is known as Well 

 as the extent of its unreliability. In early attempts to classify 



