Art. IX. — On the Nomenclature of Geological Age. 



By G. B. PRTTCHARD, 



Lecturer in Geology, etc., at the Working Men's College ; 



Acting Lecturer in Geology, Mineralogy, and Metalkirgy at the 



Melbourne University. 



[Eead before Section C of the Australasian Association for the 

 Advancement of Science, 12th January, 1900.] 



As a teacher of geology I find one aspect of the subject which 

 is continually causing difficulties and confusion to the students, 

 is the very loose and indefiTiite use of the terms indicating 

 geological age. In the present paper I hope to be able to point 

 out a few of the inconsistencies and contradictions that have 

 come under my notice in the course of my work, and to show the 

 very peculiar state we have arrived at with regard to our Time 

 Scale for the Australian Colonies. 



Although many of us have been taught to recognise a general 

 table of Geological Divisions of the Time Scale as of general use 

 and world-wide application, we soon find that such is really not 

 the case, and as Professor Scott has rightly remarked,^ " The 

 method of making the divisions and subdivisions of geological 

 time is not yet a fixed one, and there is much difference in the 

 usage of various writers." In the first place it seems sufficient to 

 recognise the three divisions — Palaeozoic, Mesozoic, and Cainozoic, 

 of the Geological Record, or as an alternative — Primary, 

 Secondary, and Tertiary, but even this is not consistently 

 adhered to, for we find the term of Tertiary much more frequently 

 used than the term Cainozoic and associated with the terms 

 Palaeozoic and Mesozoic. We find some authorities recognising 

 five main divisions of the Geological Record,' that is in addition 

 to the above, the oldest division has been variously referred to as 

 Pre-Cambrian, Archaean, Azoic, Eozoic, or Proterozoic, and the 

 youngest as Post-Tertiary or Quarternary. Is tliere any necessity 



1 An Introduction to Geology, by Professor W. B. Scott, p. 354. 



2 Text Book of Geology, by Archibald Geikie, 3rd ed., p. C80. 



