46 Correspondence — Mr. W. 0. Crosby. 



ceased to connote what the author of the term intended by it, is quite 

 a minor question ; and I was so completely satisfied with Professor 

 Hull's surrender of the argumentum ad rem that I did not cai'e to lay 

 myself open to tlie charge of prolonging the discussion upon a col- 

 lateral issue. In appealing to the English sentiment of an audience 

 composed mostly of people who could scai'cely be expected to be 

 familiar with the question in all its ramifications, it was of course 

 not difficult to obtain an expression of opinion in favour of the 

 retention of the name Permian on that ground. But when we come 

 to consider the rival claims of connotative and geographical names of 

 groups of strata, a question of principle, rather than one of opinion, 

 is raised. For individual formations (pace the International Com- 

 mission) geographical terms are probably upon the whole preferable, 

 except in certain cases (e.g. ' Bunter,' ' Keuper '), in which the 

 general uniformity of character of a formation over a very large 

 area renders the difficulty of naming it from any locality very great. 

 In the main, however, the instincts of English geologists, which 

 have led them to give geographical names for the most part to single 

 formations, have led them at the same time to show a preference for 

 connotative names for the larger groups of strata. Thus, taking any 

 authoritative table of the British series, such as that in the excellent 

 Geological Chart of Prof. Morris, the preponderance is nearly three 

 to one in favour of connotative names for the more comprehensive 

 groups, as the following lists show : — 



Connotative Names. 

 Eecent. 



Pleistocene : Quaternary. 

 Pliocene. 

 Miocene. 



Eocene : Oligocene. 

 Cretaceous. 

 Oolitic. 

 Lias. 



Trias : New Eed Sandstone. 

 Dyas : Magnesian Limestone. 

 Carboniferous. 



Old Eed Sandstone. 

 Archijean. 



Geographical Names. 



Jurassic. 



Permian. 



Devonian. 



Silurian. 



Cambrian. 



Laurentian. 



The argument then in favour of the retention of the name 

 'Permian' (as against, e.g. that of ' Dyas ') is based on no logical con- 

 sistency with established geological nomenclature. It is an excellent 

 local name for the Russian series, but as a general term for the 

 European series it is highly misleading. A. Irving. 



Wellington College. 



OEIGIN OF CONTINENTS. 

 Sir, — My article under the above title, in the June Number of 

 the Geological Magazine, is criticized b}'^ Prof. Le Conte, in the 

 November Number, in a way that implies some misconception of my 

 position. My arguments were directed chieflj'^ against Prof. Dana's 

 theory, and only incidentally against that held by Prof. Le Conte, 



