114 G. H. Kinahan — Classification of Rocks. 



Fig. 5a. — id. Enlarged. 



„ 7. — Funis cancellatus, J. S. G. ; Gault. Author. 

 ,, la, lb. — id. Enlarged. 



„ 8. — Pyrgiscus Gaultinus, J. S. Gr. ; Gault. Craven. 



„ 9, 10.— id. Gault. Author. 



„ 9^. — Apex enlarged. 



„ 9^. — Ornamentation enlarged. 



,, 11, 11«. — Brachpstoma anffularis, Seelej ; Gault. Author, 



„ 12, 13, 13a. — Itissoina incerta, d'Orb. 



,, 14, 14«, 15. — Hissoina Sowerbii, J. S. G. 



(To be concluded in our next Numher.J 



III. — On the Classification and Nomenclature of Eocks. 

 By G. H. Kinahan, M.R.I. A., etc. 



IN a paper on the above subject, that appeared in the Geological 

 Magazine for December, 1875 (p. 583), the author, Mr. S. AUport, 

 F.G.S., objects to the introduction of additional rock names. With 

 this observer I agree that there are many ingenite rock names which 

 it would be satisfactory to get rid of; seeing many varieties and sub- 

 varieties of rocks to which names are given have no permanent 

 characters ; while in numerous cases the same rock is called by different 

 names. Still, as a geologist, I would suggest, that in some cases 

 new names are absolutely necessary, if we would impart our increas- 

 ing knowledge to the general public; for instance, among the 

 granitic rocks, the subject that has led to Mr. Allport's remarks. 



The granitic rocks at the present time are in a state of confusion. 

 Among the newer granitic rocks, some are called granites, while 

 others have been classed among the volcanic rocks ; besides, some 

 eminent geologists seem to be of opinion that all granites are of 

 nietamorphic origin, while others suspect they are all intrusive. 



This state of things will continue until these rocks are grouped, 

 not only in accordance with their origin, but also in relation to 

 their geological ages. To do this some new names will be neces- 

 sary ; and if such names were generally adopted, any one reading 

 a description of a country or district would be at once aware what 

 was the age and origin of the different rocks. For instance, if 

 Nevadite was the universal name for the elvanites, or passage rocks 

 between trachytes and normal granite, it would save a great deal 

 of repetition while describing many igneous districts. Similarly 

 with granites of metamorphic and intrusive origin : if they had 

 distinctive names, and were coloured differently on the geological 

 maps, there would not be the confusion that at present exists. 



On the Geological Maps of the Geological Survey Prof. Eamsay 

 has introduced distinctive colours respectively for the bedded and 

 intrusive igneous rocks, so that now the maps tell their own tale; 

 and the granitic rocks might be treated similarly. 



As I have pointed out in another place (Handy Book of Rock 

 Names), a reform is very necessary in rock nomenclature. This, 

 however, cannot be effected by one individual unless he be a 

 perfect field geologist, mineralogist, chemist, and microscopist. To 

 me, therefore, it appears that it ought to be done by a committee 



