242 Wisconsin Academy of Sciences, Arts, and Letters. 



Hematite — Hem., or hema. 



Menaccanite — Menac, or menacca. 



Tourmaline — Tour., or tourma. 



Graphite— Graph., or graphi. 



Apatite — Ap., or apa. 



Andalusite — Andal., or andalu. 



Cjanite — Cj., or C)^an. 



Sericite — Seri., or seric. 



Zircon — Zir., zirc, or zirco. 

 In the combination of these it is suggested that the leading 

 constituent stand first, and that the remaining constituents follow 

 in the order of importance. In crystalline rocks there will often 

 be present minerals in small and varying quantities, which it will 

 be neither convenient nor desirable to include in the compound 

 name of the rock, but which should be regarded, as they com- 

 monly are, as accessory minerals. There may be little philo- 

 sophical basis for this distinction, since the rock is at best but an 

 aggregate, and is what it is by virtue of the total aggregation, and 

 not by virtue of any definite composition, as in the case of a 

 mineral or chemical compound. Kevertheless, these minor min- 

 eral constituents do not, in the main, represent any distinctive 

 condition in the formation of the rock, but rather some of those 

 accessory circumstances common to a wide range of rock-forma- 

 tions. They are, therefore, geologically incidental, rather than 

 essential, conditions, and their products may, therefore, be omitted 

 from the compound name and classed as accessory minerals, and 

 as such receive attention in exhaustive descriptions, without 

 burdening the more general discussions. It will of course be 

 within the discretion of each writer, in the case of a given rock, 

 to decide what are its essential and what its trivial constituents. 



In this system no uniform terminal syllable is proposed. It may 

 be doubted whether lithologists will take kindly to this innovation, 

 since it is at variance with the prevalent custom of terminating 

 rock names with an ite or an yte, after the fashion of mineralogical 

 terms. A grave objection to the usage, however, arises out of the 

 very fact of this imitation, since it implies, in the rock-aggrega- 

 tion, something of the same deSniteness of constitution that the 

 mineral possesses ; and this, I believe it is universally conceded, 



