Lithological Nomenclature. 235 



effort to separate lithological terms into distinct classes, having 

 reference to the several different attitudes from which the char- 

 acter of rocks may be viewed, as physical, chemical, mineralog- 

 ical, petrographical ; and (2), the introduction of a series of 

 contractions, and a system of compounding terms, which shall 

 render lithological names at once specific, self-explanatory and 

 measurably quantitative. At the same time the mischievous im- 

 plications attached to prevalent terms, fashioned after those ap- 

 plied to definite mineralogical species, are avoided. 



Lithological terms are either adjective or nominal in character, 

 and a complete series of each would greatly facilitate expression. 



The following classification of terms, embracing mainly those 

 already in use, will make more clear the place and function of the 

 changes and additions proposed : 



Lithological Terms. 



a. adjective. 



Glass I. Basis of Classification — The Physical Nature of the Con- 

 stituents. 



f Conglomeratic. 



1. Fragmental. (Detri- j Sandy or arenaceous. 



tal, Clastic.) j Clayey or argillaceous. 



[Compact, etc. 



( Granular or phanero-crystalline. 



2. Crystalline. \ Crypto-crystalline. 



( Purpbyritic, (the above combined.) 



Class 11. Basis of Classification — The Structure of the Mass. 



Massive. 

 Schistose. 

 Shaly. 

 Slaty. 

 Laminated, etc. 



Class III. Basis of Classification — Coherence. 



Tenaceous, firm, compact, etc. 

 Incoherent, friable, uncompacted, etc. 



