236 Wisconsin Academy of Sciences, Arts^ and Letters. 



Class IV. Basis of Classification — Chemical Nature. 



Silicious. 

 Calcareous. 

 Ferruginous. 

 Carbonaceous, etc. 



Class V. Basis of Classification — Mineral Constitution. 



Quartzose. 



Micaceous. 



Pvritiferous. 



Garnetiferous. 



Staurolitic. 



Chloritic, etc. 



Class YL Basis of Classification — Lithological Character. 



Granitic. 



Basaltic. 



Dolomitic. 



Porphyritic. 



Trachjtric. 



Dioritic, etc. 



Class Yll. Basis of Classification.— Origin. 



Igneous, 

 Aqueous, 

 Metamorphic, 

 Pseudomorphic, 

 Eolian, etc. 



B. NOMINAL. 



Class I. Basis. — Physical Form of the Constituents, {Mainly.) 



] Pudding stone. 

 Conglomerates : > Gravel, (iLCoherent conglomerate). 

 ) Breccia. 



Grit, grit-rock, sand, sandstone, sandrock. 



Clay, mud, silt, earth, alluvium, soil, 



Till, 



Tufa, etc. 



