U S GEOLOGICAL SURVEY 



MONOGRAPH XXVIII, PL 



I'll'.. 1. 



flO. 2. 



FIG. 3 



FIG 1. GRUNFRITIC \L\GNETJTE- SCHIST, 

 FIG. :i. FERni'GINOUS SLATE. 

 FU; .■J.FKRRl'GINOUS SLATE, 



