EXPLANATION OF PLATE 14 

 Fig. 1. Cast manganese steel. X 392. 



Eutectie and troostite in a groundmass of gamma iron. (W. S. Potter, Trans. 

 A. I. M. E., vol. L, p. 465.) 



Fig. 2. Nickel ore, Creighton Mine. X 608. 



Chalcopyrite and pentlandite in a groundmass of pyrrhotite. (Tolman and 

 Eogers, figure 36.) 



[252] 



