PLATE 28. 



Micro-metallography. 



A SPIEGELEISEN x 45 

 B DITTO x 500 



A B 



Objective Zeiss Micro-Planar, Zeiss 16 mm. Apo. 



25 mm. 



Ocular None. Zeiss Comp. x 12. 



Illuminator ... Cover-glass reflector. 



Illuminant ... Liliput 4 amp. arc. 



Aux. Condenser Biconvex lens, convergent beam, directed 



on to cover-glass reflector. 



Plale Imperial N.F. 



Exposure ^ sec. 15 sec. 



The specimen was polished, and etched with saturated solution of 

 picric acid in absolute alcohol to exhibit its structure. Spiegeleisen 

 is a highly crystalline variety of white cast-iron containing manganese. 



Photographed with the apparatus of Fig. 65. using a cover-glass 

 reflector. The aperture of the condenser restricted by an iris 

 diaphragm to prevent haze when using the higher power objective. 



Photos. W. B. R. \Tofollowpage2QO. 



