Smithsonian Report, 1951.— ZapfJe 



Plate 2 



1. Fractograph of a tough steel suitable for such construction as ship plate. The indi- 

 vidual grain is very small, causing fracture to change its path much more frequently as it 

 jumps from grain to grain; and the microscopic path through the grain itself is rough and 

 tortuous, as illustrated visually by this coral-like pattern of toughness. Magnified 1,000 

 times. 



2. Fractograph of a steel which, in contrast to that in figure 1 above, lacks toughness and 

 is unsuited for such applications as ship plate. The facet of this individual grain is com- 

 paratively smooth, showing much less interruption of the progress of fracture than in 

 the previous figure. Aiagnified 1,000 times. 



