Plate 36 



' 1. Smith's Mountain, North Carolina; fine octahedrite; Ni-Co 8.52 percent. Granular 

 kamacite showing a transformation structure of varying character in the three grains. 

 The structure at lower right resembles a martensitic iron-carbon structure in a low carbon 

 (e. g., 0.10 percent) steel water-quenched from the lower gamma-alpha range. Picral 45 

 seconds; X 150. U. S. National Museum. 



2. Bear Creek, Colorado; fine octahedrite; Ni-Co 7.88 percent (Jackson, 1867). Part 

 of a rounded "swollen" kamacite band with strongly marked transformation structure — an 

 example of the "hatched" kamacite of the older writers. Traces of the structure appear in 

 the kamacite bands on each side. Picral 75 seconds; X 30. 



3. Kenton County, Kentucky. Medium octahedrite; Ni-Co 8.49 percent. The kama- 

 cite shows varying forms of transformation structure. The irregular taenite lamellae are 

 dark by reason of incomplete transformation. Picral 25 seconds; X 150. 



4. Kenton County. Structure similar to that in the left portion of figure 3. The pat- 

 tern is very regularly oriented. Picrak25 seconds; X 150. 



156 



