Plate 76 



1. Helt Township, Indiana; coarsest octahedrite; no analysis. A lamella of taenite 

 broken and displaced along the planes of Neumann lines. The meteorite is very small 

 and flakelike in shape, showing throughout incipient alteration by brief heating during 

 atmospheric flight. In this field the alteration was not sufficient to obliterate the Neumann 

 lines, but has formed a zone of granulation along the taenite lamella. A small rhomboidal 

 schreibersite body indents the lamella. Picral; X 60. 



2. Helt Township. Part of the area shown in figure 1 at higher magnification. Owing 

 to the ductility of the taenite, the shearing movement rounded the outside corners slightly 

 and left a thin layer connecting the separated portions of the lamella. The new grain bound- 

 aries, evidence of the partial alteration by heat, are in conformit}- with the displaced struc- 

 ture, showing that deformation occurred before the alteration was accomplished. In the 

 narrow zone of granulation the Neumann lines are parth" obliterated. Picra! 5 seconds; 

 X 300. 



3. New Baltimore, Pennsylvania; granular hexahedrite; Ni-Co 6.74 percent. The 

 striated band marking a dislocation is about 2 cm. long, lying within one of the very large 

 grains of this iron. It becomes less distinct toward each end, merging into the confused 

 general structure. In many other places this iron bears evidence of more or less distortion, 

 Neumann lines being bent and in places showing the effects of a shearing movement similar 

 to that here shown. Neumann lines are sometimes clear, but mostly are blurred with a 

 black component which in appearance suggests an effect of cold working .due to movements 

 within the mass, but which actuallv is not due to that cause (see pi. 77). Picral 80 seconds; 

 X 30. 



4. New Baltimore. Part of the area shown in figure 3 at higher magnification. Picral 

 30 seconds; X 150. 



196 



