OP ARTS AND SCIENCES. 



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separated from the groundmass by a thin layer of iron rich in nickel, 

 called by Reicheubach Baudeisen or Taenite. This material is not 

 readily acted upon by acid, and therefore appears on the etched surface 

 as a bright silvery line along the edge of the kamacite plates. In 

 some meteorites, as in the Cocke County and Sevier County, it occurs 

 in sufficient mass to be easily separable from the plates in the form of 

 a thin elastic foil, while in others it almost wholly disappears. The 

 thin plates of " bandeisen " resist the action of oxidizing agents, as 

 they resist the action of dilute acid, so that, when the surface of the 

 meteorite becomes disintegrated by air and moisture, these plates not 

 unfrequently become loose, and are easily separated. Dr. Lawrence 

 Smith analyzed the material of some plates thus obtained from the 

 Sevier County meteorite, and found in them 27% of nickel. The 

 groundmass consists of what Reichenbach calls Fiilleisen, or Plessite. 

 In the present case, the latter is filled with very thin plates, or 

 " combs," in general following the octahedral directions and appear- 

 ing to be a subsequent crystallization, as if the larger plates had first 

 shot through the mass when in a liquid state, and then, as the interior 

 portions solidified, these also crystallized more or less perfectly, but 

 forming smaller and smaller plates. 



Figure 2 shows, double the natural size, one face of a very perfect 

 octahedron broken out from the Putnam County meteorite. This 



iron appears by oxidation of the surface 

 to break up into octahedrons aud acute 

 rhombic prisms. The octahedron rep- 

 resented in Fig. 2 was so loose in its 

 structure that it was necessary first to 

 mount it in pitch before grinding the 

 face in order to prevent the plates from 

 splitting off. Here the character is much 

 the same as in the previous one, except 

 that the plates are smaller, and at the 

 points a, h, and c the iron is perfectly 

 granular, showing no signs of crystal- 

 lization. Moreover, the groundmass, 

 instead of containing the combs above mentioned, has been broken up 

 by a series of irregular cracks into coarse grains, very much like a 

 mass of crackled glass. Another meteorite which most beautifully 

 illustrates the octahedral arrangement is the Tazewell (Claiborne 

 Co.) iron, Fig. 3. Here the figures brought out by etching are very 

 sharply defined, but are so small that, in some parts of the field, it 



Fig. 2. Putnam Co., Georgia. 



