﻿296 Hu n t ingto n — Crystalline Structure of Iron Meteorites. 



stattian figures as well as the finest Neumann lines are inter- 

 sections of planes of crystalline structure, which may be 

 parallel to faces of the octahedron, the dodecahedron, or the 

 cube. 



Of course it is not maintained that there is not a marked 

 distinction between characteristic Widmanstattian figures show- 

 ing all the features of the three kinds of iron, and typical 

 Neumann lines as exhibited by the Hauptmannsdorf meteorite, 

 but only that both are an outgrowth as it were of the same 

 type of crystallization. 



The Germans strongly insist on the divisions of the trias of 

 Reichenbach, and describe the features of kamacite, taenite and 

 plessite as if they were essentially different substances, instead 

 of merely different conditions of a nickeliferous iron ; and the 

 only evidence we have that there is any material difference of 

 composition is based on an analysis cited by Reichenbach* of 

 the so-called tsenite plates, which he had mechanically sepa- 

 rated from the Cosby Creek iron, and which were found to con- 

 tain 13 '8 per cent, of nickel, while the mass as a whole only 

 contained 9*8 ; and, on this ground, it is assumed that kama- 

 cite consists of a purer iron. As stated above, Dr. Lawrence 

 Smith found in plates obtained from the Sevier County iron, 

 which is closely allied, if not identical, with the Cosby Creek, 

 27 per cent of nickel. This supposition would harmonize with 

 our idea of the manner in which crystallization takes place. 

 For though a substance in crystallizing may include foreign 

 substances, still crystallization is a purifying process. Hence, 

 as the molten metal cooled, there would be a tendency for the 

 pure iron to crystallize first, thus forcing back, as it were, a 

 less pure material, which would solidify subsequently ; and 

 the natural alternation of such stages, during a very slow pro- 

 cess of crystallization, would result in a succession of plates of 

 comparatively pure metal interlaminated with a richer nickel- 

 iron alloy. 



This theory is strongly supported by the structure of the 

 Pallasites, where the iron occurs surrounding masses of olivine. 

 Here, as Reichenbach has so beautifully shown,f the silicate 

 grains are first surrounded by a deposit of kamacite, and the 

 trias does not appear till this layer of the purer iron has been 

 deposited. 



Moreover, Tschermak has shown,;}: in regard to artificial 

 irons, that pure iron tends toward a cubic crystallization with 

 markings similar to the Hauptmannsdorf meteorite, while im- 

 pure iron, like cast-iron, frequently shows imperfect octahe- 

 drons and a scaly structure, not unlike that of many meteorites, 

 and this becomes very striking in the so-called spiegeleisen. 



* Poggendorff's Annalen, cxiv, 258. f Ibid., p. 99. 



\ Akademie der "Wissenschaften, Wien, II, lxx, 44*7. 



