﻿Huntington — Crystalline /Structure of Iron Meteorites. 291 



All the faces were polished and etched so that the plates 

 might be followed through their entire extent. On examina- 

 tion, it appeared that the majority of the plates, including even 

 the finest microscopic markings, followed the direction of the 

 octahedral faces. But there will be noticed in the sketch of 

 the octahedral face, that, in addition to the usual directions, 

 there appear certain plates which bisect the facial angle of the 

 octahedron. These plates, when followed over an edge on to 

 an adjacent face, were seen to be parallel to an octahedral edge, 

 showing that they must be dodecahedral instead of octahedral. 



Thus it at once appeared that the Widmanstattian figures 

 could not be solely characteristic of octahedral structure. 

 Furthermore, the Butler meteorite seemed to stand between 

 well- marked Widmanstattian figures and the finer lines dis- 

 covered by Neumann and shown by him to be parallel to cube 

 edges. Some of the Butler figures are coarse enough to be 

 classed unquestionably as Widmanstattian, that is, they show 

 the three varieties of iron distinguished by Keichenbach, which 

 he calls the Trias ; while others of the figures are almost micro- 

 scopic markings, in which distinct plates of kamacite and pies- 

 site cannot be made out even under the microscope. Between 

 these two extremes there is every gradation. The Butler mete- 

 orite has always been classed among the octahedral irons. We 

 come next to the Coahuila, which has been classed with the so- 

 called cubic irons. 



A large section of this iron, on being etched, showed innum- 

 erable fine lines, seeming at first sight as irregular as the mark- 

 ings on a chopping-block. When this section was examined 

 under the microscope, it showed all the characters of the Butler 

 figures, only a degree finer. On studying the directions of the 

 lines, they appeared to make every possible angle with each 

 other, but with a prevalence of right angles. The meteorite is 

 very compact, with usually no external 

 crystalline form, but it was found that on 

 one specimen, by quick blows of the ham- 

 mer, cleavage masses could be broken 

 away. One of these cleavage masses is 

 shown, of twice its original size, in fig. 5. 

 It has the well-known form of the cube 

 twin, described by Tschermak* as typical 

 of the Hauptmannsdorf iron, but with 

 this difference, that the cube in this case is 

 modified by the octahedron. On polish- 

 ing and etching the crystal faces, the lines 

 appeared so fine as to be for the most part ^ c 



indistinguishable by the naked eye, but Coahuila, Mex. 



* Akademie der Wissenschaften Wien, lxx, 449. 



