﻿286 Huntington — Crystalline Structure of Iron Meteorites. 



very large collection of Harvard College, which, since the 

 acquisition of the collection of the late Dr. J. Lawrence Smith, 

 has representatives of all the characteristic meteorites of this 

 class. The writer has been familiar with this collection since 

 it was acquired by the college, and, in examining the specimens 

 from time to time, he has been struck by the indications of 

 c^stalline form which many of them present. These appear 

 like roughs octahedrons, and their irregular faces present the 

 most striking similarity to cleavage planes, although in some 

 cases the surfaces are covered and the edges rounded by a 

 fused crust. On further examination, it appeared evident that 

 the surfaces in question must be true crystalline faces, for not 

 only were these faces parallel to planes of fracture as indicated 

 by rifts through the mass, but they also stood in a definite rela- 

 tion to the Widmanstattian figures. Moreover, rifts of fracture 

 were common when no external crystalline form could be made 

 out, and hence came the idea of using the cleavage faces as 

 planes of reference in studying the crystalline structure of the 

 iron meteorites; and the plan was formed to grind, polish and 

 etch surfaces either parallel to the cleavage planes or in a 

 known position towards them, with the hope that it might thus 

 be possible to determine with certainty the relations of the 

 crystalline plates whose cross-sections form the Widmanstattian 

 figures. This was in general the plan of the investigation 

 whose results are here given. 



The most striking example of such a rude cleavage form as 

 has been described is a mass of the Franklin County (Ken- 

 tucky) iron weighing 7,260 grams, which shows all the planes 

 of an octahedron, inclined to each other at the regular octa- 

 hedral angle (109° 28') as nearly as the uneven surfaces of the 

 faces would admit of measurement with an application goni- 

 ometer. This large, unique, isolated octahedron, of massive 

 iron, measures seven inches in its longest dimension, and one 

 of the triangular faces distinctly outlined measures over four 

 inches on each edge. Another face, still more distinctly 

 marked, measures three inches on each edge. At various points 

 there are triangular depressions or reliefs conforming to the 

 general outline, features which are so characteristic of large 

 crystals ; and there are also numerous rifts parallel to the octa- 

 hedral faces. A large part of the surface is covered with a 

 crust, and, on the basis of the usual interpretation of meteoric 

 phenomena, it is obvious that this crystal is the fragment of an 

 iron meteorite broken up after entering the atmosphere, but 

 while still moving rapidly enough to produce a melted crust 

 over the surface of fracture. 



Another example in the Harvard collection of external octa- 

 hedral form is a specimen of the Carthage (Smith Co.) iron. 



