﻿Huntington — Crystalline Structure of Iron Meteorites. 301 



used in illustrating this paper, and it will be seen that the re- 

 semblance is very close. The analogy here is far more than 

 superficial, and shows, as we conceive, the mode of action by 

 which the Widmanstattian figures were produced. This will 

 be evident if it is borne in mind that the figures on the mica 

 plate are also sections of planes of crystalline growth on which 

 the particles of oxide of iron eliminated during the process 

 were deposited. Of course, the mere resemblance in the out- 

 line of the two sets of figures is accidental, and arises from the 

 circumstance that the planes of crystalline growth of musco- 

 vite mica are parallel to a rhombic prism of sixty and one hun- 

 dred and twenty degree angles, the right section of such a 

 prism being similar to the section of a regular octahedron par- 

 allel to one of its faces. 



11. 



Mica. — Chandler's Hollow, Delaware. 



The conditions of the plessite which fills the cavities between 

 the crystalline plates of iron meteorites also present features 

 which are especially characteristic of the crystallization of 

 alloys. Sometimes the space is packed with small crystalline 

 plates parallel to those of the external form, the combs already 

 mentioned, shown in fig. 1. Again the material is granular, as 

 shown at a ) b and c, fig. 2, or again divided into polygonal 

 masses as shown in the same figure. Similar features in the 



