Feb., 1906. The Shelburne Meteorite. 15 



continued treatment with strong nitric acid the nickel-iron was en- 

 tirely dissolved out and the troilite was left free. It was found 

 to be chiefly in the form of small elongated and flattened nodules and 

 plates, showing a tendency to faceting at some points, but with no 

 determinable planes. One of these nodules had a length of 3 mm. 

 The separation between these nodules and the nickel-iron seemed 

 complete, there being no intimate intergrowth of the two sub- 

 stances. The troilite was of dark bronze-yellow color, non-magnetic 

 and easily fusible to B. B. a magnetic globule. 



The microscopic characters of the meteorite have been quite 

 fully described by Borgstrom, and the features which he points 

 out are essentially duplicated in the sections before the writer. 

 The chondritic structure of the meteorite is very marked, and the 

 chondri exhibit a variety of structures. Especially well represented 

 are those made up of parallel lamellae of chrysolite and glass. 

 These lamellae run in different directions in different chondri. In 



Fig. 2. Diagrammatic representation of arrangement of chrysolite lamellae in 

 chondri of Shelburne meteorite. 



some they are all parallel and, together with the border of the chon- 

 drus, extinguish simultaneously. In others they may be found run- 

 ning in two or more directions, in which case those lamellae which 

 are parallel extinguish simultaneously, but extinctions are different 

 for the different groups. In the accompanying diagrams, Fig. 2, 

 are represented some of the arrangements of lamellae observed. 

 The first diagram shows a simple single arrangement, the second 

 two sets of lamellae meeting at angles of 135°, and the third prac- 

 tically two sets of lamellae meeting at angles of 90 , although 

 on one side the lamellae are somewhat bent. Extinction in all these 

 forms is parallel to the long axis of the lamellae. The width 

 of the lamellae in the chondri of this character is remarkably 

 uniform, and is about .01 mm. The diameter of the 

 chondri themselves is from 1 to 1.5 mm. When the individual 

 lamellae are studied with a high magnifying power their apparent 

 continuity in the direction of length resolves itself into two 



