60 



Prof. G. H. F. Ulrich. On a Meteoric Stone 



dotting and cross-shading. Figs. 1 — 5 are magnified 25 diameters, 

 fig. 6 is magnified 50 diameters. 



Fig. 1. — This shows a nearly circular chondrule — the finest seen 

 in any of the sections. It consists throughout of olivine : the upper 

 very fine-granular part is somewhat dull or dusty, the lower coarse- 

 granular part is clear, but some of the cracks are filled with dull- 

 brown ferruginous matter. Around the circumference of the fine- 

 granular part there is a rim of small clear grains of olivine, the 

 divisional joints of which stand mostly radial ; and around this 

 rim again, also surrounding the coarse- granular part, there is a 

 border of small, black grains of magnetite. The fine-granular part 

 and its encircling rim of radial grains, as well as most of the 

 grains of the coarse -granular part, have the same optical orientation, 



Fig. X, 



OCL 



as they show pretty uniform simultaneous extinction between crossed 

 nicols. In one of the grains of the coarse-granular part at the point 

 indicated by a dotted line and the letters (pa) an optic axis is visible 

 in convergent polarised light. What is seen outside the chondrule con- 

 sists of an aggregate of larger and smaller grains, and several very 

 fine granular patches of olivine showing aggregate polarisation and 

 enclosing a number of particles of nickel-iron and dark grains, some 

 of which, of dull-bronzy lustre, may be troilite. The two large parti- 

 cles of nickel-iron near the upper edge of the figure are so connected 

 by and with a dull dark substance as to render it very probable that 

 this substance is also nickel-iron, which, through oxidation, has lost 

 its metallic lustre. 



Fig. 2. — This shows on the lower margin, a little to the right, part 

 of a large chondrule of enstatite rendered fibrous by fine eccentric 

 striae, and rather densely filled with fine dark dust. Between crossed 

 nicols on rotation of the stage its polarisation colours are of a low 



