56 



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



magnifying glass the nature of the minerals composing the rocky part 

 of the stone cannot be determined, but tin-white metallic particles, 

 abundantly present, can easily be distinguished ; one also sees small, 

 irregularly shaped pores or cavities, some partially filled with a brown 

 ferruginous substance. After the fragments had lain untouched for 

 some time in a closed box, there were also observed under the magni- 

 fying glass, on parts of the fresher-looking surfaces, very small drops 

 of a dark brown fluid, which, however, spread and dried up before a 

 micro-chemical test could be made. This fluid seems to originate 

 the ferruginous glaze before mentioned, and may possibly consist of 

 chloride of iron. 



Microscopic Character of the Stone. 



For the purpose of microscopic examination, seven thin sections 

 were available, which proved the stone to belong to the " chondrites," 

 or, according to Wadsworth, to the variety " saxonite " of the peri- 

 dotites, and to be composed of the following minerals : — Olivine, 

 enstatite, glass, a substance resembling glass, nickel-iron, troilite, 

 and black opaque grains, probably magnetite. All the sections are, 

 besides, more or less strongly flecked and stained with brown hydrous 

 ferric oxide, originated, no doubt, through oxidation of the iron 

 minerals. 



Olivine. — This is the predominant mineral, and has a faint green- 

 ish-yellow colour in common transmitted light, but shows brilliant 

 polarisation-colours between crossed nicols. It appears partly in 

 well-defined chondrules, partly in larger and smaller grains of crystal- 

 like or irregular outlines, closely packed together — the larger ones in 

 some cases much, in others little, fractured ; also in columnar bodies, 

 some short and stout, others long and narrow, and sometimes curved, 

 and all generally much fractured transversely — most fractures running 

 at right angles to the length of the crystals, others obliquely, and 

 from both sides. The extinction between crossed nicols of these 

 columnar bodies is mostly parallel to their longitudinal extent, in cases 

 more or less oblique, and it is rarely quite complete throughout, as 

 small brightly coloured specks are generally observable here and 

 there within the darkened body. The chondrules show various modes 

 of internal structure. One kind is very fine granular, of dull-greyish 

 or dusty aspect, and extinguishes pretty uniformly throughout, only 

 some promiscuously distributed bright grains shining out. Around 

 these chondrules large clear olivine grains, sometimes all of uniform, 

 sometimes each of independent, optical orientation, are frequently 

 arranged ring-like, and so that the divisional joints stand rudely 

 radial (see figs. 3 and 6). This radial arrangement of the joints 

 respecting grains is also observable, however, around groups of 

 several larger grains as centre. A rare and pretty variety of the 



