1 1 I Prof. Maskelyne a?id Dr. Lang's Miner alogical Notes. 



like appearance seen when the crust of an aerolite has become 

 accumulated. This is most the case on the end of the meteorite. 

 It is thick and of a dull lustre, and there is no evidence of suc- 

 cessive formation in different parts of it. 



In structure the Nellore aerolite may be described as composed 

 of a friable and porous, pale bluish-grey ground-mass, very much 

 stained in patches by ferric oxide, and containing many small 

 semiopake, occasionally grey, but often greenish black irregu- 

 larly formed spherules, and also much granular iron distributed 

 pretty evenly in medium-sized particles, with a few larger ones 

 scattered at greater intervals. Meteoric pyrites is also seen 

 associated with the iron to the amount of about one-third its 

 bulk, and occasionally also minute particles Of a yellow mineral, 

 which is probably iron pyrites. There is also a little of a black 

 mineral which appears to be chromite. Examined more closely 

 by the microscope, the magma of this aerolite is found to be 

 formed of distinct crystals and crystalline aggregates of minerals, 

 the latter forming often a fine grey sort of network in which the 

 former are set. This aggregated granular but crystalline mineral 

 is like one which forms an important feature in Bachmut and 

 the aerolites of its class, in which it is seen surrounding and 

 entangling as in a network the other minerals. It owes its grey 

 hue sometimes to microscopic particles of iron and often to minute 

 fissures, among which what appear to be hollow bubbles without 

 liquid in them are in Nellore occasionally to be discerned. 



The crystals which are suspended in this ground-mass are of 

 different kinds. The most frequent is a mineral with but little 

 cleavage, and that parallel to the planes of polarization, which 

 doubtless consists of olivine. There are also present minerals 

 similar in general appearance and characters to the last, but 

 exhibiting a greater amount of cleavage, and that in directions 

 diagonal to the prismatic outlines of the crystal and oblique to 

 the planes of polarization, though the angles vary with the direc- 

 tion of the section. The directions of the planes of polarization 

 in these minerals usually indicate the prismatic system as being 

 probably that of this form of mineral. But a few cases occur in 

 which a mineral is seen the system of which does not seem to be 

 prismatic, as both the symmetry of the crystal (the section of 

 which generally affects the form of a rhomboid) and the direc- 

 tions of the planes of polarization suggest an oblique or anorthic 

 form. This latter mineral is possibly a felspar, as its crystal 

 generally presents itself in juxtaposition with another similar 

 crystal, evidently, from the different directions of its planes of 

 polarization, twinned with it. The former mineral will perhaps 

 be found to consist of Enstatite, the prismatic magnesian augite 

 (if it may so be termed), for our acquaintance with the true cha- 



