682 REPORT—1885. 
8. Professor Bonney has kindly undertaken to report on the rock and 
mineral specimens collected by Mr. Johnston, and lhiy report is presented 
herewith, and will be read in the Geological Section. 
9. Mr. H. H. Johnston has in preparation a volume containing a 
narrative of his expedition and a summary of the results arrived at, 
which will shortly be ready for issue. 
10. The sum of 25]. granted to the Committee at the Montreal 
meeting has been returned to the Treasurer. 
- APPENDIX. 
Report on the Rocks collected-by H. H. Johnston, Esq., from the wpper part 
of the Kilima-rjaro masstf. By Professor T. G. Bonney, D.Sc., F.BRS., 
Pres. G.S. 
The collection consists of forty rock and six mineral specimens—most 
of them rather small pieces—which in several cases have evidently not 
been broken from rocks in situ, but have been lying about on the ground 
as loose fragments. 
(1) Stream Valley, Kilima-njaro, 13,000 feet (16 fragments).—These 
- are rolled pebbles or fragments, more or less waterworn, varying in 
diameter from about three-quarters of an inch to one and a-half inch. 
They consist of a black glassy rock, of a very dark grey subvitreous rock, 
or an extremely compact lava (all obviously not very different from glassy 
basalts), together with five specimens of more or less scoriaceous rock, 
the last named being more waterworn than the other. These are a dark 
compact rock, containing crystals (sometimes quite an inch long) of a 
glassy felspar in rather tabular crystals, which is probably identical with 
one to be presently described. Of the former group I aye selected three 
for microscopic examination as being fairly representative of the series. 
(a) Fragment (somewhat rounded) of black glass of slightly resinous 
lustre, with faint indications of a fluidal structure. Examined micro- 
scopically, it appears as a banded brown glass, varying in colour from a 
rather pale to a warm brown tint. Both, but especially the latter, are 
streaked with elongated trichites of dark brown to black colour, and the 
darkest band is beautifully ‘marbled’ by darker streaks and filamentous 
trichites. Scattered about are acicular microliths; some of the smaller 
and thinner are probably felspar, but certain of the larger show good 
hexagonal sections, and may be safely identified as apatite. Three or 
four rounded grains, associated twice with apatite and once with magne- 
tite (?) also occur. They are either olivine or augite—I think the latter ; 
neither cleavage nor external form is sufficiently definite to enable me to 
speak with certainty. I regard them as the remnants of crystals, of 
which the external angular portion has been melted away. ‘The rock 
may be classed with the angite-andesite glasses, and belongs to the more 
basic side of the group. 
Az 
(b) A similar rock, but with a rather duller lustre. Examined with ~ 
the microscope under a low power, it seems to be a rather opaque-looking 
darkened grey glass. With high powers, there appears to be a base of 
clear glass from which the magnetite has separated in minute granules 
and ‘dusty’ patches and a number of very minute belonitic crystals, — 
probably felspar, have formed. There are slight indications of fiuidal — 
structure. In the slide is a perfectly round grain of hornblende, a frag- 
ment or two of felspar, a few small crystals of apatite (?), and two bits 
, 
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