236 Reports and Proceedings— 
he terms granitite-gneiss ; the basic series, which consists of rocks 
containing little quartz and much plagioclase felspar, tonalite-gneiss. 
The unfoliated specimens comprise granite, gabbro or noriie, 
pyroxene-granulite, and pyroxenite. 
The majority of the granites are of the granitite-type—t.e. they 
are granites with one mica; but granites with two micas are also 
represented. 
The remainder of the rocks are of a basic type. They are in- 
teresting, in the first place, on account of the striking combinations 
of fresh and beautiful minerals they present, as for example :— 
plagioclase, hypersthene, olivine, brown hornblende and green spinel, 
in an olivine-norite; or, plagioclase, green pyroxene (omphacite or 
diallage), hypersthene, hornblende, garnet and iron-ore, in pyroxene- 
granulite; or, again, diallage and hypersthene in pyromentte. 
But of greater interest is the fact that these basic types, which 
are so well known in other territories of old crystalline rocks— 
Saxony, Brittany, Scandinavia, Scotland, the Hudson River, etc.— 
constitute in Madagascar, as they do at Kilima-njaro on the adjacent 
mainland, a large part of the ancient platform on the submerged 
portions of which the sedimentary rocks have accumulated, and 
through which the volcanic lavas were erupted. 
il. The Volcanic Rocks.—In composition these are acid, inter- 
mediate and basic, mainly the latter. The acid and intermediate 
types are described are sanidine-trachyte and hornblende-augite-andesite. 
The basic rocks consist of various types of basalt. They vary with 
respect to the presence or absence of corroded quartz-grains, 
olivine, porphyritic hornblende, and biotite. In one interesting type 
the hornblende appears in small idiomorphic crystals as a constituent 
of the ground-mass. A felspar-free variety, or magma-basalt, is also 
represented. This rock contains only a small quantity of olivine, 
and is therefore intermediate between Rosenbusch’s Limburgite and 
Dolter’s augitite. 
IIJ.—March 20, 1889.—W. T. Blanford, LL.D., F.R.S., President, 
in the Chair.—The following communications were read : 
1. “Supplementary Note to a Paper on the Rocks of the Atlantic 
Coast of Canada.” By Sir J. W. Dawson, K.C.M.G., F.B.S., 
¥.G.8. 
In a paper in the “Journal” for November, 1888, the author 
referred to the Olenellus-fauna as characterizing the Middle Cam- 
brian. The fauna, he has no doubt, from the recently published 
observations of Walcott and Matthew, should be regarded as charac- 
teristic of the Upper Member of the Lower Cambrian. From this 
arises a new view of the physical geography of the period, namely, 
that the Lower Cambrian was, in America, a period of continental 
depression, and the Middle Cambrian a period of continental elevation, 
leading to the important conclusion that a time of elevation inter- 
vened between the Huronian and the early Cambrian, which may 
represent the apparent gap between these systems in LHastern 
America. He thinks that this new view deserves a special mention 
