Studies on some Japanese Rocks. 227 



basal sections, first pointed out by Mr. Whitman Cross, and which is 

 characteristic of triclinic and not of monoclinic crystals. A careful 

 examination of the question has led the author to conclude that the 

 mineral which has lately been regarded as a rhombic pyroxene 

 (probably hypersthene) is really only ordinary augite cut parallel to 

 the optic axis. He does not regard the property of pleochroism as 

 distinctive of hypersthene, while the absence of a brachypiuacoidal 

 cleavage and the presence of 10 per cent, of lime in the mineral 

 forbids our referring it to that species. 



The other abundant minerals in these augite-andesites are mag- 

 netite, which is always present, and quartz, which occurs in some of 

 them, both as a primary and a secondary constituent. Hornblende 

 is very rare in these rocks, and when present the peripheral portions 

 of the crystals are seen to be converted into augite, probably by the 

 action of the caustic magma upon them. Enstatite is rare in these 

 rocks, but apatite is always found in them, while tridymite occurs 

 not unfrequently. 



The author described a number of structural variations in the 

 augite-andesite from different localities. Among the most inter- 

 esting is a variety containing as much as 69 per cent, of silica. 



Among the less abundant rocks are the enstatite-andesite, the 

 quartz-augite-andesite, and the hornblende-andesites. The plagio- 

 clase-basalts of Japan can only be distinguished from the augite- 

 andesites by the presence in them of olivine. Magma-basalts are 

 rare, most of the varieties being of the dolerite type ; but under the 

 name of " basalt-lavas" the author describes varieties with a glassy 

 base. 



In an Appendix some account is given of a number of pre-Ter- 

 tiary rocks, including granite, one variety of which contains the new 

 mineral, reinite, of Pritsch (the tetragonal form of the ferrous- 

 tungstate), quartz-mica- diorite, diorite-porphyry, and diabase. 



April 23.— Prof. T. G. Bonney, D.Sc, F.E.S., President, 

 in the Chair. 



The following communications were read : — 



1. " On the Geology of the Country traversed by the Canada 

 Pacific Eailway, from Lake Superior to the Eocky Mountains." By 

 Principal J. W. Dawson, C.M.G., P.E.S., P.G.S. 



This paper recorded observations made by the author with refer- 

 ence to the geology of the north-west territories of Canada, in an ex- 

 cursion in the summer of 1883, along the line of the Canada Pacific 

 Eailway as far as Calgary, at the eastern base of the Eocky Moun- 

 tains. 



After referring to the labours of the Canadian Geological Survey, 

 and more especially of Dr. G. M. Dawson, P.G.S., in this region, 

 the author proceeded to notice the Laurentian, Huronian, and other 

 Pre- Silurian rocks of the west of Lake Superior and the country 

 between that lake and the Eed Eiver. Good exposures of many of 



