1867.] MACFARLANE— GEOLOGY OF LAKE SUPERIOR. 179 



sionally bluish tinted. The specific gravity of the rock is 2-750 

 to 2-703. Large-grained granite is of very frequent occurrence 

 on Montreal River and on the coast betwixt it and Point-aux- 

 Mines. It consists principally of orthoclase, in pieces from one 

 to several inches in diameter, a comparatively small quantity of 

 quartz, and a .still smaller proportion of white mica. The 

 promontory of Gros Cap, at the entrance of the Lake from River 

 St. Mary's, is composed of coarse-grained and characteristic 

 syenite. In some places its hornblende is soft, seems decomposed, 

 and is accompanied by epidote. The rock is seldom free from 

 quartz, and some of it contains so much as to be justly termed 

 syenitic granite. A chloritic granite appears to occur at a few 

 points on the north side of Bachewalmung Bay, and a small- 

 grained granite, consisting exclusively of felspar and quartz, 

 occurs in large masses at the north-western extremity of the same 

 Bay. It has not the structure of granulite, and might be properly 

 named aplite or granitelle. 



These rocks are all unequivocally granular, without a trace of 

 parallel structure. They far exceed in frequency and extent those 

 which possess a thoroughly gneissic character ; indeed, character- 

 istic gneiss was only observed at Goulais Falls and at Point-aux- 

 Mines. The rock of the latter locality varied from the closely 

 foliated, resembling mica schist, to that of a granitic character. 

 Granitic gneiss is found on the north shore of Bachewalmung Bay, 

 between Chippewa River and Bachewalmung Village, on the road 

 between the latter and the Bachewalmung Iron Mine, in the 

 neighbourhood of the Begley Copper mine, and at other points on 

 the north shore of Bachewalmung Bay. 



Almost equal in frequency to these thoroughly granitic and 

 gneissic rocks, there are found certain aggregates of rocks which 

 present different lithological aspects almost at every step, and 

 which can only be generally described as brecciated and intrusive 

 gneissic, granitic, or syenitic rocks. There is, however, to be 

 detected a certain uniformity in the manner of their association 

 with each other, which is of the greatest interest, and several 

 instances of which it is now proposed to refer to. On the north 

 shore of the Lake, about twenty-five miles west of Michipicoten 

 Harbour, one of these rock-aggregates may be observed. Here 

 fragments of a dark schistose rock, consisting of felspar and horn- 

 blende (the latter largely preponderating), are enclosed in a 

 coarse-grained syenitic granite, and both are cut by veins of 



