1867.] MACFARLANE — GEOLOGY OF LAKE SUPERIOR. 191 



Harbour and Island. In the neighbourhood of, and on the road to, 

 the Bachewahnung Iron Mine, they are also plentiful. Not unfre- 

 quently the pyroxene in them assumes the appearance of diallage. 



AugiUporphyry. — The porphyritic diabase above referred to is 

 a small-grained diabase, in which are disseminated crystals of 

 pyroxene, about three-eighths of an inch in diameter. The specific 

 gravity of the rock is 2-906. Its fine powder has a light 

 greenish grey colour, which changes on ignition to dark brown, 

 2.01 per cent, of loss being at the same time sustained. Hydro- 

 chloric acid dissolves from it 2348 per cent, of bases. 



Calcareous Diabase. — The amygdaloidal diabase above men- 

 tioned is the same rock as is termed by Naumann Kalkdiabase. 

 It is a fine-grained diabase, somewhat schistose, in which oval- 

 shaped concretions of granular calcspar occur. The latter are 

 not, however, always sharply separated from the mass of rock, 

 which is slightly calcareous. The amygdules, if such they can 

 be called, have their longer axis invariably parallel with each 

 other, and with the schistose structure of the rock. 



Diabase Schist. — This rock occurs much more frequently than 

 either of those just described. It is, indeed, difficult to find a 

 diabase among these Huronian rocks which does not exhibit a 

 tendency to parallel structure, or which does not graduate into 

 diabase schist. But the latter rock occupies- considerable areas 

 by itself, not only on Goulais River, but also on that part of the 

 north shore referred to in this paper. The higher hills to the 

 north-east of Goulais Bay consist, to a large extent, of this rock. 

 Apart from its schistose structure, it possesses the characters of 

 diabase. For example, a specimen of the rock from the north 

 shore has a specific gravity of 2-985. Its powder, which is light 

 grey, changes on ignition to light brown, losing 1-43 per cent, of 

 its weight. On digestion with hydrochloric acid, it loses 14-21 

 per cent, of bases; and with sulphuric acid, 16-12 per cent. It 

 is fusible before the blow-pipe. Many of these schists are 

 pyritiferous and calcareous, and these graduate frequently into 

 greenstone slate. 



Greenstone and Greenstone Slate. — The rocks above mentioned, 

 being small-grained, are recognizable without much difficulty ; 

 but, besides these, and occupying much more extensive areas, 

 there occurs finely granular and schistose rocks, many of them 

 doubtless of similar composition to the above mentioned diabase 

 and diabase schist. Where the transition is traceable from the 



