250 On the Geography and Geology 



much ; and more or less hornblende, sometimes very little. About 

 the Written Rocks the last ingredient is rather plentiful. There is 

 also a little copper-coloured mica ; and a few small garnets. The 

 structure is large granular. There is no difference between this 

 rock and certain forms of the granite west of Michipicoton Crags. 

 Veins of white quartz are common here, usually of moderate size ; 

 but half a mile east from the Black River a vein occurs from three 

 to five yards broad, containing films and masses of granular 

 epidote, on which is deposited purple fluor spar. Trappose veins 

 in every respect similar to those around Otter's Head are occa- 

 sionally met with in this granite, going W., W.N.W., W.S.W., S^c. 



The craggy line of shore, ending on the west in Cape Verd, is 

 of the greenstone so often met with ; but the interior, a mile or so 

 in the rear, still consists of the red granite of the Written Rocks ; 

 and so continues along the main for a great distance into Nipigon 

 Bay. This is, therefore, the northern portion of a greenstone 

 deposit covered by the lake. At the east end of this line of cliffs 

 and shelves it is the usual pale greenstone ; but in displaced and 

 weathered masses buried under a profuse vegetation. It however 

 darkens gradually, and at the west end is very black, and contains 

 knots and coatings of white calcspar, which drop out, leaving the 

 rock vesicular. I landed near, and found the several hues of green- 

 stones intermixed in a curious manner ; but which I had not lei- 

 sure to unravel. There are here also balls of concentric laminse, 

 the same (except in being darker) as in the greenstone immediately 

 east of the Black River. Large and extremely well characterized 

 trappose veins traverse the greenstone. 



The north shore of Lake Superior from Point Marmoaze to Cape 

 Verd, has presented a series of rock masses of great extent, suc- 

 ceeding each other abruptly and without admixture, but connected 

 strongly by the similarity in composition of its several alternating 

 members, respectively, and by tlie presence of trappose veins in 

 all ; and of calcspar, a mineral unusual in some at least. Fluor 

 occurs in the granite, sienite, amygdaloid, and porphyry. We 

 now enter among rocks still more closely allied ; but such is the 

 intricacy of the region in which they are placed, both as to its 



