1867.] 



MAC FAR LANE— GEOLOGY OF LAKE SUPERIOR. 



181 



finer-grained granite, of a much lighter colour than the gneiss, 

 and comparatively poor in the black mica. The specific gravity 

 of the gneiss is 2-667, and that of the granite, 2-6-18. Veins of 

 large-grained granite, containing very little mica, traverse both 

 of the rocks just mentioned. The appearance of these rocks 

 is shewn in Figure 2. At the falls of the Chippewa or 



Fig. 2. 





m 



mm^ ■ ^■■^&if ■ ■ ■ 



mmMfn 



■■■-■•'iMSm'--- 



a. Granitic gneiss. | b. Fine-grained granite. | c, Large-grained granite. 



Harmony River, which empties into Bachewahnung Bay, the 

 predominating rock is highly granitic gneiss, consisting of reddish 

 orthoclase, quartz and dark-green mica. It is rather small- 

 grained, and, when observed in mass, shows sometimes a schistose 

 appearance, the direction of which ranges from N. 10° W. to N. 

 57° E. Occasionally, in the more micaceous portions, broad 

 felspathic bands occur, with selvages rich in mica, forming the 

 nearest approach to gneiss. The direction of these bands is 

 altogether irregular. This is also the case with veins of large- 

 grained granite which intersect the rock just described. This 



