14 GENERAL GEOLOGY 



toid rock, which was seen to widen out to the eastward, 

 on the point of the cove, into a considerable mass. This 

 proved to be a biotite-tonalite (i), rather coarse and grani- 

 toid in texture and rich in titanite, a very characteristic 

 rock for this whole region. 



About 200 miles north of Beaver Cove we touched at a 

 waterfall on the eastern shore of Princess Royal Island, 

 near the northern end of Fraser Reach, and found the same 

 uniform-textured biotite-tonalite, containing some horn- 

 blende and a notable amount of honey-yellow titanite in 

 sharp crystals. This rock apparently constitutes both 

 shores of the channel the whole length of Fraser Reach 



FIG. I. DIKES, LOWE INLET, B. C. 



and the upper two-thirds at least of Graham Reach, a dis- 

 tance of about 40 miles. It was found again on the main- 

 land in Lowe Inlet, a branch of Grenville Channel, 50 

 miles farther north, where we next landed. The tonalite 

 (7 and 10) is here somewhat coarser and less homogene- 

 ous. Its principal feldspar is a basic oligoclase, beauti- 

 fully zoned, and twinned on the albite and Carlsbad laws. 

 There is very little orthoclase or quartz. Biotite is abun- 

 dant, and some sharply idiomorphic green hornblende is 

 present. Apatite, zircon, titanite and epidote (apparently 

 original) were observed as accessories. The rock is here 

 extremely fresh, and is lighter colored than at points pre- 

 viously visited. 



