40 J GEOLOGICAL SURVEY OP CANADA. 



On the north bide the rock is a dark, granitic, orthoclase hornblende- 

 gneiss, associated with thick masses of dark-green hornblende-rock, 

 containing grains of magnetite; the source of the colors of iron-sand 

 frequently seen along the river shore. 



At the chute are two dark-green trap dykes, weathering reddish- 

 brown, which run S. 6G Q W. and S. 47° W., being respectively four 

 feet and nine inches wide. On the north side, one-quarter of a mile 

 below the chute, is a similar dyke, eighteen feet wide, running S. 15° W. 



Three-quarters of a mile above the chute is an exposure of hoi-n- 

 blendic schistose gneiss, composed of alternate lamina; of blackish, 

 green hornblende and yellow weathering, grey felspar with patches of 

 reddish orthoclase. In some parts the rock is a dark, fine-graiued, 

 hornblendic gneiss, with" large porphyritic crystals of whitish felspar, 

 the largest crystals being one and a-half inches long by one-half inch 

 broad, with their longer axis always parallel to the plane of stratifica- 

 tion. Strike S. 75° W. 



Five miles beyond the last, on the south bank, is a fine-grained, 

 bluish grey gneiss made up of dark hornblende and bluish felspar, with 

 little or no quartz, containing enclosures of dark hornblendic segrega- 

 tions. Strike S. 60° W. 



One mile and a-quarter above the last there are exposures of fine- 

 grained dark-grey hornblendic gneiss, weathering greyish yellow, 

 containing porphyritic crystals of white felspar, and traversed by veins 

 of pink orthoclase also having hornblende segregations. 



Three miles beyond was seen similar hornblende gneiss, with massive 

 hornblende rocks like those at the chute, also light pink highly fels- 

 pathic gneiss containing much less hornblende and more quartz than 

 the darker grey rock. Strike N. 85° W. 



One mile farther up is more of the dark grey hornblendic gneiss and 

 black massive hornblende rock. 



Three miles and a-quarter beyond the last are exposures of the por- 

 phyritic gneiss. Strike B. by W. 



At the small rapid on the bend below the portage is a coarse red and 

 grey gneiss, composed chiefly of red and grey orthoclase, crystals of 

 which are perfectly developed, along with slightly altered dark-green 

 hornblende and some mica and quartz. Strike S. 77° W. 



Portage Route between Big and Bishop Roggan Rivers. 



„. Leaving Big Eiver at the portage, the route passes overland, on 



Bishop Roggan a general course of N. 40° E. by a number of portages connecting small 



lakes, draining into Big Eiver through a large lake on a river 



which flows into James Bay a tew miles north of the mouth of Big 



