NORTHWEST OF LAKE SUPERIOR. 



357 



quarter of a mile above this fall, the greenstone, in the bearing of which the stream 

 rims for that distance, disappears under a heavy deposit of clay, marl, and drift ; 

 and five hundred yards further up, the conglomerate shows itself again for the dis- 

 tance of three hundred yards, where it is overlaid by metamorphosed sandstone (No. 

 345), which forms the bed of the river for half a mile, and then dips beneath the 

 clay and marl beds. 



At the point where the exploration of this river ceased, the country is gently 

 undulating, and timbered with pine, birch, hemlock, spruce, mountain ash, small 

 maple, and cedar. 



Encampment Island appears to be a fragment of the great greenstone dike (No. 

 613), seen at various points on the Lake shore, below the mouth of Kinewabik 

 River. At the easterly end of the island, it is cut across by a north-and-south dike 

 (No. 015), which appears at the opposite point on the mainland, where it has pro- 

 duced great disturbance in the bedded rocks, as shown in the following figure. 



b a b c b 



a. Greenstone. J, b, b. Metamorphosed beds. c. Clay and marl. 



The rocks clip east and west, and on the east side the dip amounts to 41°. In 

 the same bay, however, two hundred yards below the dike, the dip is to the west, 

 at an angle of 9°. This continues for about three hundred yards, when the dip 

 gradually changes until it is to the east. The dike producing the disturbances in 

 the bedded rocks is not visible for some distance on the shore, but in the second 

 bay below the island it is again seen (No. 333) above the water-level, overlaid by 

 about sixty feet of metamorphosed rocks. In the bottom of this bay the north-45°- 

 east dike (No. 613) contains immense fragments of a massive felspar rock* (No. 

 616). At the projecting point below this, there are some beds of trap between 

 those of the metamorphosed rocks, which appear to be lateral injections from the 

 dike. At one point the section consists, as here shown, in descending order, of, 



a. Trap-beds. 



b. Shaly-beds. 



c c. Red clay and marl. 



a a. Trap-beds. 



1st, a bed of red clay and marl, overlying a bed of basaltic rock ; 2d, thinly lami- 

 nated siliceous shale (No. 316), very much altered in some places, and nearly un- 

 altered in others. It contains organic impressions like those found on Passabika 

 River, and also large waterworn fragments of other rocks. It weathers into caverns. 

 3d. A bed of basaltic rock, which has altered the shales near its contact with them 

 into a hard, compact rock, with a hackly fracture, and a semi-columnar structure. 



* An analysis of this rock is given elsewhere. 



