NORTHWEST 



OF LAKE SUPERIOR. 



355 



tant point, but too far removed from the focus of volcanic action to have been 

 affected by the causes which produced so great a change in the slate-beds in near 

 proximity to the trap-dikes, and where they alternate with basaltic beds. 



Some of the beds of No. 348, as before stated, are amygdaloidal. They contain 

 large nodules, from one to three inches in diameter, formed by concentric layers of 

 a siliceous material, and are filled with beautiful crystals of laumonite and calcareous 

 spar. These nodules resemble, in all respects, except size, many of those occurring 

 in the altered clay slates of Encampment Island River. The rock containing them 

 on this stream, however, has been so changed by igneous action as to bear no resem- 

 blance, in general appearance, to that of Encampment Island River. 



Below the mouth of Kinewabik River, the section along the lake-shore exhibits 

 beds of shale, like those already described, with overlying trap-beds, until the first 

 point is reached, where there is a heavy dike of greenstone (No. 613), which cuts 

 through all the sedimentary beds, and near the contact alters the schistose rocks to 

 No. 614. 



The overlying and sedimentary rocks then continue along shore, and around the 

 point to the next bay. At the point, however, a north-30°-east dike shows itself, 

 and assumes a somewhat columnar form as the turn is made into Encampment 

 Island Bay. In this bay, the overlying trap (No. 333) is about one hundred and 

 twenty feet in thickness, and rests upon thirty-five feet of metamorphosed shales, 

 with beds of a very compact rock intervening, as shown in the annexed section. 



a. Trap. 



b. Compact rook, trnppous-looking. 



c. Metamorphosed shales. 



The bottom of this bay presents a shingle beach, with a heavy deposit of red clay 

 and marl on the lower side, as far as the point opposite the island. For the last 

 three miles of the shore, the dip of the bedded rocks is very irregular, varying from 

 northwest to southeast. 



7. Encampment Island River. — This river was explored to the distance of four 

 miles, in a direct line from the Lake. At its mouth there is a deposit of drift 

 and red marl, which continues for about a quarter of a mile up stream, when 

 amygdaloid appears in the river-bed, dipping southwest 7°. This rock continues 

 about two hundred yards, when a very hard, compact, fine-grained, siliceo-argilla- 



