NORTHWEST OF LAKE SUPERIOR. 



351 



joints are lined with heulandite. The shore of the large bay is composed of red 

 clay and marl beds. At the point of the large bay, into the east side of which 

 Carp River empties, No. 589 shows itself. The dike is large, and is cut directly 

 across by the lake-shore, which exposes, lower down in the bay, its central portion, 

 which rises rapidly from the shore, and forms a high ridge. About two-thirds the 

 distance down the bay, No. 589 is traversed by a dike of No. 608, bearing north 

 15° west, and accompanied by a vein containing calcareous spar and zeolites. 



In the bay above Knife Island, No. 588 forms tabular masses along shore, and 

 continues on as far as the point opposite Knife Island. It appears to be bedded, 

 and is traversed by numerous veins, which cross it at right angles to the line of 

 bearing. In the centre of this bay is a small projecting point, made by a heavy 

 dike of No. 607, bearing north 5° east. Further east, the bedded rocks dip to the 

 southwest, but at Knife Island Point the dip is east. This point is from ten to 

 twelve feet high, and is composed of No. 588, which also forms the island. 



- 5. Knife River. — This is the Mokoman Sibi of the Chippewas, and is one of the 

 largest streams between Two Island River and Fond du Lac Superieure. 



On the lake-shore, immediately below the mouth of this river, is an exposure of 

 bedded rocks, very nearly resembling the ordinary metamorphosed sandstones of 

 this region, but which, in consequence of some differences in their composition 

 from that of common sandstone, as well as some differences of association, I have 

 been led to believe were contemporaneous with the eruption of the dikes and bedded 

 traps with which they are associated, and have therefore called them volcanic grits. 

 The trap-dikes which have been erupted through these grits, produce quite as great 

 a degree of metamorphosis in them as they do in the sandstones and other sedimen- 

 tary rocks, and the changes thus produced add no little to the perplexity of the 

 geology of the district in which they prevail, especially where continuity of the 

 strata has been subsequently broken up by faults and upheavals. 



Four beds of grit are exposed at the point designated (Nos. 325, 322, 323, 324), 

 in the order in which they are named, No. 325 being the top rock. These beds 

 overlie, a short distance up the river, a bed of basaltic rock (No. 354), which is 

 seen in the banks for the distance of half a mile. It appears to be regularly bedded, 

 and dips east by south at an angle of 11°. The next rock which comes up is a 

 metamorphosed slate (No. 355), which, at some places, resembles the hornblendic 

 slates of Pigeon River, but at other points is slightly altered, and shows with the 

 greatest clearness the laminae of deposition and the cleavage-joints. At other 

 points again, it is changed to a hard, dark brownish-coloured rock, with occasional 

 cells, containing Thalite,* and nodules of chalcedony. These rocks (Nos. 355, 356, 

 357, 358) probably alternate at this locality, as they were found to do at other 

 places, as on Pigeon River, for example ; but no positive evidence of such alterna- 

 tion was seen on this stream, the rocky banks of which are low, and the section not 

 illustrated by exposures on the sides of the hills. 



At the distance of a mile and a half from the Lake, the river is crossed by a dike 



* The new mineral described by Dr. Owen. 



