384 DESCRIPTION OF THE COUNTRY BORDERING 
A section of the rocks immediately below the mouth of this river, is exhibited in 
the annexed cut. The underlying rock is a shaly amygdaloid; above that, a bed 
e. Shaly amygdaloid. 
ad. Volcanic grit. 
ec. Volcanic ¢ eit, with shales. 
b. Breccia. 
a. Shaly amygdaloid. 
of amygdaloidal breccia, and over that, a bed of volcanic grit (No. 146). These 
beds are all somewhat disturbed, and traversed by veins of calcite, in one of which 
I found traces of green carbonate of copper. In proceeding from the Lake, the 
metamorphosed shales become much thickened, and are associated with beds of 
altered grit, and occasional exposures of a corrugated bed. They form the shore of 
the first two bays, overlaid by a bed of trap. In the third one, there are altera- 
tions of shale and thin beds of trap (No. 133), which are greatly disturbed, and dip 
south and southwest. At the point of this bay, is a beautiful exhibition of basaltic 
columns projecting into the Lake, of which the following sketch by Major Owen 
will give a much better idea than a written description. The exposure is about 
BASALTIC COLUMNS, LAKE SUPERIOR. 
twenty feet in height, and the columns rest on beds of metamorphosed grit, over- 
lying decomposing amygdaloidal shales; showing conclusively, I think, that the 
basalt here is an overflow, and does not occupy the original site of eruption. 
Beyond this point the exposures are low, and consist of metamorphosed shale and 
sand-rock, until the middle of the bay is reached, where they are cut through by a 
