SOURCE OP ST. Peter's river. 195 



parts to contain much quartz and iron pyrites. This rock 

 rises higher than the coast usually does ; it forms a vertical 

 cliff, which appears to be undergoing a very rapid destruc- 

 tion ; but the fragments, instead of collecting at the base and 

 forming an inclined plane, are washed away, so that the 

 waters of the lake come up to this vertical bank, which 

 rises like a wall, enclosing the lake. Pyrites appears to 

 abound throughout the mass. It is probable that, at 

 the junction of this rock with the sienite, the river has 

 forced its way into the lake, and that the wide bay of Mi- 

 chipicotton has been opened, for on the east side we again 

 saw the sienitic rocks predominating. At the bay in which 

 we stopped, five miles east of the trading house, we ob- 

 served the sienite to be intermixed with other rocks, one 

 of which contains a greater abundance of hornblende, and 

 forms a real greenstone ; another portion is mixed with 

 talc, and a third portion contains hard nodules of quailz, 

 which would at first convey the idea of a conglomerate, but 

 which, being examined more closely, appear to present no 

 characters but such as are entirely compatible with a pri- 

 mitive and highly crystalline formation ; these nodules of 

 quartz are connected by a talcose cement. All these varie- 

 ties are found together, and belong to the same general 

 mass, of which they form but local or partial features. They 

 are all penetrated by iron pyrites, in great abundance, 

 which in some points were evidently mixed with copper 

 pyrites ; all these were examined with care, in hopes of 

 meeting with the native copper, and with other ores of the 

 same metal besides the pyrites ; our search was, however, 

 unsuccessful. The great interest which generally prevails 

 on the subject of the copper mines of Lake Superior, as 

 they are called, will perhaps justify us in offering, on this 

 subject, a few observations, which we hazard with some 



