SOURCE OP ST. Peter's river. 157 



carved upon the hill over which it passes. This figure is 

 nearly obliterated, but from the description probably re- 

 sembles representations of otters, &c. near Lake Travers ; 

 it is supposed to have been executed by a party of Sioux, 

 who had advanced thus far on a warlike excui'sion ; this 

 shows how far they sometimes carry their inroads into 

 their enemies' territory. 



On descending Dog portage we found mica-slate in situ 

 on the east side of the hill, and this we observed still more 

 distinctly at the next portage, where the sharp lamina of 

 the slate, resembling the blades of cutting instruments, 

 have caused it to receive the name of Knife or Devil port- 

 age. Although it was late when our party reached this 

 place, yet we had occasion to observe a junction of the slaty 

 and greenstone rocks. The greenstone underlays the slate, 

 whose strata are directed north fifty degrees west, and incline 

 to the north-east about seventy degrees. There does not ap- 

 pear to be a passage from the one into the other ; but a ten- 

 dency to the formation of both rocks probably existed at 

 one time, whence the mica-slate was deposited immediately 

 after the greenstone, no interval of time occurring between 

 the formation of the two, as appears from the fact that we 

 find patches of the latter enclosed in the inferior strata of the 

 former, and also some portions of mica-slate in the superior 

 part of the greenstone mass ; as the latter is not stratified, we 

 could not determine whether the slate lay in parallel su- 

 perposition, though we have reason to believe that it does. 

 We observed that the masses of greenstone enclosed in the 

 mica-slate lay in a direction parallel to the stratification. 



The descent on the east side of the height of land is very 

 rapid, as can easily be observed in passing the portages. 

 On the 12th of September, we travelled thirty -five miles, 

 and the difTerence of level which we observed in the wa- 



