92 LAKE SUPERIOR. 



July Zlth. We had intended to cross to Isle Royale, which lay 

 like a blue cloud along the horizon, twelve or fourteen miles off, and 

 vanishing into the distance eastward. Having got outside of the 

 chain of islands, however, we found the wind so strong as to render 

 the traverse dangerous, and we accordingly landed on one of the 

 Victoria Islands, west of Spar Island, to wait for some change of 

 weather. 



The beach where we landed was a mere niche cut into the side of 

 the cliff, which rose steeply on all sides, thickly wooded. The 

 ground everywhere covered with moss. Among the trees on the 

 bank was the skeleton of a lodge, and a birch canoe apparently in 

 good condition. Some playthings of the Indian children were lying 

 about, among others a little boat scooped out of a chip of wood, with 

 mast and bowsprit, precisely such as the boys make with us, and not 

 at all resembling the Indian canoes. The frequency of these traces 

 of Indian encampments, with the small number of Indians living on 

 this part of the lake, shows their restless, wandering disposition. 



While we were detained here, the Professor made some remarks 

 about the theory of the formation of mineral veins by infiltration. 

 This theory he considered untenable, since there is an evident con- 

 nection between this phenomenon and some action of the walls of the 

 fissures in which veins are found : 



' Thus at the vein we examined this morning at Prince's Location, we 

 found each wall of the fissures covered with quartz crystals whose axes 

 were perpendicular to the walls : those inside were crystals of calc-spar dis- 

 posed in the same way. An electro-magnetic action, (which has been pro- 

 posed by some geologists,) would fully account for this arrangement. If 

 we suppose an electro-magnetic current passing through the fissure, this may 

 have brought together similar particles scattered through the rock, and dis- 

 posed them in the manner we see. In order to settle this point, however, 

 it would be necessary to ascertain whether there is any constant relation in 

 the arrangement of substances found in veins of different localities : 

 whether the minerals always follow each other in the same succession If 

 this be the case, it will give great probability to the supposition of an electro- 

 magnetic current, over that of any merely mechanical agency like infiltration. 

 Such an examination might probably also distinguish the cases where veins 

 are formed by sublimation or deposition from vapors or gases from below. 



