NARRATIVE. 93 



'Where the vein is composed of minerals not found in the surrounding rock, 

 the probability would be in favor of sublimation : where the minerals occur, 

 though in small quantities, in the rock, there the effect may have been pro- 

 duced by electro-magnetism. There has been as yet no sufficient investiga- 

 tion of this point. 



" It may be remarked here that even where the vein is composed of 

 hydrates, in whose composition water occurs, it is not necessary to suppose 

 them deposited by infiltration, since it has been proved that hydrates may 

 be formed by sublimation." 



We remained here until half past three o'clock P.M., when, the 

 weather continuing unfavorable, and even threatening a storm, we 

 decided to give up our visit to Isle Royale, and to turn our faces 

 homewards. 



The distance of this, our westernmost point, from the Sault, was 

 about four hundred and forty miles by the way we came ; as we 

 returned, rather more. 



The wind was fresh from the southward, and when we got outside 

 of the islands there was so much sea that the other canoe, although 

 within a short distance of us, often disappeared, sail and all. It was 

 rather a long swell for the lake, however, and we did not experience 

 any dilficultj from it, as we were nearly before the wind. We en- 

 camped on an island to the southward of the Pate, in a deep bay 

 with steep sides, overshadowed by trees of unusual size. 



July 2Sth. — Started before sunrise. Weather calm and pleasant. 

 We passed under the south-east side of Pie Island, a vertical cUff 

 several hundred feet in height, presenting much the same appearance 

 as Thunder Cape, viz : basaltic columns, across which may be traced 

 the marks of an horizontal stratification. These columns in some 

 places have fallen out, leaving hollows, hke flues, in the side of the 

 chff. In other places single columns stand out alone, like chimneys ; 

 ui others, again, huge flat tables of rock have scaled off from the 

 face of the wall, and stand parallel and a Uttle separated from it. 

 The metamorphosed strata in one place were unconformable, exhibii>- 

 ing a sudden fault. 



In the course of the forenoon several trout were caught, and the 

 diversity of color led to some discussion. The men said there j^^ere 

 three varieties, all of the same species: 1. the trout of the open 



