242 On the Geography and Geology 



resembling sienite ; the granite being at first in ramifications ; but 

 it augments in quantity gradually westwards, until the greenstone 

 of Michipicoton completely disappears. 



This granite predominates from the west end of the crags to 

 within 2 miles of the River Peek, a distance of 73 miles, inter- 

 spersed with greenstone similar to that just noticed, and traversed 

 in all directions by veins of trap. This rock, which some may be 

 tempted to name a sienite from its abundance in horht)lende, dis- 

 seminated in small crystals, I consider as granite, from the actual, 

 though scanty presence of black mica, the universal and plentiful 

 occurrence of white or limpid quartz, and from the very capri- 

 cious proportions of hornblende ; which I have strong reason to 

 believe is sometimes replaced by chlorite, as I have met with large 

 angular blocks of white granite, containing this substance dissemi- 

 nated, near the west end of Michipicoton Crags. Near the 

 Crags, and for a iew miles westwards, this granite, differing from 

 the granular, or small porphyritic kind of Huggewong Bay only in 

 its (usually) increased quantity of hornblende, and in the colour 

 of its feldspar (which is often very red), mingles with a greenstone, 

 which has veins of epidote, and is rarely rendered porphyritic by 

 crystals of feldspar. It is, perhaps, entitled to the name of trap, 

 judging from its small crystalline structure, massiveness, and dark 

 colours. 



The line of junction of these rocks is extremely irregular, and 

 neither rock is changed at the point of union. I have observed a 

 string of epidote pass from the greenstone to the granite, unbroken. 

 The latter seems to intrude from below on the former, in whole 

 bluffs, or in large knots, and wandering veins. About two miles 

 west of the Crags, the greenstone is distinctly seen to rest on an 

 inclined and flattened mass of granite, and to receive from it large 

 veins. These intermixtures vary much in their extent ; each rock 

 occupying a few yards, or even a mile of the examinable ground 

 between the water and the woods. It is to be remembered that 

 from the inaccessible nature of the country, and the magnitude of 

 the depositions, we seldom see rocks superimposed on each other, 

 on the north side of Lake Superior ; and are thus deprived of an 



