226 Notice of Messrs. Foster and Whitney^ s Report 



have tumbled from the chffs above. Still further down is to be 

 seen the rich foliage of the maple intermingled with the dark 

 green of the fir and cedar, and still beyond succeeds a level plain, 

 stretching out for twenty miles, and clothed with a dense growth 

 of trees ; while in the distance the Black river hills are seen, blue 



and indistinct, resting like a cloud upon the horizon. 



That portion of the district occupied by the detrital rocks 

 rarely rises three hundred feet above the lake. It is not unusual to 

 see ridges of sand and clay forming considerable elevations. The 

 Grand Sable is a remarkable accumulation of this character, rising 

 to the height of three hundred and forty-five feet. Point Iro- 

 quois, at the outlet of the lake, is three hundred and fifty feet in 

 height, and composed wholly of transported materials." 



There is much information in the Report on the meteorology of 

 the region, and changes of level in the lakes, which for the present 

 we pass by. Under the head of the Geology of the Copper Region, 

 the trappean and other igneous rocks come first under considera- 

 tion, 1. the ranges of Keweenaw Point ; 2. those between Port- 

 age Lake and the Montreal river, in which district the Porcupine 

 mountains constitute the highest points; and 3, those of Isle 

 Royale. In these districts, the rocks are compact trap, amyg- 

 daloid, porphyritic trap, trap-breccia, epidote trap, and com- 

 pact quartz or jasper.* Epidote is an abundant mineral. It 

 frequently accompanies the amygdaloid, and often fills the cavi- 

 ties with radiated crystallizations. It also replaces the horn- 

 blende of the trap, forming the epidote trap which is very various 

 in character; the seams of quartz and calc spar containing copper 

 are almost always accompanied by this mineral On the Uni- 

 ted States location, the trap and epidote are seen in alternating 

 bands, the cavities of the former being filled whh epidote and 

 quartz, and those of the latter with quartz and calc spar. The 

 Jaspery rock forms the highest points of the Porcupine mountains. 

 It is usually of a deep brick red color, sometimes banded like 

 ribbon-jasper, and contains seams of quartz. A quartzose por- 

 phyry has a brick-red color and contains small crystals of white 

 feldspar, not generally exceeding an eighth of an inch in length. 

 "Almost invariably, fine rounded particles of vitreous quartz are 

 found distributed through the Jaspery base. It forms an eruptive 

 mass, and often includes fragments of the pre-existing igneous 

 and sedimentary rocks." 



Besides these there is a singular rock of a feldspathic base, of 

 a light reddish color, through which irregular crystals of red feld- 

 spar and small rounded particles of quartz are discoverable, inter- 

 mixed with a greenish mineral which appears to be epidote. 



The Porcupine mountains afi'ord some copper, but there are 

 not indications enough to warrant mining enterprises. 



also 



» 



