260 071 the Geography and Geology 



in irregular columnar fragments *, resembling in some degree the 

 columns of true basalt. The sandstone laps upon the granite, and 

 fits into its irregular indentations in a manner that shews it to 

 have assumed that position subsequently to the upheaving of the 

 granite. Its horizontality is perfectly preserved, even to the im- 

 mediate point of contact which is laid bare to the view. A mutual 

 decomposition for a couple of inches into each rock has taken 

 place. Dipping under the sandstone, the granite again rises on 

 the contiguous coast in high, rough, and broken hills*." Near 

 Deadman's River, and at a place fifteen miles westwards, the 

 sandstone again overlies the granite directly and horizontally. 



Point Keewawoonan, opposite the Mammelles (a district of 

 amygdaloid), and not much more than fifty miles distant from it, and, 

 at the same time, about forty miles from Isle Royale, I am told by 

 Mr. Thompson, is wholly or principally trap, simple and amygda- 

 loidal ; quite resembling the last rock at Gargantua, and containing 

 the same minerals ; as zeolite, 8;c. While circumnavigating this 

 promontory in 1 822, Mr. T. found immense quantities of pale and 

 dark green malachite in veins, and disseminated, in the rocks of 

 a bay in long. 87° 59'., about six miles west from this point. He 

 has named it Copperas Harbour. It is defended by two islets. In 

 a fine specimen, presented to me by this gentleman, the ore is in- 

 terspersed in thick coatings and plates through a dark hornblende 

 trap. I found several specimens of the same ore at the west end 

 of the Mammelles, in bowlders of sienite, very like that of the 

 casque-shaped isles of the Peek. I believe that the locality, ex- 

 amined by desire of Mr. Schoolcraft in 1823, and described by 

 him in the American Journal of Science, vol. vii. p. 45, to be Cop- 

 peras Harbour ; although this last is not exactly at the end of 

 Keewawoonan Point. The mineral brought thence by Mr. Thomp- 

 son and by" Mr. Schoolcraft's agent are the same : — and their 

 descriptions of the place correspond pretty well. Mr. Schoolcraft's 

 account is as follows : — " The precise locality of this ore is the 



* The rocks here described arc a continuation of tliose west of Michepi- 

 coton Crags. 



* Schoolcraft's Travels, p. 158. 



