JV. W. Portion of Lake Huron. 259 



gneiss having a northern direction, and the trap a south west 

 course. 



These last named rocks are distinctly primitive, and are 

 supported on the north and north east by others of that or- 

 der, as for instance, for thirty-seven miles further to the east 

 is a large trappose* formation, at the west end passing into 

 greenstone, but at the eastern being nearly a pure horn- 

 blende, highly crystalline, and rising in precipices which 

 reflect a metallic lustre in certain positions. The islands of 

 La Cloche are of this substance, which occasionally be- 

 comes a clinkstone, and has given to this picturesque cluster 

 its present name. 



The rocks for two hundred miles to the north east of this 

 spot are, with the exception of a little white marble, invari- 

 ably small grained quartzose gneiss. 



Having now cursorily noticed the geology of the country 

 in connection with the transition rocks of the north v/est por- 

 tion of Lake Huron, I shall enter upon their description. 



A greenstone in various modifications occupies the north 

 main, from Ion. 82° 42' to the head of the Narrows of St. 

 Joseph, a distance perhaps of twelve miles. In the exten- 

 sive marshy bay, east of the broad promontoryf in the mid- 

 dle of this distance, this rock forms islets (either barren or 

 fringed with a scanty vegetation,) rising from the water in 

 round and smooth ridges. It is the same here as at the low- 

 er end of the promontory, where it is a dark greenstone, 

 very compact, yet shewing a schistose tendency in its weath- 

 ered portions. It is rather thickly studded with rolled 

 masses of from one to eighteen inches in diameter, of the 

 red granitous ingredient in the Serpent rock — a curious fact. 

 In some parts of this headland these fragments are so nu- 

 merous as to give to the rock the character of a conglome- 

 rate ; the imbedded substances being a large proportion of 

 the whole. 



They disappear gradually, but entirely or nearly so, and 

 the form of a splintery greenstone slate is now and then as- 

 sumed, differently colored, commonly of a dark leaden blue, 



* With a south west direction and vertical. Among them at one place I 

 observed a few granite strata running north. 



t The want of appellations for the different localities is severely felt ia 

 speaking of unfrequ-ented countries. 



