1852.] BIGSBY GEOLOGY OF THE LAKE OF THE WOODS. 403 



With regard to the metamorphic rocks, the gneiss is only the gra- 

 nite interleaved with mica, and so rendered more or less slaty. Its 

 mineral changes are similar to those of the granite. 



Gneiss occupies the whole western shore of Lake Kaminitic up to 

 near the River Winnepeg, and is also the frequent associate of granite 

 in other parts of the lake. 



Mica- slate is found extensively on the south shore of the Promon- 

 tory and in the islands off Shebashca. It passes into and is inter- 

 leaved with gneiss and a very black trap. 



Greenstone is perhaps the most abundant rock in Lake Kaminitic. 

 It is commonly impregnated with chlorite ; but the proportions of this 

 earth vary insensibly. Where there is much, it is in fine, shining, 

 wavy or very tortuous foliations, interspersed with small nodules of 

 the rock in concentric layers. This is well seen on the north-east shore 

 five miles from the Rat Portage. The greenstone is very chloritic at 

 intervals along the north side of the great Promontory, and especially 

 on some islands near the Isle of the Yellow Girl. On these islands 

 are veins of chlorite-earth 6-9 inches wide, used by the Indians for 

 making pipe-heads. When the rock is less charged with chlorite it 

 becomes almost massive. In several places for some square miles 

 along the eastern shore of Kaminitic (as for instance a few miles 

 north of Anagoyahme River), the greenstone is rendered porphyritic 

 by the presence of crystals of white felspar ; and in some districts, 

 each from 5 to 6 miles in length, along the north shore of the Pro- 

 montory, from Red Cliff Bay to the Portage des Bois, it might be 

 called syenite, on account of the gradual introduction of innumerable 

 beads or drops of glassy quartz. 



Greenstone- conglomerate appears twice in Kaminitic, but not under 

 the same conditions. The northern band stretches E.N.E. from an 

 island near the River La Platte, on the west shore, to the corresponding 

 point on the north-east shore. On this island it wears a peculiar 

 form. It contains many round black masses of the size of pigeons* 

 eggs, like Lydian stone, and as hard and close in texture ; but the 

 great body of the rock is made up of large, oblong, angular masses 

 of pale speckled greenstone, which lie with their length parallel to 

 the strike. These appear on the weathered surface of the rock, but, 

 on breaking it up to obtain specimens, they are seen to pass into a 

 slaty structure, and become continuous with the cement of the con- 

 glomerate, as in Lake Superior, &c. 



The chloritic greenstone-conglomerate about Portage des Bois, 

 south of that just described, occupies a space twelve miles long north- 

 wardly, by six broad. Both the nodules and the paste are green- 

 stone ; the latter is darkest in colour. The nodules are here rounded, 

 and vary in diameter from 1 to 15 inches. It was curious to observe 

 that many of them were broken into several fragments from the 

 effect of heat or by some external force, which however had not 

 widely separated them (see fig. 2). 



Proceeding now to Sandhill Lake, we observe how regular, and 

 often how minute, are the interleavings of gneiss, mica-slate, and dark 

 compact greenstone along the greater part of the Promontory and its 



