OF THE ROCKS OF LAKE SUPERIOR 



253 



clu Lac, and on Portage Creek. Colour, reddish gray. It appears to be composed 

 of hornblende, quartz, and flesh-coloured felspar ; the last-named constituent so pre- 

 dominant as to give colour to the rock. The hornblende and quartz are granular ; 

 the felspar in small segregations. In general aspect, it bears great resemblance to 

 the altered sandstones found on Black River, the Wisconsin, and on the Mississippi. 

 It weathers with a very rough surface, is cavernous, and slightly nesty. It is com- 

 pact, heavy, and breaks with a regular fracture. 



591. Bears N. 14° W. Porphyry. The base seems to be granular felspar and 

 magnetic oxide of iron. The embedded crystals are numerous, and of a dirty white 

 and light flesh-colour. The base is of a dark colour, and has a rough, irregular 

 fracture. It is very compact, and, except in colour, bears strong resemblance to the 

 " Great Palisade" rock. It is an overlying rock at the second point below the " Entry 

 Point," and occupies, no doubt, the same place in the series as the Palisade and 

 other siliceous porphyritic rocks of the middle and easterly portion of the District, 

 which rocks have been placed among the metamorphosed siliceous and argillaceous 

 slates. This is the same rock as No. 421 of the Kinechigakwag Creek series, and 

 as No. 590, though this last is not magnetic. These porphyries are magnetic, and 

 contain a great deal of epidote in the joints, and probably some chlorite dissemi- 

 nated through them. The dip at the place where this specimen was taken is 18° 

 S. E. No. 591 is jointed, and some of the joints present a rusty colour. Weathers 

 with a smooth surface. Is traversed by No. 592. The trap is magnetic, and the 

 probability is, that the dike has conferred no property on the metamorphosed rock 

 which it does not itself possess. This rock comes to the Lake again in the third bay 

 east of the Entry Point, where it seems to bear N. 45° E. This change of dip is, no 

 doubt, owing to the difference in bearing of the intrusive rocks. 



592. Bears N. and S. Basaltic greenstone — homogeneous ; very fine granular. 

 Colour, very dark gray-black, on the weathered surface, which is smooth and even ; 

 joints with a thin coat of iron-rust. It is slightly magnetic. This is the character 

 of most of the narrow dikes in this vicinity. 



593. Porphyry — like No. 591. Has less of the trappous appearance; is very 

 compact ; numerous crystals of deep flesh-coloured felspar ; some few small segre- 

 gations of the same. Would make a beautiful rock for ornamental purposes. It is 

 magnetic, like No. 591. Has a tolerably even fracture. Weathered surface smooth, 

 the paste and embedded crystals seeming to wear equally. Contains some epidote. 

 Belongs to the Kinechigakwag Creek beds. It is possible that No. 591 may be a 

 narrow dike, through which much of the material of this rock was erupted, and 

 may bear an analogy to the Anorthite rock in the region of the Palisades. The 

 paste, which is very fine, has a dark reddish tint, and contains numerous minute 

 grains of magnetic oxide of iron, in which respect it bears a strong analogy to some 

 of the fine-grained argillaceous grit beds. It is magnetic. 



594. Bears N. 30° E. Greenstone. Rather more coarsely crystalline than No. 

 589. Colour, grayish green. Some of the felspar green ; some of it inclined to a 

 flesh colour. Is jointed ; one set of horizontal joints dipping regularly to the S. E. ; 

 another set, W. 15° N. ; and a third set, N. and S. These last are perpendicular. 

 Has an irregular fracture. Iron-shot in the joints, and partially so on weathered 



