L E F T-flAND AND BLACK RIVERS. 



303 



Me-kud-d-dbi, or Black River, is a small stream, emptying into Left-hand River 

 from the southeast. Its waters present a striking contrast to those of Left-hand 

 River. They are entirely free from sediment, and so limpid, that in the shadows 

 of the hills and trees they appear perfectly black. The stream is too much ob- 

 structed by drift-wood near its mouth, and too shallow higher up, to be navigable 

 for canoes. I therefore pitched my tent near its mouth, and proceeded to explore 

 it on foot. About eight miles above the mouth, following the windings of the river, 

 red sandstone shows itself, in place, at the water-level. It is in thin layers, from 

 an inch and a half to eight inches thick, banded with red and grayish stripes, and 

 dips northwest at an angle of 14°. (See Section from the Valley of St. Croix R. to 

 Rainy Lake, PI. 2, N., Sec. 2.) The intervening country is hilly; the general 

 bearing of the ridges being northeast and southwest, with occasional spurs bearing- 

 easterly and westerly, and north and south. The deposits in this distance are : — 



1 . Alluvion ; 



2. Red marl, with boulders; 



3. Red clay ; 



overlying a deposit of red and drab-coloured sandstones. 



The upper beds of the sandstone are buff-coloured ; made up of rounded grains of 

 quartz, well cemented ; rather coarse-grained ; compact ; and when exposed to the 

 influence of the atmosphere for some time, acquire a reddish tint externally. The 

 lower beds are of a beautiful maroon-colour, Avith irregular grayish bands and 

 points ; fine-grained, with an occasional coarse grain ; tolerably coherent ; and 

 marked with fine parallel lines of deposition. 



The rock rapidly thickens to forty feet, overlaid by heavy clay and marl beds, 

 and continues to increase in thickness up to the metamorphosed and trap rocks. As 

 these last-named rocks are approached, the sandstone acquires a dark reddish-gray 

 colour, is thicker bedded, harder, better cemented, weathers well, and would 

 make an excellent building-stone. Beneath these beds it becomes thin and shaly, 

 and contains small gravel, and is, finally, intercalated with beds of conglomerate. 



The sandstone is underlaid by a coarse conglomerate, which, at a distance from 

 the trappous rocks, is loosely cemented, and weathers easily. It is made up of red 

 sandstone, quartz, jasper, and clay-slate pebbles, most of them rounded, and many 

 of the quartz pebbles polished. By far the greater portion of the pebbles, however, 

 are derived from the red sand-rock. Those from the slate have assumed the pre- 

 vailing red colour. Some of the quartz pebbles are from three to four inches in 

 diameter. 



Where the sandstone and conglomerate approach the trappous rocks, they are 

 altered both in texture and colour. The sand-rock acquires a dark brown colour, 

 and is converted into a true quartzite, exceedingly hard and compact ; while the 

 siliceo-argillaceous cement of the conglomerate is similarly affected, but without be- 

 coming more firmly united with the contained pebbles. Nos. 483 to 487, show the 

 degrees of change produced by the intrusion of the trap dikes. 



Below the conglomerate, an altered argillaceous slate comes in, so completely 



