304 



DESCRIPTION 



metamorphosed, however, by the trap dikes which traverse it, that it assumes a 

 trappous and amygdaloidal character, differing but little from the trap with which 

 it is in contact. The slate is dark-coloured, almost black, compact, and often crys- 

 talline in its structure. 



From the lower conglomerate beds to the main greenstone dike, the distance is 

 about two hundred and fifty yards ; and in this space the disturbance of the sedi- 

 mentary rocks is very great, the strata being broken up and mingled in the greatest 

 confusion ; the sandstone, conglomerate, and slate being thrown into a nearly ver- 

 tical position, and traversed by narrow dikes of trap, or bedded intercalations. 

 Between these dikes or beds the sandstones and shales are converted into a reddish- 

 coloured, amygdaloidal, trappous-looking rock, containing thin seams of copper ore. 

 The ore is also disseminated, to some extent, through the rocks. These metamor- 

 phosed rocks also contain narrow seams of red clay, and strings and nodules of a 

 soft, greenish, magnesian mineral, found abundantly among the volcanic grits of the 

 north shore of Lake Superior, described by Dr. Owen under the name of Thalite. 

 These metamorphosed rocks also contain epidote, and are traversed by seams of 

 jasper. 



The dike of greenstone at the Falls bears northeast by east and southwest by 

 south. Over this dike the water falls, in three cascades, one hundred and forty- 

 four feet, through a narrow, winding gorge, with perpendicular walls of rock on 

 each side. The whole fall, including the rapids above the dike, is one hundred 

 and forty-nine feet. At the point from which the first leap is taken, the channel 

 is not over six feet wide. The top of the ridge, on which Plummer's cabins stand, 

 is one hundred and sixty-six feet above the river-bed at the bottom of the Falls, 

 and commands an extensive view in the direction of Fond du Lac, and as far as 

 the culmination of the " Grand Portage " of St. Louis River. 



Twenty-five feet above the Falls, No. 491 comes in, and, for the distance of two 

 miles above, by the meanders of the river, there are exposures of altered slates, 

 intercalated with beds of trap, and traversed by dikes of greenstone, as seen in the 

 river-bed ; when amygdaloid again occurs, a short distance above the " Upper 

 Falls." At this point, the water falls over altered slate, at its junction with the 

 amygdaloid below. The river is about forty feet wide, and falls perpendicularly, 

 thirty feet, into a circular basin about sixty feet in diameter. A large mass of 

 rock on the brink of the precipice, midway the river, divides the water into two 

 chutes, and adds greatly to the picturesque appearance of the fall. A vein of 

 copper ore is said to have been discovered near the fall, and a small cabin has been 

 erected near by, for the purpose of securing the " location." 



A short distance above this, the stream is crossed by a dike of greenstone ; and 

 a little further up the river is a rapid, made by the uptilted edges of altered slate. 

 This is the last rock exposed on the river, so far as exploration was made, which 

 was for the distance of three miles above this point. Between the two falls, the 

 metamorphosed rocks lying between the trap dikes have a general dip to the 

 southeast by south, at an angle varying from 51° to 54°. The exploration of this 

 range ceased at a point about three miles west of Mashkegwagoma Lake, which is 

 the source of Aminekan or Spawn River. 



