ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 415 

 Another example of a slate escarpment, with its talus, is exhibted in this cut. 



The long point below the mouth of Arrow River is composed of a fine-grained 

 hornblendic rock, with a slaty structure. It splits into thin layers, and is regularly 

 jointed. On the gentle slope to the lake, where it is bare, it presents the appear- 

 ance of a tessellated pavement. At the west end of the lake is a ridge four hundred 

 and fifty-nine feet in height, the lower part of which is composed of argillaceous 

 slate (No. 25). It dips southeast, into the side of the ridge, at a high angle. East 

 of the slate-beds is a high ridge of syenite (No. 26), which extends to the margin 

 of the lake, and forms mural precipices on the hillside. The upper part of the 

 ridge, and near the hill over which the portage to Wisacode River passes, the rock 

 becomes fine-grained, and is jointed (No. 28). The succeeding ridge, which comes 

 to the lake opposite the point above the mouth of Arrow River, is finer-grained and 

 presents a slaty structure. It resembles slaty greenstone (No. 29). The following- 

 section illustrates, partially, the relations of the rocks here. 



ti' a b 



a. Clay slate, b. Syenite, c. Porphyritic greenstone, d. Hornblendic rock. a'. Slaty greenstone. 



About a mile from the east end of Mud Lake, a small stream conies in, on the 

 south side, and immediately west of it the portage begins which leads to a small 

 lake tributary to Wisacode River. The portage is about a thousand yards long, 

 and crosses a ridge over three hundred feet in height. The stream just before 

 entering the lake has a fall of sixty feet, in a series of beautiful cascades. 



At some points the high ridges have a long slope to the lake-shore, covered with 

 vegetation, which, with the talus at the base, conceals the rocks nearly to the sum- 

 mit, when they mount up in high escarpments, as represented in the sketch, by 

 Major Owen, on page 416. 



The twelfth portage is four hundred and forty paces in length, and leads over a 

 low ridge, with numerous boulders of syenite, gneiss, and granite, scattered over it, 

 to Ashawiwisitagon Lake. The ridge is composed of a syenitic rock (No. 24), 

 underlying hornblendic slates, at the west end. On the shores of Ashawiwisitagon 

 Lake, there are constant exposures of metamorphic slates, in low ledges, rising only 



