ON THE NORTHWEST 



SHORE OF LAKE SUPERIOR. 407 



the slates have no perceptible dip. Between the two falls, the argillaceous beds are 

 extremely fissile (No. 12), for the height of fifteen or twenty feet above the river- 

 level, and then become gradually more and more altered, until they assume a 

 columnar structure as the greenstone-bed is approached, as shown in the second 

 section on this page. 



The section below is among the very few where any certain connexion was seen 

 between the overlying trap-beds and the large dikes. The dike, which traverses 



a. Argillaceous slate, b. Metamorphosed slates, c. Bed of greenstone, d. Greenstone dike. 



the slates at this place, and sends off the sheets which overlie them, has produced 

 little or no disturbance, except at the junction. A section of the rocks here, in 

 ascending order, is as follows : 



1. Quartzose schists (No. 1). 



2. Clay slates (No. 8), alternating with i[uartzuse layers. 



3. Hornblendic schists (No. 9). 



4. The same rock (No. 10), passing into greenstone. 



5. Greenstone (No. 11), forming the dike and the overlying beds. 



The thickness of the metamorphosed beds in this section is forty-five feet. Below 

 the dike, the beds have no perceptible dip ; above it, they dip to the northwest, at 



a. Argillaceous slate. 



b. Metamorphosed slate. 



Cj c. Greenstone, dike and bed. 



(/. Quartzose porphyry. 

 e. Spar Tein. 



an angle of 5°. About two hundred yards further up stream is another dike, 

 which appears to have been erupted at the same time with the one last-named, as 



