302 



DESCRIPTION 



OF THE 



COUNTRY BORDERING: 



lake. On the northwest side of the ridge, this rock (No. 92), presents beautiful 

 clusters of columns, as shown in the subjoined sketch by Major Owen. They are 



CLUSTERS OF INCLINED COLUMNAR BASALT, LAKE SUPERIOR. 



mostly pentangular, and from ten to eighteen inches in diameter. The sedimentary 

 rocks near the trap dip 30° to the northwest, and the columns make about the same 

 angle with the horizon, favouring the idea that the basaltic rock is not a dike, but 

 a bed. At another point, the columns stand without order or regularity in reference 

 to the bedded rocks, and are separated from them by four feet of breccia, as shown 

 in the annexed cut, and such as is found to underlie the basaltic beds of other 



c b a d 



a. Basaltic rock, b. Breccia, c. Metamorphosed slates, d. Quartzose porphyry. 



localities. The slate within ten feet of the trap is very much altered, and resembles 

 the rock making the Great Palisades ; farther off, it becomes less and less changed, 

 softer and more amygdaloidal. The ridge which begins at this point crosses Mani- 

 tobimitagico River, about a mile above its mouth. 



d f g d abed e 



a Shale, b. Amygdaloid, c. Shaly heds. d,d,d. Volcanic grits, e. Basaltic rock. /. Breccia, g. Bed of trap. 



Half a mile farther up the Lake, the bedded rocks are very much disturbed, as 

 shown in the preceding section, and their relations obscured by a fault. 



