of Lake Superior 245 



strike the eye instantly from the prolonged black or iron-rusted 

 channel of iindeviating course they trace among; ruinous and dis- 

 ordered rocks. Their very various directions, and the hilly nature 

 of the region they pervade, prevents the same individual from 

 being noted through a great distance, but, occasionally, as 

 eight miles west of the Otter's Head, near the Great Written 

 Rocks, and about Cape Verd, they are seen continuously for a 

 mile, and when lost in the lake on one side of a bay, they often 

 emerge at the point on its opposite side indicated by the direction 

 of the vein. They intersect eminences 350 feet high, like a flight 

 of steps, and thus offer the best (though hazardous) mode of ascent, 

 as at five miles east of the Lesser Written Rocks. The passage, 

 from one rock-deposit to another, affects neither their direction, 

 inclination, size, nor composition. 



The breadth of these veins varies from a few inches to 60 feet, 

 these extremes, and the intermediate dimensions, also being 

 common. Their sides are usually parallel, but close inspection 

 always detects small angular projections into the inclosing rock. 

 Frequently these are considerable and singular (vide fig. i. and 

 fig. V*.) ; at other times they are large formal wedges. In fig. vi. 

 (same plate) sudden changes of width take place without the 

 parallelism of the sides being much disturbed. Fig. vii. is an 

 example of the lenticular expansion which sometimes occurs : — 

 here it is in two contiguous veins. This sketch also offers an 

 example, not unfrequent, of a slender tapering mass of granite 

 having insinuated itself into the vein. A still more common fact 

 is the needle-formed slip of basalt (if I may be allowed this name) 

 often projected into the granite. These veins occasionally taper, and 

 almost always are accompanied by one or more branches, which 

 diverge a little, in a serpentine or straight line, from the direction 

 of the parent trunk. It is not uncommon to see large veins sub- 

 dividing suddenly into a number of ramifications. 



Angular masses of the imbedding are sometimes met with in 

 the vein as in the instance sketched in figs. ii. and v. A vein, 



* Of the annexed wood-cuts. 



