ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 417 - 
18), the seams and joints of which are filled with imperfectly agatized quartz, chal- 
cedony, and iron ore. The bearing is northeast and southwest, and the dip south- 
east, at an angle of 7°. A short distance below this is an exposure of quartz rock 
(No. 19), with seams of quartz running through it. The ridge immediately south 
of this is composed of hornblendic rock, like that seen on the dividing ridge. It 
forms perpendicular escarpments on the lake-shore, and is very fissile and decom- 
posible. The annexed section shows the relations of the rocks at this place. A 
en 
EK 
KN RAS 
MY WS 
a. Slaty hornblende, #. Hornblende reck. ¢. Quartz rock. 
short distance beyond this the hornblende dips to the northwest, is much contorted, 
and contains numerous thin seams and intercalations of oxide of iron. 
About one-third the distance from the lower to the upper end of the Lake, is a 
ridge of siliceous slate (No. 231), somewhat chloritic, and rising to the height of one 
hundred and fifty feet above the level of the water. It bears northeast by east 
and southwest by west. I could not discover the stratification, unless it agrees with 
the cleavage, which is 55° south of east. The direction of the joints is 35° north 
of west. 
At the bend of Flint Lake a ridge of hornblendic rock occurs, massive in some 
parts, and schistose in others. The schistose portion (No. 22) has intercalations of 
flmty seams and thin layers of iron ore. The hornblendic rocks here, like those 
seen north of Mountain Lake, have been disturbed by granitic protrusions (No. 21), 
large masses of the hornblende (No. 20) being enveloped in the granitic rocks. The 
syenitic granite rises in rounded ridges to the height of from one hundred and fifty 
to two hundred and fifty feet. It is rather coarse and felspathic, and weathers with 
a remarkably rough surface, the other constituents disintegrating, and leaving the 
quartz standing out in relief. On some of the hills the granitic rocks appear in 
sloping tabular masses, as though they had been deposited in successive beds, like 
some of the trap overflows. 
Between Flint Lake and Lake Saganaga, the rocks are all granitic, and resemble 
those already described. The stream which connects these lakes is divided into 
numerous channels, at some points, which flow around the granitic knolls, and occa- 
sionally cut gorges through them, with numerous cascades and picturesque falls. 
This range, continued in a southwesterly direction, would pass in the line of the 
Missabe Wachu and the Pokegoma Falls of the Mississippi. 
In conclusion, I may here remark that there is perhaps no extinct volcanic 
region in the world, where trap and other igneous intrusions can be studied to 
better advantage than in the country bordering on the northwest shore of Lake 
Superior. Not only are the vertical dikes numerous and conspicuous, but there 
are abundant examples of overflows, as well as interlaminated insinuations, pro- 
ducing all degrees of metamorphosis on the adjacent strata, graduating from mere 
58 
