264 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
the dip remaining at 15° S. E. From Duluth to French River the coast line 
trends about N.50° E., so that in this distance the rock beds, running more 
to the north than the coast line, intersect it at an angle which varies from 
55° near Duluth to nearly 0° at French River. One interesting result of 
this relation between the trend of the strata and that of the coast line is the 
production of points projecting southwestward and formed of the harder beds. 
It is these projecting points, with other smaller ones along the Minnesota coast, 
that have been represented by Norwood as formed of a series of dikes. As 
shown below, dikes exist here, but they are relatively very infrequent, and 
nearly always of small thickness. From Duluth to French River, then, 
there is a constant ascent in geological horizon, and the thickness crossed 
cannot be much less than from 8,000 to 9,000 feet. 
From French River to Burlington Bay there is again a somewhat 
more northerly trend in the rock beds, but since the coast line here also 
runs more around to the north, the dips at the same time flattening to 10° 
and even 6°, there is not much added in this distance to the thickness above 
given. After Burlington Bay is passed, the strike begins to cut the coast 
more sharply, and by the time Split Rock River is reached, 45 miles below 
Duluth, fully 10,000 feet of thickness have been crossed. 
In the vicinity of Split Rock River the layers strike nearly due north, 
cutting the coast at an angle of 35°; but half way between Split Rock 
River and Beaver Bay, coast and strata are again trending together, at 
about 40° east of north. Below Beaver Bay, again, the strata turn away 
from the coast to the northward, and for some two miles below Baptism 
River strike only a very few degrees east of north, and by this time the 
coast must have crossed fully 16,000 feet in thickness of rock beds. Be- 
yond the last point, however, both coast and strata begin curving more and 
more around to the east, the two coinciding at N. 50° E., somewhere 
between Petit Marais and Two Islands River. In the vicinity of Two 
Islands, Cross, and Temperance rivers, are the highest strata met with 
anywhere on the Minnesota coast, or, indeed, on the entire north shore of 
the lake, with the exception of Isle Royale. In the 80 miles between 
