ISLE ROYALE TO NIPIGON BAY. 329 
probably worn out in this sandstone, of which it is supposed that only the 
uppermost parts are in sight. Good Harbor Bay, four miles below, has 
certainly had this origin, the sandstone concerned being, however, a lower 
layer. At the latter place both underlying and overlying rocks are in sight, 
the former in a low ledge on the northeast shore of the bay, the latter in a 
vertical exposure of 20 feet. The sandstone is 225 feet thick, of which 120 
feet may be measured in detail. The whole thickness dips 9° east of south. 
The Temperance River Group is almost free from dikes, another feature 
which it has in common with the bedded diabases of the upper part of the 
Keweenaw Point series. One of aphanitic black rock, six feet wide, and with 
cross-columnar structure, was noticed cutting amygdaloid near the base of 
the group on the shore at the east side of Sec. 11, T. 56, R. 7 W. In the 
same vicinity, Sec. 11, T. 56, R. 7 W., at two points, masses of red augite- 
syenite were seen in vertical contact with the diabases of the Temperance 
River Group. It is possible that these are faulted up from the under- 
lying Beaver Bay Group, though they look like cutting masses. The high 
bluff known as Carlton’s Peak, Sec. 20, T. 59, R. 4 W., near Temperance 
River, shows at its summit numerous large angular fragments of anorthite- 
rock, such as has already been described in connection with the Beaver 
Bay Group. None was seen that could be certainly regarded as in place; 
nevertheless, the mountain is, without much doubt, composed of this rock, 
and I should regard the rock as having antedated the Temperance Group 
flows rather than as a cutting mass. 
SEcTIoN Il.—ISLE ROYALE TO NIPIGON BAY. 
All along the eastern part of the Minnesota coast, as described in the 
preceding section, the Keweenawan beds strike away towards the lake 
from the coast line, so that finally, at Grand Portage Bay, the older slates 
come out to the shore. The Keweenawan beds reappear, however, in Isle 
Royale, having exchanged their easterly course for a more northeasterly 
one! while concealed by the lake. This change already begins to be per- 
1§ee the red lines of Plate XXVIII. 
