336 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
According to the same author this series includes also detrital beds :— 
On Edward Island and other- islands northward, grits and conglomerates are 
found interstratified with trap layers. The same interstratification is met with in the 
rocks bordering the southeast side of Black bay, while those fronting the lake on the 
southeast side of the peninsula are composed almost entirely of various descriptions of 
conformably overlying trap. This arrangement of the stratification, occupying a belt 
of from seven to ten miles in breadth (which on the lake front is carved out into a multi- 
tude of deep coves, and includes a great collection of small rocky islands,) runs in a north- 
easterly direction across Neepigon Strait, from the mainland to Saint Ignace Island. 
Gradually changing its direction about the middle of this island to due east, it con- 
tinues on through Simpson’s Island, and farther to the eastern extremity of the Battle 
Islands. 
A high precipitous escarpment of red sandstone, with white bands and conglom- 
erate layers all interstratified with occasional beds of variegated red shales, and having 
a pretty constant dip of 8° or 9° to the southward, keeps its place on the north side 
of each succeeding island standing in the line, which curves a little to the south 
of eastward towards the eastern extremity. A section from the gneiss through the 
jarge center island of the Battle group would shew in place both the blue shales and 
the succeeding sandstones, apparently diminished in their proportions. In the cliffs on 
the north side of the last island of the group the limestones are displayed, associated 
with white sandstones and a conglomerate layer beneath, resting on a trap of a 
porphyritic character, and overlaid by more porous volcanic products.| * * * 
The last-named sandstones would appear to be in all probability the 
uppermost layers of the thick stratum which underlies most of the peninsula 
west of Black Bay, the sandy isthmus between Black and Nipigon bays, 
and much of Nipigon Bay itself. 
These quotations from Logan show conclusively enough that he was 
correct in placing these rocks with those of Isle Royale and Keweenaw 
Point. My own examination of this region has served chiefly to convince 
me of the accuracy of Logan’s general statements, but also enables me to 
add that the kinds of rocks here developed are precisely those which char- 
acterize the Keweenaw Series elsewhere, and no others; that Logan was prob- 
ably incorrect in supposing any of them to be hornblendic, and that while 
his statements as to dikes are generally correct, one might draw from his 
descriptions a mistaken inference in supposing that all of the prominent 
points and fringing islands of this part of the Lake Superior coast are due 
to the resistant power of dikes. Many of these points and islands are plainly 
fragments of hard and resistant layers, and often have the usual lakeward 
1 Geology of Canada, p. 78. 
