342 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
About three-fourths of a mile out in front of the harbor, which is half-way down 
the south side, a few narrow islands occur, presenting beds of peculiar character, 
amounting to between sixty and seventy feet, dipping southward at an angle of twenty 
degrees. They are of a general red color, spotted and patched with yellowish-white, 
and wherever a crack exists the rock is blanched to a small distance on each side of 
it. The surfaces are uneven, and peculiarly marked with festooned and finely wrinkled 
forms, composed of very thin close-fitting lamine, with a ligneous aspect, having a 
thickness sometimes exceeding one or two inches. The rock scarcely resembles a trap, 
nor does it bear the character of indurated shale; but it may perhaps be an indurated 
mixture of voleanic mud and ashes, in which the wrinkles result from a partial flow. 
The total volume of the formation developed in Michipicoten Island at the most mod- 
erate dip observed would not fall short of 12,000 feet. 
Subsequently to the publication of this description of the Michipicoten 
rocks Macfarlane made a further study of them for the Canada survey. 
His more detailed examinations established a total thickness of over 18,500 
feet of plainly bedded eruptive flows, with interstratified conglomerates 
and sandstones. From the numerous dip and strike observations which he 
records, it is evident that the beds throughout the island have, as Logan says, 
a southerly dip, but also that they take a sort of curving course as they are 
followed on the length of the island, the strike directions becoming more 
and more north of east as the eastern end of the island is reached. The dip 
also flattens to the southward, the beds on the north side of the island 
dipping south as much as 30° to 36°, while on the south shore the angle 
appears to be often less than 20°. Macfarlane also describes the existence 
on the east and northeast shores of the island of peculiar masses of red 
quartziferous porphyry, which occur in confused relations to the associated 
basic rocks, the very regular succession of beds seen on the east and south 
sides of the island failing to repeat itself here. 
By the kindness of Mr. A. R. C. Selwyn, Director of the Geological 
Survey of Canada, I am in possession of a suite of nineteen type specimens 
of the Michipicoten rocks, collected and determined according to the older 
lithological methods by Mr. Macfarlane. These I have carefully studied 
under the microscope, and am thus the better able to institute a satisfactory 
comparison between the Michipicoten rocks and those of the typical Ke- 
weenawan localities of the South Shore. 
The peculiar red- and white-blotched, wrinkled rock described by 
Logan as forming the small islands which lie about three-fourths of a mile 
