48 R. Irving—Copper-bearing Rocks of Lake Superior. 
Gogebie, where the rocks are lost sight of, being covered by 
8g 
siliceous schists, black slates of undetermined composition, 
white quartz rocks, quartzites, magnetic and specular schists of 
various kinds, magnetic and specular iron ores, diorites, diorite 
slates and diorite schists, The be 
north, generally at a very high angle. The thickness never 
varies far from 4,000 feet, a figure obtained by actual measure- 
have—including all subdivisions—an apparent thickness of as 
much as four miles, and even more th 
east. These rocks form a broad belt in Ashland County, which 
is widest at its eastern end, narrowing toward the west, and at 
the same time receding from the lake shore. The most westerly 
known portion of the belt is at Long Lake, in the southern end 
8S Ge aeRO a ae aeiaghce s See Ae 
