R. Irving—Copper-bearing Rocks of Lake Superior. 47 
I. Age of the Copper-bearing Series. 
. 
the conclusions toward which they seem to point. 
and slates of the Copper-bearing Series; and Lower Silurian 
sandstones. Besides these there are trap! thick deposits 
Dr 
¥* This Journal, June, 1872. : 
_ + T. B. Brooks, “Geology of Upper Peninsula,” 1873. 
