R. Irving—Copper-bearing Rocks of Lake Superior. 49 
of Bayfield County. Eastward of the Montreal River, in 
Michigan, the belt separates into two: the main area, which 
continues without interruption to the end of Keweenaw Point; 
and the “South Mineral Range,” which lies to the southward 
of the main belt, and follows the Huronian rocks eastward. 
The latter belt runs out in its eastern extension. Between 
it and the main area lie horizontal Silurian sandstones. 
The southernmost (111 a) portion of the group in Ashland 
County covers the broadest area. It includes rocks always 
highly crystalline, generally very coarsely so, and of such varia- 
tion in mineral constituents, texture, ete, that I have not yet 
attempted to name all the varieties, nor.even a considerable por- 
tion of them. Nearly all of them can, however, be included in 
two or three general kinds; labradorite, orthoclase, feldspar, 
hornblende, and some varieties of pyroxene, seeming to be the 
chief ingredients. The indications of bedding in this portion 
of the series are seldom to be seen, but where they are appar- 
ent, are marked, and point toward entire conformability with 
the underlying Huronian. | 
ext north of, and immediately overlying, the rocks just 
described are the beds of that portion of the group which I 
have designated 111}, c, d, on the map. ese are a series of 
alternating beds of trap, mostly melaphyres, but of very varying 
ness of sandstone and shale (111 d). ‘These sandstone and con- 
glomerate beds do not altogether overlie the trappean beds, but 
are, near the junction, directly and unmistakably interstratified 
with them. There is a sort of gradation from the trap to the 
sandstones, the layers of the latter nearest the trap being made 
up of coarse trap-sand, whilst on receding from it they become 
more and more like the horizontal aluminous red sandstones 
of the Apostle Islands. The entire series, traps, conglomerates, 
sandstone and shales, have a very high dip to the northward, 
which is never less than 85°, and often reaches the perpendicular. 
he sandstone, conglomerate, and shale beds have not as yet 
been seen west of Bad River, in Ashland County, but the 
traps can be traced uninterraptedly westward as far as 
Long Lake in Bayfield County. The traps of this group 
are also largely developed in Douglas County, and there are 
sandstone beds believed to belong to the Copper-bearing Series 
in another part of Ashland County, as will be mentioned far- 
ther on. 
4. Lower, Silurian Sandstones (Iv on the map and section).— 
North of the north line of that portion of the Copper-bearing 
Am. Jour. Scr.—Turrp — Vou. VIII, No. 43.—JuLy, 1874. 
