298 The American Geologist. November, 1904. 
is the same as that of the beds of the Keweenaw formation. 
It is commonly accumulated in the originally more porous parts 
of the beds. Sometimes these porous parts are sandstones 
and conglomerates, but more often they are porous upper 
parts of lava flows. It is, I believe, true that in many cases 
there are faults parallel to the bedding planes, or so nearly 
so that the difference has not been detected, which have had an 
important influence on the production of copper. In some cases 
we know there are such faults, which generally have a some- 
what steeper dip than that of dips generally.* 
Nevertheless, in a practical way the most characteristic 
feature of these lotles is the porous beds. Any one of these 
porous beds may contain copper and there are few of them, 
which are decomposed, that do not show some trace of copper. 
But the parts which are relatively rich, rich enough to be 
the sole object of interest to the miner, are rare, and the mean- 
ing of the idea that copper occurs along high ground is, as 
I understand it, that in following the outcrop of such lode, 
chutes of copper are liable to occur where the outcrop of the 
lode is extra high. Now there is some ground for this idea. 
If we take the Baltic lode, just developed, we find that in the 
Baltic, Trimountain and Champion mines this is rich, while 
just northeast, on section i6t the Atlantic mine has done a 
good deal of exploring without being able to find the lode. 
Rising once more on the high land w^e find the Isle Royale 
mine close to the deep trough of Portage lake, Avhere, on the 
other side, is the Quincy mine, on high land again. The 
Sheldon and Columbia and Hancock mines, more down in the 
Portage Lake valley, do not appear to have been so successful. 
Going farther north, we find the Calumet & Hecla, Tamarack. 
Kearsarge and Wolverine mines, not very far from the Allouez 
gap on the southwestern side ; on the northeastern side is the 
Mohawk mine. Nearer the gap is the Ahmeek property, which 
* The top of the Calumet and Hecla is markedly slicUeusided. See also 
Volume vi Part II, pp. 86-94; the slide fault in the Central mine appears to be 
nearly parallel to the Kearsarge conglomerate. The accumulation of copper 
■was in the vein above this slide, and on reaching the conglomerate they work- 
ed on top of it finding good copper groitnd. 
The annual report of the Phoenix mine for 1901 shows in the section by 
Dunbar D. Scott, the steeper fault slide in that mine, in the St. Clair vein. 
The old Minnesota, now Michigan mine, had its largest deposit of copper 
where a steeper fissure intersected a lode. See the report of the Commissioner 
of Mineral Statistics for 1880, p. 76. Copper Handbook, 1902, p. 195. 
t Volume vi, Part II, Plate 10. 
