176 The American Geologist. September, 1892 
of the chert, in some of the less ferruginous parts of tlie forma- 
tion, is hardly sufficient to account for such a vast deposit of iron 
ore. It seems like trifling with the problem to appeal to such a 
cause for the ore. 
4. As to concentration by decay of ferruginous schists — the 
process seems to have been the reverse, viz. , from the ore has 
been diffused iron oxide through non- ferruginous schists, so that 
for several feet from the ore the surrounding rock is stained a ver- 
milion or brownish red This has not only affected some of the 
green schists, but also some of the underl3'ing quartzyte. And 
again, on the theory of ferruginous concentration from schists, or 
from any rock, it is necessary to explain the singular fact — singu- 
lar under that hypothesis — of the occurrence of the ore always at 
the same stratigraphic horizon in the same formation. Why 
should not this ore accumulate, at least sporadically, at some 
lower or slightlj' higher stratigraphic horizon? Here we find it, 
for 150 miles, maintaining its position in the series as constantly 
as any of the beds that are associated with it. 
5. The absence of dykes of irruptive rock. These have been 
supposed to have played an important role in the concentration of 
the hematites of the Penokee range, on the south side of lake 
Superior. Yet, on the north side but one such dyke has been 
discovered, and that is in the eastern extension of the iron range 
where, notwithstanding a year's costly exploration in the vicinity, 
no hematite has yet been found in commercial quantities. At the 
western end of the range, where the recent discoveries have been 
made, not a single dyke has been discovered. Further, the strata 
that enclose the ore are not impervious, and could not form 
troughs, bj' any combination of dyke and dip, but the underlying 
rock is a loose white sandstone. It has sometimes become deeply 
stained by the downward percolation of surface waters carrj'ing 
the ore mechanically amongst its rounded grains. 
6. There is an apparent extensive change in the rock of the coun- 
tiy. The details of this change cannot be given here. As one 
stands at the brink of one of the excavations and sees distinctly 
a sweep of plainly originally sedimentary layers, across the face 
of the cut, manifesting all the usual characters of sedimentation, 
and reflects that the strata which he now beholds consist of bes- 
semer hematite, slightly brecciated, soft, easily mashed, he is 
driven to one of two conclusions — either, first, that the ore was 
deposited as a constituent part of a sedimentary series, or second, 
