The Theory of Co ['per Deposition — l,a]iv, 299 
is just l)i.'in^- (>])i.'iu'il up ami \\li(i->c iruc value has not been 
determined. 1 1" the "high ground" notion has any 
substantial basis, its ])rosi)ects would not be so good as those 
of the Mohawk and Wolverine mines, although it lies on the 
same lode and between them. The Phoenix mine and the 
Cliff lie ou higher land, not far from the gap of l£agle river, 
and turning to the other end of the range we find the Minne- 
sota and the National on one side and the Victoria on the 
other of the gaji made by the Ontonagon river, while the Mass 
and Adventure lie on the high land between the Flint and the 
Fire Steel rivers. 
Xow, this grouping of mines in accordance with this notion 
that the copper occurs on the high ground may be due to the 
fact that the porous beds are usually eroded, and therefore 
not exposed, and not easily exploited or developed, except on 
high ground. It might also be suggested that the alterations 
which produce the copper had cemented these beds more firm- 
ly and had thus given a greater resistance to erosion, either 
by ice or by water. The copper itself, however, even in the 
richest mines, is only a small fraction of the rock, and is 
easily decomposed chemically, and so are some of the asso- 
ciated minerals, and, although at times, copper bearing amyg- 
daloids. as the igneous porous beds are called, are more or less 
saturated with silica and epidote, I do not think those minerals 
are so characteristic of the copper-bearing lodes as to lead 
to a relatively greater elevation of such parts of the lode. 
However, there is room here for inquiry. 
T leave to the last another possible explanation wbicli has 
a more direct connection with the theory of the deposits of 
the copper. If the copper is deposited by descending waters, 
as Pumpelly. who has done by far the most work upon the 
subject, suggested, and the motion of these descending waters 
is determined by gravity, descending along the lodes at one 
branch of the inverted siphon and rising either in the same lode 
at a lower ])oint of its outcrop, or in some cross fissure, which 
might very well l>e the cause of the gap in the range, then we 
can readily see that the greatest activity and circulation and 
greatest deposition of the copper consequently, should be 
beneath salient points of the outcrop of the lode. Take for 
instance, the Calumet & Hcxla. That deposit outcrops 600 or 
