The Theory of Copper Deposition — Lane. 301 
I haw sliowii in in\- L'nitcd States Gcolog-ical Survey water 
su])ply paper Xo. 31. on the (HlYerent waters of Lower Michi- 
gan, that while each poroiis l)ccl varies in its' character of 
water from point to point, yet there is Httlc intercommunication 
between them and it is difficult to see how there could Ijc much, 
except upward alonj:^ fissures or drill holes. Beds of clay or 
shale arc known to be so impervious to water and to oil, they 
may be taken to be, even in a ideological sense, impervious 
layers, permanently guiding and separating the dififerent flows 
of water. The same statement applies to clayey belts of de- 
composed rock, paint rock and fluccan, as Van Hisc himself has 
ably pointed out in discussing chutes and the formation of the 
Galena lead deposits. Thus, it must be remembered, that Van 
Rise's figures of underground flow apply only 10 a homo- 
geneous medium. His figure 5, for instance, might represent 
the flow of water in one single porous bed, say of conglomerate, 
sandstone, or amygdaloid, but not the formation at random. 
It is by no means practically true, therefore, that the zone of 
fracture "will be searched to its base by moving waters," un- 
less first it is not only potentially but really fractured', so as to 
make it practically porous as a whole, and unless, also, it is 
covcrctl by a surface topography so rough as to stimulate 
circulation. These two conditions will be best fulfilled in those 
mountainous districts, which as Van Hise remarks, are most 
liable to contain ore deposits, page 416. 
Xow, the difficulty in supposing that the copper deposits 
are due to such a general circulation of water taken in at the 
surface, as \'an Hise imagines are very great. The following 
is a sample of water from the Arcadian shaft, a relatively shal- 
low shaft, analyzed by Dr. Koenig, August 23, 1898: 
CaCO;, 32.7 
\ Fei; O3 '. 13.7 
( Kaolin 100.0 
FeCOa 24.5 
MgCOa 25.6 
Ko CO3 10.9 
Na2 SiO;j 101.3 
Na CI tr. 
Nas P2 O5 2.2 
Nao CO3 4-2.3 
Organic matter 82.0 
Total 435.2 
