REVIEWS 437 
ground waters, the material being gathered from the rocks through 
which the waters pass, and that the sulphide ores are formed princi- 
pally by the returning or ascending portion of the circulation. This 
conception, amplified and defended with many arguments and 
examples, is the keynote of the paper by Van Hise, which forms the 
natural beginning of the second part of the volume. Since Professor 
Van Hise’s views have already been presented in this JOURNAL, no 
review of them need be made here. 
The criticism of Van Hise’s views has been principally along two 
lines: (1) Is the conception presented by him of a universal under- 
ground circulation moving in obedience to gravitative stress a true 
one ? and (2) is such a circulation competent to account for ore bodies 
such as actually occur without calling in the very frequent and active 
agency of eruptive forces? It appears to the reviewer that, to a con- 
siderable extent, the criticism is based upon an erroneous understand- 
ing of the hypothesis, and to a minor extent upon a misconception 
of facts. A universal underground water circulation does not neces- 
sarily mean universally saturated rocks. The great difference in 
permeability of rocks precludes their having an equal water content. 
If a larger emphasis be placed upon the influence of impervious 
strata, the supposed difficulties largely disappear. Professor Kemp 
cites a number of deep workings which are dry (696-701), and states 
a belief that the amount of water which penetrates to depths is prob- 
ably comparatively small. Such citations, however, are only signifi- 
cant when the full details of each case are fully understood. For 
example, the Congress mine in Arizona has been cited, by another, 
as an instance of a very deep mine which is notoriously dry. The 
illustration loses its force, however, when it is remembered (1) that 
the region is one in which the water level is everywhere far below 
the present surface, and (2) that the Congress vein is a very shallow 
dipping one. ‘‘ Very deep,’ as measured along the vein, is, accord- 
ingly, not ‘‘very deep” as measured vertically. Again the Vindicator, 
Hull City, and neighboring mines at Cripple Creek go down a thou- 
sand feet or more in perfectly dry ground, but they start only a short 
distance laterally, but at a considerable altitude above Wilson Creek. 
Furthermore, anyone visiting the workings will at once see the 
clearest evidence of the former action of underground waters; in this 
case evidently oxidizing surface waters. 
‘Jour. GEol., Vol. VIII, pp. 730-70, 1900. 
