322 The American Geologist. November, 1905 
and minerals. The value of the book for reference is greatly en- 
hanced by a good index. The authorities quoted are up to date, 
and chosen with discrimination. 
A work of this nature will probably never be entirely free from 
inaccuracies. As an indication of conscientious work on the part 
of the reviewer and for the correction of future editions it may be 
well to call attention to a few slips: Thus, corundum is not really, 
next to diamond, "the hardest abrasive known" (p. 163). An im- 
portant use for sulphur not mentioned (p. 198) is in the manufacture 
of paper; and zinc is largely used in the cyanide process of gold ex- 
traction (p. 320). Fault planes and sheer zones can hardly be 
called "cavities" (p. 231), although they may permit the circulation 
of waters underground. This idea resembles the old notion that 
"fissure veins" were once open, empty cracks of indefinite vertical 
and horizontal extent. It is also true that "crustification" is often 
observed in veins which are not "formed by the simple filling of a 
fissure" (p. 230). 
Tellurides are not "unknown," but are often found at the con- 
tact of granitic intrusions and calcareous rocks (p. 235). 
The "apex" of a vein may not "outcrop"at all (p. 238). "Ore 
bodies lacking in iron pyrites," but composed of chalcopyrite do 
sometimes show secondary enrichment (p. 245). Some blast fur- 
naces now use more than 75% of Mesabi ores in their charge (p. 
265); and the greater value of hematite ore is not due so much to 
its proximity to theoretical purity as to the readiness with which 
it is reduced by carbonaceous fuel as compared with magnetite (p. 
252). 
Altered copper ores are not usually more cheaply treated than 
sulphide ores, and chalcopyrite is not commonly considered a sec- 
ondary ore (p. 2S1). 
The large copper mines at Butte are from 2000 to 2500 feet deep 
instead of 1000 to 1500 and the vertical limit of the silver ore was 
determined long before the silver mines reached the depth of 1400 
feet (p. 286). Douglass Houghton was an "A. B." and "M. D." and 
a geologist, but it is novel to hear him called "a mining engineer" 
(p. 287). Copper in the Lake Superior region is seldom if ever 
"refined electrolytically" (p. 290). 
Sulphide of gold is certainly a rarity (p. 329) ; but so are really 
well-balanced works on economic geology in general. And the con- 
clusion should not be drawn from the above series of minor correc- 
tions and suggestions that this is not a very valuable and useful 
addition to our literature on the subject which it treats. Necessa- 
rily condensed, it yet covers the ground in a thorough and authori- 
tative manner and will be used by many as the most satisfactory 
text book available. H. .V. W. 
