k, Leipzig. 1879.]

[Footnote 2: Untersuchungen uber Erzgange, von Fridolin Sandberger,
Weisbaden, 1882.]

[Footnote 3: Geology and Mining Industry of Leadville, Annual Report,
Director U.S. Geol. Surv., 1881.]

[Footnote 4: Geology of the Comstock Lode and Washoe District, G.F.
Becker, Washington, 1883.

It is but justice to Messrs. Becker and Emmons to say that theirs are
admirable studies, thorough and exhaustive, of great interest and value
to both mining engineers and geologists, and most creditable to the
authors and the country. No better work of the kind has been done
anywhere, and it will detract little from its merit even if the views of
the authors on the theoretical question of the sources of the ores shall
not be generally adopted.]

The lack of space must forbid the full discussion of these theories at
the present time, but I will briefly enumerate some of the facts which
render it difficult for me to accept them.

First, _the great diversity of character exhibited by different sets of
fissure veins which cut the same country rock_ seems incompatible with
any theory of lateral secretion. These distinct systems are of different
ages, of diversified composition, and have evidently drawn their supply
of material from different sources. Hundreds of cases of this kind could
be cited, but I will mention only a few; among others the Humboldt, the
Bassick, and the Bull Domingo, near Rosita and Silver Cliff, Colorado.
These are veins contained in the same sheet of eruptive rock, but the
ores are as different as possible. The Humboldt is a narrow fissure
carrying a thin ore streak of high grade, consisting of sulphides of
silver, antimony, arsenic, and copper; the Bassick is a great
conglomerate vein containing tellurides of silver and gold,
argentiferous galena, blende, and yellow copper; the Bull Domingo is
also a great fissure filled with rubbish containing ore chimneys of
galena with tufts of wire silver. I may also cite the Jordan, with its
intersecting and yet distinct and totally different veins; the Galena,
the Neptune, and the American Flag, in Bingham Canon, Utah; and the
closely associated yet diverse system of veins the Ferris, the
Washington, the Chattanooga, the Fillmore, etc., in Bullion Canon at
Marysvale. In these and many other groups which have been examined by
the writer, the same rocks are cut by veins of different ages, having
different bearings, and containing different ores and veinsto