segregated
veins of the Alleghany belt and the gash veins of the Mississippi
region--and in other cases--where they are contained in true fissure
veins--from a foreign source, but all deposited without the aid of
superficial igneous rocks, either as contributors of matter or force.

2. In the great mineral belt of the Far West, where volcanic emanations
are so abundant, and where they have certainly played an important part
in the formation of ore deposits, the great majority of veins are not in
immediate contact with trap rocks, and they could not, therefore, have
furnished the ores.

A volume might be formed by a list of the cases of this kind, but I can
here allude to a few only, most of which I have myself examined, viz.:

_(a.)_ The great ore chambers of the San Carlos Mountains in Chihuahua,
the largest deposits of ore of which I have any knowledge. These are
contained in heavy beds of limestone, which are cut in various places by
trap dikes, which, as elsewhere, have undoubtedly furnished the stimulus
to chemical action that has resulted in the formation of the ore bodies,
but are too remote to have supplied the material.

_(b.)_ The silver mines of Santa Eulalia, in Chihuahua, from which
during the last century one hundred and twelve millions of dollars were
taken, opened on ore deposits situated in Cretaceous limestones like
those of San Carlos, and apparently similar ore-filled chambers; an
igneous rock caps the hills in the vicinity, but is nowhere in contact
or even proximity to the ore bodies. (See Kimball, _Amer. Jour. Sci,_.
March, 1870.)

_(c.)_ The great chambers of Tombstone, and the copper veins of the
Globe District, the Copper Queen, etc., in Arizona.

_(d.)_ The large bodies of silver-ore at Lake Valley, New Mexico;
chambers in limestone, like _c_.

_(e.)_ The Black Hawk group of gold mines, the Montezuma, Georgetown,
and other silver mines in the granite belt of Colorado.

_(f.)_ The great group of veins and chambers in the Bradshaw, Lincoln,
Star, and Granite districts of Southern Utah, where we find a host of
veins of different character in limestone or granite, with no trap to
which the ores can be credited.

_(g.)_ The Crismon Mammoth vein of Tintic.

_(h.)_ The group of mines opened on the American Fork, on Big and Little
Cottonwood, and in Parley's Park, including the Silver Bell, the Emma,
the Vallejo, the Prince of Wales, the Kessler, the Bonanza, the Climax,
the Pinon, and th