Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

GEOLOGY.
below. The south banks at this point are nearly vertical, and 2,800 feet high. A fine view of
the distant ridges of the Sierra was here presented to us. We were on Wisconsin Hill, now
being settled upon by agriculturists.
Iowa Hill, Placer county, to Nevada.1-A thick deposit of drift is found at Nevada, resting
upon a bed-rock of gray granite. This granite, as exposed by the mining operations, is very
much decomposed and softened to a great depth, so-that in places it may be removed with the
pick or shovel. These softened parts, however, contain hard, globular masses, from one or two
to over eight and ten feet in diameter. They look like great boulders, and lie thickly together
along the course of the little stream. Wherever the auriferous drift is removed the surface of
the granite is found to be very uneven, a condition which necessarily results from the manner in
which the rock decomposes, and not from abrasion or denudation.
A vast quantity of earth has been washed here by the hydraulic method. One of the principal
claims is owned by Mr. Laird, formerly of Georgia, who has made an extensive excavation
backwards in the side of a hill formed of the drift. In washing this earth, the ground-sluice
has been extensively used. They are cut in the surface of the granite and converge from the
base of different parts of the bluff until they all unite and deliver the water into a board-sluice
below. These ground-sluices are said to catch and retain the gold more effectually than those
made of boards. The gold is, however, not so readily obtained or "cIeaned up" from them.
The operations in Nature-the concentration of gold in the beds of streams, from a wide areais thus imitated by these ground-sluices.
The gold of Coyote Lead is generally in fine scales, and is poor in quality. It is said that it
is sometimes sent to the southern mines to be mixed with better gold before offering it for sale.
Water was first brought to the Nevada Hills by the Rock Creek Ditch. This was seven miles
in length, cost about $14,000, and yielded, from the sale of water, $30,000 in the first two
months. Water was sold several times over, or, rather, it was used by several parties in succession, until, from the quantity of fine slime in suspension, it became as thick as pudding, and
would no longer run. For a supply of eight inches, the first parties paid two ounces a day,
the second twenty-four dollars, the third one ounce, and so on down to four dollars. The
aqueduct was afterwards sold for about three times its original cost, and has since paid fair
dividends, even for California.2 Water is now sold for fifty cents an inch. The aqueduct of
the Deer Creek Company is said to have cost $25,000, and to have paid all the expenses of construction in the first three months.
At Grass Valley I had the opportunity of visiting several of the principal quirtz mines and
mills for the extraction of the gold. These are located along Boston Ravine, the valley of a
held by the Empire Company, chiefly composed of gentlemen from New York. Their mill is
about a quarter of a mile fromt the town, and three-quarters of a mile from the mine on " Ophir
Hill."
The rocks between the mill and the mine are not well exposed to view, being chiefly covered
by soil and a layer of drift. Neither are they seen distinctly upon the surface at the mine, but
on descending the shaft for seventy-five or one hundred feet, they are found to consist of a hard
greenatone or trap. In some places along the " ledge," or vein of quartz, it is fissile and slaty.
The ledge appears to trend north 10~ to 30~ west, and dips westwardly. Its thickness varies
The notes for this part of the trip were all lost.
2 I had these facts from a gentleman who was formerly engaged in mining near Nevada.
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