80 DIFFERENT METHODS OF MINING.
they are separated only with difficulty by the present process of washing.
S.
B. Christy found that the gold amalgamates easily, but that the finer
particles, when once allowed to dry, seem to become covered with a film
of air and to float readily on subsequent immersion in water.
Prof.
J. D. Dana considers that these deposits date from the close of the
Glacial, and partly from the latter half of the Champlain period.
As
the tides continually alter the position of the exposed auriferous
layers, it is necessary to prospect every day for the richest spots,
which are generally covered at high water. At low tide the miners
proceed to the localities selected, scrape up the thin gold-bearing
strata, and transport the material to the washing place. The washing
is generally done in sluices, to which are attached various gold-saving
contrivances.
It
is claimed that much of the sand assays from $10 to $30 per ton, and
that very large amounts assay from $5 to $10, only a part of which,
however, is saved. Skidmore states that the variable character of the
sands prevents beach-mining enterprises from being carried on
successfully for any length of time.
Bar and River Mining.—In
early days river-mining was extensively carried on. The discovery of
rich bars caused many excitements. It led to the rapid exploration and
settlement of large areas of country, and was generally the first step
towards opening up the gold-mining regions.
The
portions of the bars above water-level being soon exhausted, the
miners' attention was naturally led to the exploration of the parts
under water. Streams were dammed and turned into new channels, often at
enormous costs and risks. The beds of rivers for considerable distances
were laid bare while the miner worked his claim. This class of mining,
apart from the danger arising from floods and breaking of dams, had in
it a factor of uncertainty—
