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two during the freshet. Taking the estimated amount of water available
as 990 miner’s inches, which includes the water used for a ground-sluice,
for one hundred and seventy full days in the season and 200,000 cubic
yards as the average amount of material mined, the average duty of the
water per miner’s inch a day was 1-2 cubic yards. Actually, a much larger
supply of water was used on the average during the freshet and hydraulick-
ing was done only intermittently during the dry season, but as the average
number of days during which hydraulicking was carried on and the amounts
of water used are not known, the average duty of the water per miner’s
inch, under actual working conditions, cannot be definitely determined.
It probably does not differ greatly from the amount as estimated above.
No very definite information is available regarding costs of producing the
gold. The total amount of ground mined by hydraulicking during the past
twenty years is probably at least 3,000,000 yards and the total production
is said to have been between $400,000 and $500,000. The actual working
costs of the mine probably do not exceed $10,000 a year, as only about
eleven men, on the average, are employed during the hydraulic season.
The overhead charges for equipment, ditches, etc., however, are fairly high.

The gold on Lowhee creek is mostly coarse and nuggety and is worth
about $17.25 an ounce. The gold-saving devices in the flume that has
recently been paved with steel plates, consist of riffles or spaces between
the steel plates in the upper 150 feet of the flume, of three boxes paved with
wooden blocks immediately below, and three boxes paved with wooden
blocks at the lower end of the flume. There is also a trap or undercurrent
for catching the fine gold, placed about 500 feet from the lower end of the
flume. The trap consists of a grizzly in the bottom of the flume, which
permits the fines to drop through into a large compartment beneath.
Water from a 6-inch pipe under a head of 115 feet enters the box below the
grizzly and causes an upward current which floats off the fine sand and
mud and leaves the coarse sand and gold. A take-off pipe from the main
pipe supplies water for sluicing the material which accumulates in the com-
partment or large box beneath the grizzly and which can be permitted to
flow into small sluice boxes by opening a gate. The trap appears to be one
of the most successful types of undercurrents that have been devised, the
main difficulty being that it is not automatic, but requires a considerable
part of the time of one man to operate it. Mr. Muller states that one-
half ounce of fine gold was obtained in one clean-up and that he was not
certain as yet whether the trap would pay for the time of one man to
operate it. Probably much more fine gold is lost when steel plates are
used than when the flume was paved with wooden blocks because of the
much greater velocity of the water, but in most mines in the district, as at
Lowhee, where nearly all the gold is fairly coarse, it has generally been
held that the losses were negligible. It does not appear, however, that the
question has been thoroughly investigated. In places in the district where
fine gold occurs great difficulty has been experienced in saving the gold in
hydraulic operations. It has been the general experience that unless the
grizzly and undercurrent are placed at the end of the flume so that most
of the fine material passes through the grizzly, the fine gold is likely to be
lost, for it is carried in suspension in the muddy water. But placing the
undercurrent at the end of the flume is in most cases not practicable because