The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1920-03-11
Gold Dredging---Its
History and De-
scription

.e1se s.drted mere III the cary bUs
M4ln the faced Das uetlce airedOy
mentioned. Inc spoon was empueO
mo d sluIce, All operated Dy nand
1ne canoe Nds replaced Dy pOntOOns
10 support the sIu4ces, current Nheels
tooA power from the river Itself, ana
nndily steam Upper was Invented
Gradually bucket elevator dreuges
hnally evolved there from the single
clipper dreuge. Dredging in Califor
MA seems to have evolved almost en-
tireiy independently from the New
Zealand experiments.
The California type of dredge did
not reach its present efficient and
compact design Immediately after the
Couch No 1 was constructed at Oro-
vile, California, in March, 1898. Many
OIL the early dredges aug the material
with an endless chain of buckets.
which elevated the material a certain
distance, where it was dumped and
sorted mechanically as to size, the
small material and gold falling down
into stump at water level and being
elevated again-pumped into a sluice
for washing and gold saving. This
was termed the "double-lift' type of
dredge. Also the sluices were carried
on separate barge
Today everything is seh-contained
on one barge-the excavating and
elevating machinery. the washing and
gold saving plant, and the stacker for
disposal of tailings.
Description of Modern Dredee.
In brief the standard gold dredge
of today consists first of either a
wooden or steel hull built in rectan-
gular shape with the forward corners
slightly curved Its average size is
40 to so feet wide, 100 to $50 feet long.
8 to - feet deep. This hull is cut in
two, as it were, by an opening or well
hole about 6 to feet wide, extending
from the bow half way to the stern /
Through this long opening the end
less chain of buckets travel, in their /
continuous journey around a plate |
girder frame called the digging lad
der, generally about 100 feet long. AT .
each end of the ladder is a large spool .
or tumber. around which the bucket
line travels. The upper tumblel
weighs 10 to 20 tons, and serves to
drive the bucket line. The upper end /
of the ladder is suspended at the up
per tumbler gantry 25 to 40 feet above
the deck The lower end of the lad
der is suspended from the bow gan
try by lines running over sheaves. by
means Of which the ladder and its
buckets are raised or lowered to any
depth at which it is desired to dig.
The buckets fill with gravel as they
revolve around the lower tumbler.
carry the material to the upper tum-
bier where they dump into a hopper
Here also jets of water thoroughly
clean any gold adhering to buckets to
prevent this gold from being carried I
back into the waters of the pond.
From the hopper the gold bearing
gravel or bedrock slides into a re-
volving screen. where water under
high pressure washes the clay ana
sand from the rocks, the while it is
tumbled and shaken up to disintegrate
it, The revolving screen or trommel 7
is 80 to so feet long, and feet to 10
feet in diameter, its plates perforated 4
by thousands of holes and slots, d
through which the fines pass on to the
gold saving tables. The coarse ma
terial or reject passes from the screen
on to a conveyor belt, which carries I
the gravel up a steep incline and F.,
stacks it in high piles behind the
dredge. The fine gravel, sand and
gold runs over the gold saving tables +,
or sluices, where the gold is separat-
ed by its great specific gravity and is
arrested in RIFLES aided by quicksil-
yer; the fines pass on out into the
pond well behind the dredge At in
tervals of to Is days, depending {
upon the richness Of the ground han 5
died the dredge is shut down, and the {
gold cleaned up. This is accomplish {
ed by loosening the RIFLES and knock ;
ing out the concentrates of black {
sand etc. on to the sluices where the G
is "streamed down" TO {
about one-twentieth of its former vol a
ume The heavier gold is found clean i
and ready for retortng at the upper D.
end of the tables. the finer gold is S
separated from the Fl
heavy black sand concentrate i'm a a
small sluice box equipped with ANAL n
gamated copper plate, amalgam trap
and RIFLES The gold is then retorted
to remove the quicksilver, and melteo
into bullion bars ready for shipment
to the mint
Surface to Bedrock.
The elements Of operation or dig g
ging consist Of stepping the boat for f
ward by means Of stern lines or spuds "
'or its new bite" Of or s feet into y
he gravel bank. AS the buckets start O
digging the surface the boat is swung il
slowly in the arc Of circle by means J,
IF bow lines. the port line automatic o.
lily winding up as the starboard line a
s played out. Thus a bite is taken %
IF the top of the bank 6 feet forward. q
$50 feet long and a foot or two deep n
When this is finished the ladder is T.
owered a few inches to a few feet and g