The San Francisco call., 1899-04-10

a costly and risky operation which can
be conducted but small part of the
able. Bedrock, where the greatest riches
lie, is often buried many feet deep, in
places nearly a hundred feet and in
others but five or ten. one OF the notaple
mining enterprises of the State IS the
turning of the Feather wholly out of its
bed. A successful gold dredge works
such river beds to bedrock and gets a
considerable percentage of the gold lying
on the bedrock and in it's shallow crevices
and can operate all the year. Many de-
posits have been worked only TO the
water line.
But the greatest amount of gold-bear-
ing gravel is in the benches fanking the
streams and in old channels, bars and
basins. There is an immense area OF
such ground averaging moderate values
of few cents cubic yard through
many feet of depth and often rich near
bedrock The only economical method
of working such ground has been the
hydraulic process and as thousands of
acres of such ground lie where the
hydraulic process cannot be used, the
gold still waits extraction. A properly
designed gold dredge will work such de-
posits at. cost. of from to cents
cubic yard, or as cheapy per yard as a
hydraulic plant would work ground: As
vast areas of ground will average ~ 10
20 cents or even more the opportunities
are evident.
California. which has led the world in
quartz mining, is late in getting around
10 IIlS form OF the IIllIlIlS lIlQuSlIS. II
began in New Zealand in the early days
of mining there, has reached its highest
development there, and the world turns
to New Zealand to learn the business.
There has been steady evolution OIL
the gold dredge since then until now IL
is one of the chief features OF the New
Zealand mining industry On the CIutha
River in the province OF Otago on the
southern island there are seventy-hNe
dredgers, and there are perhaps hum
dred more elsewhere in New Zealand.
In quite recent years the success at
tanned in New Zealand has attracted at
tention throughout the world, and New
Zealand methods have been the subject
of much inquiry, report ana discussion IN
Australia South Africa, Siberia, Canada,
the United States and elsewhere. Dredges
are now being built or contemplated III
every auriferous region Of the world
Gold dredging in California may be SAID
to have started about five years ago, when
the Diestlehorst Brothers OF Redd1ng
rugged up a primitive contrlVance ana
went to working the bed of Lower Mlddle
Creek above Redding. 1t was a pecuIar
shaped scoop, holding One-third OF CUBIC
yard, and operated on pontoon by a
steam winch al ope end, when Dragged
the scoop along the bottom quite like the
first New Zealand plant. But it paid, and
the Diestlehorsts planned larger steam
power scoop dredge OF anQIneI S1 5tSIe 1,iIt ait
built it on the klamath. Then they pullt
another and the two Dlestlehorst dredgeS
are now operating at Big OAK Bar on the
Klamath A similar dredge of compara-
Upper Sacramento two or three years ago
by others, and then somebody installed on
that stream a dredge of the clam shell
type No definite information as to cost
Cf operation or profits of any OF these
dTedges has been given, but they work on
and evidently pay.
here on a business trip from New Zea-
land, where he had for some years been
building modern dredges on the Clutha,
and seeing the great possibilities OF the
business in California he went into 1t mere
and built a dredge on the Yuba River,
which began operating eighteen months
ago. This was the first here of the type
used in New Zealand-the continuous or
chain bucket type, in which an endless
chain of buckets is directed against bed
or bank. The scoop and clam smell dredSes
have paid under favorable conditions, the
suction dredge, so efficient for some pur-
poses. has always failed in this field, and
the New Zealand type has generally been
adopted though the first cost is larger.
When the Postlewaite dredge was in
stalled several large dredging plants had
been put into successful operation at va
rious places along the Missouri, in Mon
tana In Colorado and elsewhere through
the western region, where they are now
rapidly multiplying and interesting capl-
The success of the Postlewaite dredge
on the Yuba has been followed by the
building of five more making six great
dredges of the modern type One is on
the Trinity, one on the American. one on
the Yuba and three are on the Feather
below Oroville few miles. These dredges
are all similar. There are two pontoons
about 100 feet long connected so as TO
practically form one boat of that length,
% feet wide, with a we'll hole five feet
wide and 70 feet long, through which is
operated the ladder or girder, UP and
down which the chain of buckets travels.
This girder will, with its buckets. reach
ground 10 feet below water or quite dis
tance above Thirty eight heavy, steel
Tipped buckets or scoops travel at the rate
of fifteen per minute, driven by a 45-horse-
afral-
boulders of a ton weight, will dig into
hard ground and will scrape and dig up
the top of the bedrock. At the top the
buckets empty their material, which goes
into big revolving screen or grizzly sup
piled with 5000 gallons of water per min
ute. The fine material is washed through
the screen and passes to plates and TO
sluices fitted with cocoa mating and riff
fes where 98 per cent of the gold is said
to be saved. The tailings and the boulders
from the grizzly go to an endless carrier,
which reaches out behind and which will
stack the debris % feet high. The ma
chinery is massive to stand the shocks
and wear. One of these dredges is quite
a complicated and striking affair. Each
has a dynamo driven by a separate en-
gine for electric lights. and five-barrel
steam winch for the cables which radiate
from the corners and straight ahead to
hold the dredge in place and to move it.
Such a dredge costs $4,000. and in favor
able ground will handle 2500 cubic yards
per twentY-four hours. In Montana and
! Colorado such dredging plants have in
| cases been put on wheels running on
track. but wherever water can be had
floating is preferred. These dredges are
operated twenty-four hours a day by
three shifts of only two men each. The
only other necessary employees are one
dredge master and a general superintend-
ent.
Some of these dredges have been
Launched like any boat. but others have
not The one on the Trinity was built
nine months ago., and is owned by
Messrs. Gilman and McNeill of Chicago
who bought nearly four miles of placer
ground about Lowden's ranch. ten miles
above Weaverville, The dredger was put
the river on an old bar, and a slIiice was
started up stream to supply water to
float and operate the dredge The
dredge floated off and went to work at the
gravel about it. There is a great area
of pay gravel twenty-five to thirty feet
deep, enough to keep several dredgers
busy many years.