The San Francisco call., 1905-04-22
MINERS OF SKILL
GIVE LIVE FACTS
Hohl Talks About Dredgers
Leggett Deals WIA Deep Mining the Rand and Tells
Ho0O Diamonds IRE Limited.

The annual publication by the Cali
tornia Miners Association Of essays
and other matter contributed to the
last convention Of the association by
experts, as corrected carefully by au
thors, supplies enough that is timely
10 be Of present and leading interest.
relative TO gold dredging in the Oro-
Nliie district some facts are supplied
by Il J. Hohl that are instructive and
equally entertaining in narration. De-
talling the methods adopted in dredg-
ing, Mr.. Hohl says succinctly:
There are no very reliable data o. large
enough scale TO deterznine the relative value
and ssterwsrd developed by the dredge. II
seems to be conceded that the percentage 70
which the Greoge Will work. provided the drill
holes are numerous enough. vary between 70
Per cent and 90 per cent l Will Try TO give
ne principal features OF q good gold dredging
second, good bedrock which can be cut into
and scrsped up by the digEing buckets; third,
Ester Ine: fourth Easy digging ground: nth.
sooo facilities for power; sixth, proximity 70
eighth, proper contour Of groundg ninth ac-
oessibilltyi tenth, reasonable first cost OF lano-
inAoeacec ey al the rest Of them. but prao-
tloally al these conditions were met with al
one tE1e n the Oroville district; az present
oslleaos Is no, % easy 70 snd and tn the limit Of
ersdEsble ares IN the district is being rapidly
be found and with the knowledge acquired in
ana near O-ovtlle dredging while sttN IN tne
experimental stage, is bound TO become sci
ence and take rank with older uaethods OF
mining that have been developed 70 hSh
Ersae OF perfection
So much valuable information con-
cerning gold dredging in the Oroville
district has never before been com
municated IN such small space.
A VIEW OF THE RAND.
vastly interesting series Of state
ments relating 10 the Rand mining
problems is contributed by Thomas
Haight Leggett and other facts OF
scarcely less interest regarding dia-
mond mining are presented. About the
Rand, Leggett says in part:
The question has naturally arisen as 70 what
depth mining would ultimately reach the
Rand This touches closely upon the matter
sb1lity. with the object Of endeavoring 10
form some IDEA OF how much gold there was
ia the known area Of these reefs I had the
er1ck II. Hatch. In the preparation OF an es-
tinlsse OF the gold production and life OF the
This does not mean that in our opinion the
Rand reefs would be worked everywhere 10
necessary set some limit. and II is evil
dent that the reefs could be worked out 10
shaft OF 5000 feet in depth. but by means OF
incline shafts at the bottom OF the verticals
from 45OO 70 5000 feet deep we felt II safe 10
estimate the gold contents 10 this limit There
IS no doubt in my mind that the miners
Of The Rand will feel their way 10 these great
er depths IN the future just as they have done
The profitable yield from the first row of
deep level mines encouraged the more strenu-
Gus development OF the second TOW. the mines
Of which are now reaching the producing stage;
and this ] take IL, will be the case with the
third and any successive row. Ny personal
opinion Is that beyond the third row OF deep
levels there viii be very few vertical shafts.
ground hv long iuclines from the bottoms OF
the shafts already projected and in course OF
sinking.
IN speaking Of the working capital neces--
propertte. the Rand. 1 an telling nothing
new when ] say that the mines In the first
TOW Of deep-levels have expended from two
end q hslf 10 three million dollars each for
development and equipment before getting
out single ounce OF gold. But with gold
deposit OF pebble-cong glomerete lying in seoi-
rnentsry strata. and proven By boreholes 70 a
depth o. 1850 feet, 70 say nothing OF the hun
comprehensive policy OF mine development has
shown itself 10 have been not only well found
ed but commercially successful At the same
time. like all policies. Il has Its limits and
deep-lexel area OF the Rand without inviting
disaster: hence my remark that the miners OF
the Rand viii undoubtedly feel their way
IN the exploitation OF the greater depths be-
fore undertaking too heavy expenditures in
deep shafts.
THE CTNCH ON DIAMONDS.
Purchasers OF diamonds will be en-
terteined by an instructive statement
made by Leggett relative TO methods