New-York tribune., 1901-12-29
ELECTRIC OWNING RODS.
APPARATUS THAT INDICATES COPPER,
IRON AND GOLD.
MAPPING OUT INVISIBLE VEINS OF METAL
FROM THE SURFACE OF THE EARTH.


Park suburb of Chicago, seems to have
worked out the idea more effectively than any
else.
| The principle employed is simple one The
working of the system depends on the fact that
metal will conduct electricity better than or
dinary dirt rock This is frequently illus
trated by the return currents OF trolley road
! If the route originally provided for them- 4
properly connected set of rails fails to serve
satisfactorily, the electricity viii leak away into
/ the earth and take the shortest possible course
10 reach the gas and water pipes there
/ Nothing at all novel in the way IF instruments
! is required in this work 1t is necessary only
to supply small portable battery, 4 device like
a galvanometer- for measuring the resistance
offered to the flow of the current, and two wires
terminating in pointed metal rods which
be thrust into the ground These are inserted
into the earth. with interval of several hum
dred fe t between them, and the resistance care
fully observed and recorded. The positions may
be marked with surveyors stakes, for sub
sequeut reference. then both metal rods are
pulled up. carried along in the same general
direction-say to the southward-and again
thrust into the SOIL the distance between them
being the same before After number OF
repetitons of this performance it may be dis
covered that the recorded readings show con-
siderable differences II so. the lowest VIII
At the outset the operator may have idea
/ either of the existence of the vein the drec-
tion in which it The former having been
! revealed. the latter is next investigated One
terminal is inserted at a spot giving low read
ing and the other. carried about in the hand.
is swung and fro slowly, while sharp watch
of the measuring instrument is kept When
minimum OF resistance is observed, the free ter
minal is stuck into the earth. and the same
| tactics pursued with the other 1t is
serted that the metal rods finally found TO
be standing directly above the vein And with
proper it is possible 20 map out irreSu-
laritics and ramificatons well as the prn-
! ciaal deposit
Two trials of this apparatus are mentioned by
''Thc Western Elcctrician' one in Mon
| tana On either side of the metallic streak the
| resistance $1,000 Ohms. Immediately over
/ "A rich vein Of copper il dropped JG ohms-
The other test in Michigan. in a place
where the percentage of native copper in the
rock only from 2le TO 81. per cent Here
the resistance of the adjacent soil was 1900
10000 ohms, while over the vein it dropped
10 900. The latter exploration was conducted
in a crude and imperfect fashion. Had it been
i carried further, perhaps the readings would
have fallen to 200 or 300.
Dampness in the earth improves its
ductivity but not to so great an extent
figures obtained with the electric divnng rUd,
but the expert cannot be deceived. He learns
in time to recognize other Influences which affect
the readings and to distinguish between them
and the object in view. Copper and iron, OF
course have the highest electrical conduCtivity,
and consequently show very low resist ance. But
it is possible to find gold, also. by the method
here described.
Some notion of the depths at which a metallic
DEPOSIT lies may he derived from the interval
between the two terminals at which the best
did not come within 2OO feet of the surface, and
the two pointed rods placed only 80 feet
apart, the current might traveY almost straight
from to the other, at depth of only few
feet. 1t would encounter less resistance in doing
50 than in diving 100 feet. traversing the copper
for 30 more, and then coming up again. Con-
scquently the rods planted that the dis
tance between them is twice great that
which the metal is supposed to be from the
surface.
The inventor has succeeded in interesting n
. this apparatus James j. Hill, president of the
Great Northern Railway Mr.. Oliver. the head
, of the Oliver Iron and Steel Company, and a
number of other men prominently identified
with the mineral interests of the Northwest.
They will put it to i'll locating unknown
deposits in that part of the country