Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1919-04-22
VIZ ASHINGTON, D. c., April 7.--Wonder
wv full things are being accomplished
with that WAY devicn known as the

wv full things are being accomplished
with that war device known as the
GcOphOne, which was invented for locating
artillery fire, and is being applied by
the bureau of mines to variety of peaceful
purposes.
These purposes vary all the way from
locating knock in the cylinder of an engine
to locating a miner entombed in a mine
the result of an explosion.
One recent feat of the geOphone was per-
formed in connection with the digging of =
tunnel through a mountain. Two excava-
lions had been started from opposite direc-
tons, but they failed to meet because of
some mistake in the plans. The engineers
underground were unable to tell why they
had missed each other or by how much. They
faced the prospect Of tunneIing at random in
various directions until they met by acct
dent But the geophone solved the prob
lem by locating the end of each tunnel pre-
cisely from position on the ground above.
The great value of the geophone lies in this
fact that it not only hears sounds through
the earth, but locates the cause with surpris
ing accuracy. This mechanical ear thus &C
composites what the human ear is unable to
do.
Alan Leighton, assistant chemist of the
bureau, who now has charge of these inves-
LEGATIONS for the bureau, has given the fol-
lowing statement of general information re-
sarding the geOphone:
The instrument, though small is essential
ly a seismograph, since it works on the same
principle as the pOnderous apparatus with
which earthquake tremors are ded.
1t consists of an iron ring about three and
a half inches in diameter, within the center
Of which is suspended a lead disk, fastened
by single bolt through two mica disks, one
Of which covers the top and the other the bot
tom Of the ring. There then are two brass
cap pieces, the top one having an opening in
it's center to which is fastened a rubber tube,
leading to a stethoscopic ear-pieCe. These
cap pieces are fastened with bolts to the iron
ring and serve also to hold the mica disks
place.
We then have really nothing but lea.
weight suspended between two mica disks
across small air-tight box. If the instru-
ment is placed on the ground and any one
is pounding or digging in the vicinity, energy
IS transmitted as wave motion to the earth,
and the earthwaves shake the geophone case.
The lead weight, on account of it's mass, and
because it is suspended between the mica
plates, remains comparatively motiOnless.
There, then, is produced a relative motion
between the instrument case and the lead
weight. The result is that a disturbance of
the air in the instrument takes places Since
the rubber tube leading to the stethoscOpic
ear-piece is connected with this space in the
geoDhone, his disturbance is carried to the
ear drum.
Two instruments are used one for each ear,
and the sound is apparently louder from the
instrument nearer the source Of the sound.
1t is evident, then, that by moving the instru
ments properly, point can be found where
the sound will be of the same apparent in
tensity in both ears. The direction of the
sound is then a perpendicular to the line
connecting the centers of the two instruments
either in front of or behind the observer.
Further observation will show which side.
Direction is quite accurately determined in
this way.
During the period of the war, engil-~ IFS {
the mining division5 of the bureau of mines
were engaged in determining the distance
that different mining machines could be heard
through the clay, shale, coal and the mine
cover. Measurements were made also of the
energy required in blows that they be heard
definite distances through clay, shale and
COAL as we'll the distances at which the
shock waves resulting from the discharge of
various explosives could be heard. A brief