El Paso herald. (El Paso, Tex.) 1901-1931, 1919-04-25
GeObhOne Is 4
Nifty Little
Sound Carrier
Was Used In War, Is Being
Developed For Peace
Time Purposes.


Washington, Z. C.. April 25.-Woa-
derful things are being accomplished
with that war device known as the
geophone, which was invented for
locating artillery fire. and is now
being applied by the bureau Of mines
to a variety Of peaceful purposes.
These purposes vary all the way
from locating a knock in the cylinder
OF an engine to locating an entOmbe
miner as the result Of an explosion.
One recent feat Of the geophone
was performed in connection with the
digging OF tunnel through a noun
tain Two excavations had been
started from opposite directions, but
they failed 10 meet because OF some
mistake in the plans. The engineers
underground were unable TO tell why
they had missed each other o. by how
much They faced the prospect Of
tunneling at random in various di-
rections until they met by accident.
But the geophone solved the problem
by locating the end OF each tunnel
precisely from position on the
ground above
A Technical Ear.
The great value OF the Eeophone
lies in this fact that il not only hears
sounds through the earth. but To-
Gates the cause with surprising &C
curacy. This mechanical ear thus ac-
complishes what the human ear Is IN
able to do.
The instrument. though small, f.
essentially seismograph. since It
works on the same principle as the
ponderous apparatus with which
earthquake tremors are recorded
1t consists Of an iron ring about
three and a half inches in diameter,
within the center Of which is sus-
a
single bolt through two mica disks,
one Of which covers the top and the
other the bottom Of the ring. There
tnen are two brass cap pieces, the top
one having an opening in its center
70 which is fastened a rubber tube,
leading 10 stethoscopic ear piece
IneSe cap pieces are fastened with
bolts TO the iron ring and serve also
70 hold the mica disks in place
We then have really nothing but
lead weight suspended between two
mica disks across a small air-tignt
box II the instrument is placed on
the ground and any one is pounding
G. digging in the vicinity, energy is
transmitted as wave motion TO the
earth End the earth waves shake the
geophone case The lead weight, on
account Of its mass, and because Il
is suspended between the mica plates
remains paratively motionless
motion between the instrument case
and the lead weight The result Is
that a disturbance Of the air in the
instrument takes place. Since the
rubber tube leading 20 the stetho-
scopic ear piece is connected with
this space in the geoDhone, this dis
turbance is carried 70 the ear drum.
Determines Direction.
Two instruments are used. one for
each ear, and the sound is apparent
lv louder from the instrument nearer
the course Of the sound. 1t Is evil
dent, then. that by moving the in
struments properly. a point can be
found where the sound viii be Of the
same apparent intensity in both ears
The direction OF the sound is then on
a perpendicular TO the line connectinE
the centers Of the two Instruments
either in front OF or behind the OBJ
server Further observation wall
show which SIDE. Director is quite
accurately determined in this way
In tests IL was found that sounds
were transmitted only about half as
far in clay as in shale strata and
about one-quarter as far IN clay as ia
coal To give some idea OF the sem
sitiveness Of the instrument il may
be said that pounding with a pick
on the bituminous coal can be de-
tected for a distance Of 900 feet, AID
the direction determined, and that
pounding with a sledge can be heard
as far as 1850 feet
May save Lives
Now tha- the war IS over the
bureau work has turned to the de-
velopment Of the instrument for
peace time uses In this connection
IL is thought il may be Of great value
TO mine rescue crews entering mines
for exploration and 10 locate miners
entombed by a disaster The tests
so far made show that a man pound
ing on the coal rib with pick, piece
OF Z. Der, or a sledge can be detected
and located from a point 500 to 1900
feet distant
II is also thought that this de-
vice viii be Of value to prevent ac-
cidents from explosions IN this con-
nection an interesting incident hap
pened recently Observations were
being made at a tunnel heading The
pit boss happened along and asked TO
be allowed 70 listen. He put the ear