The St. Charles herald., 1922-09-09
instrument Developed During
word War Has deem Per.
fected by Engineers.
EXPERIMENTS PROVE VALUE
Vsssets Suoterransan Sounds AZ Great
o'ssanss-Aas Many Uses, but lts
advantage In Mine Rescue
Work Most Important.

washington.-As the result of ex.
Pefinents made by tho bureau of
mines, the geophone, a novel instru.
nient used amid the reek aud slaugh.
Ter or the World war for the detection
OF earth and rock sounds, made In
the construction Of military mines and
tunnels. promises to become I'm active
FACTOR in the saving Of the lives Of
miners entomhed as the result Of fires
and explosions.
In the course Of tests conducted In
the bureaus experimental coal mine
near Pittsburgh. blows with sledge
ON the coal face were heard. by means
OF the geophone. at a distance Of $50
feet. with various rooms and entries
intervening. On suspended pipe
line. light hammering with the knuck-
les was detected at a distance of
1.sOo feet. Ordinary talking and sing
ing could be detected through $50 feet
or solid coal. BY the use Of two geo.
phones, one instrument to each ear,
II Is possible to determine the direc-
tion from which sound Is coming
and thus to locate the approximate
position Of the entombed miner.
Another promising use Of the geo.
phone is in the location Of leaks in
water pipes. ByImeans Of the instru-
ment, It is possible to hear water cir
culating In TIE pipes of ordinary city
mains situated ten to fifteen feet below
the surface. Tests conducted at a
bssy corner In the downtown district
Of Pittsburgh located leak In q water
main which the water company had
sought to detect for two weeks vainly.
Sensitive, but Simple.
The mine geophone is sensitive, yet
extremely simple and easily portable
The instrument was invented by the
French during the war to detect sap
ping and underground mining opera.
tions 1t was developed by the United
States engineers, and the instruments
now used by the bureau Of mines were
made according to plans drawn by
them, except for the introduction OF
different diaphragms. The geophont
is essentially small seismograph. al
II embodies the same principles as tnt
ponderous apparatus that records
earthquake tremors. 1t really consist!
OF 4 lead weight suspended betweer
two elastic diaphragms cutting across
Z small alright box. II the instru
ment is placed on the ground and an!
one Is pounding or digging In tn
vicinity, energy is transmitted 9
wave motion to the earth, and tn
earth waves shake the geOphone case
The geophone, therefore. transform
tho earth wave into an air wave
which is heard by the ear as SOUND
and at the same time magniies tn
vave so that the sound Is louder thai
n the ears were placed In direct col
tact with the earth.
The observations Of the bureau Q
mines Indicate that the geophon
should be quite useful In the loci
t,on Of mine fires. Usually q min
ore makes enough noise. either D
drawing air or by breaking on STAT
and coal. to be heard for consit
erable distance through the coal, an
even through the strata above. Tn
a,s,ance that these sounds can
heard depends great deal on the nj
tnre Of the strata above the mine, y
the sounds originating at a mine NJ
.horld he detected through 100 to ~
seet Of cover and through 500 to ~
feet OF coal.
Aids Mine Engineering.
Geophones supply quick and fai
!. .ccurate method Of mine SURVEYING
r two tunnels are being brought Z
-s,ber from any direction, Il
progress Of the tunnels couic oe o