The patriot. (Glenmora, La.) 1918-1955, 1919-11-14


operations. The principle of the microphone was
applied in ascertaining in general way the loca-
ton of ship at sea- Toward the end OF the war
the device had been so perfected that 1t was pos
sble for the microphone listening station to cal
cuate the exact position of enemy guns after hear
ing the shots. The speed with which sound trav-
els, was Of course, known and served as basis
of calculations at different stations. With these
instruments electrically connected 1t was possible
to record the exact time at which the sound
reached them and them by series OF rather in
tricate calculations based on trianguation, to
locate the object.
The geophone is based on the same principle as
the mcrophone, excepting that sound waves are
recorded from the earth instead Of the air, and
1t has reached such high state OF development
under engineers of the bureau of mines that 1t
bids fair to be of the most useful applications
now being made Of inventions due to the war.
ceophone Is seismorraph.
The geophone though small Is essentially
seismograph, since ii works on the same principle
as the ponderous apparatus with which earth
quake tremors are recorded 1t consists of an
iron ring about three and half inches in diane
ter within the center OF which is suspended
lead disk that is fastened by single bolt through
two mica disks, one of which covers the top and
the other the bottom Of the ring There are two
brass pieces the top one having an opening In its
center to which is fastened rubber tube leading
TO stethoscopic earpiece These cap pieces are
fastened with bolts to the iron ring and serve also
to hold the mica disks in place.
We then have really nothing but lead weight
SUSPENDED between two mica disks cutting across
small alright box. II the instrument Is placed
on the ground and anyone is pounding or digging
In the vicinity, energy is transmitted as wave
motion to the earth, and the earth-waves shake
fine geophone case. The lead, on account of Its
.lo1h ofx. Tla
mica disks, remains comparatively motionless.
There then Is produced a relative motion between
the Instruments case and the lead weight. The
result Is that compression. and rarefaction OF
the Air ia the instrument takes place. Since the
rubber tube leading to the stethoscopic earpiece IS
connected with this space in the geophone. this
rarefaction and compression is carried to the ear
drum Usually two instruments are used, one for
each ear.
How Direction IL Determined
when the two instruments are used It has been
found that the sound is apparently louder from
the instrument nearer the source Of the sound.
+ Il evident then that by moving the instruments
nroperly 4 point can be found when the sound
WIN be of the same apparent intensity In both
oars The direction Of the sound Is then on q per-
von,iicular to the line connecting the centers Of
tha two instruments either In front Of or behind
The observer Further observation will show
which side Direction IL quite accurately de-
t.rirea III this way The sound Is not actually
loader n one ear than in the other, but the ear Is
81 distinguishing the difference ID time at
s,,ch the sound arrives In the two Instruments
,nce This is the case, persons who are slightly
deaf IN one ear are said still TO be able 70 De
term,ne direction with tie Instruments
r,nrlng the period Of the war engineers q the
mining division Of the bureau OF mines were
engaged il determining the distance tnat mler-
s,ss,g machines could be heard through the
,s,, ale coal and the mine cover Measure
,,sss we're made also Of the energy required ~
$3.50, sbaf they might be heard definite distances
ffraurl, clay. shaie and coal q vel e. g az