Vernon Parish Democrat. (Leesville, La.) 1917-193?, 1919-11-22

operations The principle of the microphOne was
applied in ascertaining in a general way the loca
ton of a ship at sea. Toward the end Of the war
the device had been so perfected that it was pos
sible for the microphone listening station to cal
culate 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 it possible
to record the exact time at which the sound
reached them and then, by a series Of rather In
tricate calculations based on triangulatiOn, to
locate the object
The geophone is based on the same principle as
the microphOne, excepting that sound waves
recorded from the earth instead of the air, and
it has reached such a high state of development
under engineers of the bureau of mines that it
bids fair to be one of the most useful applications
now being made of inventions due to the war.
eeOphOne Is seismograph
The geophone, though small, is essentially
seismOgraph since it works on the same principle
as the pOnderous apparatus with which earth
quake tremOrs are recorded. It consists of an
iron ring about three and half inches in dame
ter, within the center of which is suspended a
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 having an opening in it's
center to which is fastened a rubber tube leading
fastened with bolts to the iron ring and serve also
to hold the mica disks in place.
We then have really nothing but a lead weight
suspended between two mica disks cutting across
small air-tight box. If 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
the geOphone case. The lead, account of its
weight and because 1t is suspended between the
mica disks remains comparatively motionless.
There then is produced relative motion between
the Instruments case and the lead weight. The
result is that a compression and rarefactiOn of
the air in the instrument takes place Since the
rubber tube leading to the stethoscopic earpece 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 lie 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
It is evident then that by moving the instruments
properly a point can be found when the sound
win be of the same apparent intensity In both
ears. The direction of the sound is then on per-
pendicular to the line connecting the centers Of
the two instruments either in front Of behind
the observer Further observation will show
which side. Direction is quite accurately de-
termined in this way. The sound is not actually
louder in than in the other, but the ear is
capable of distinguishing the difference in time at
which the sound arrives in the two instruments.
Since this is the case, persons who are slightly
deaf in one ear are said stlll to be able to de
termine direction with the instruments
During the period Of the war, engineers Of the
mining division Of the bureau Of mines were
engaged in determining the distance that differ.
ent mining machines could be heard through the
clay, shale. coal and the mine cover. Measure
ments were made also Of the energy required in
order that they might be heard definite distances
Ahrnruh CLAW ahala and coal a. well az to de-