The Red Cloud chief. [volume] (Red Cloud, Webster Co., Neb.) 1873-1923, 1919-11-20

operations. The principle of the mcrophone was
applied In nscertaining in general way the loca-
lion OF n ship at sea. Toward the end of the war
The device had been perfected that It was pos
sible for the mcrophOne listening station to call
culnfe the exact position Of enemy guns after hear
ing the shots The speed with which sound trav
els. was. Of course, known and served basis
OF calculations ut different stations. With these
instruments electrically connected II was possible
70 record the exact time at which the sound
reached them and then by series OF rather In
tricate calculations based trlangulatiOn to
locate the object.
The geophOne Is based on the same principle rs
the microphone. excepting that sound waves are
recorded from the earth instead of the air, and
n has reached such a high state Of development
under engineers Of the bureau of mines that II
bids fnir to be one Of the most useful applications
now being made Of inventions due to the war.
Geophone Is seismosraph.
The geophone, though small, is essentially a
seislnogrnph. since it works on the same principle
ns 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 a
lead disk that is fastened by n 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 opening in Its
center to which Is fastened a rubber tube leading
10 a 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
u small alright box. If the instrument Is placed
on the ground and anyone Is pounding digging
IN the vicinity, energy Is transmitted as wave
motion 10 the earth, and the earth-waves shake
the geophone case. The lead on account of Its
weight and because It is suspended between the
mica disks, remains comparatively motonless
There q produCpd n motiOn hatx
the Instruments case and the lead weight. The
result Ia that n compression and rarefacton of
the air I'm the instrument takes place. Since the
rubber tube leading to the stethoscOpc earpiece is
connected with this space in the geophone, this
rarefacton and compression Is carried to the ear
drum. Usually two instruments used, one for
ench ear.
How Direction is Determined.
When the two instruments are used, 1t has been
found that the sound Is apparently louder from
the instrument nearer the source Of the sound.
II IL evident then that by moving the instruments
properly a point can be found when the sound
will be of the same apparent intensity In both
ears The direction OF the sound is then on per-
pendcular 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 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 still 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
snt 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
through clay. shale and coal. as well a. to de-