Sioux County pioneer. (Fort Yates, Sioux County, N.D.) 1914-1929, 1919-11-20

nand more accurate various mining
operations The principle of the microphone was
applied in ascertaining in general way the loca.
ton of ship at Toward the end Of the war
the device had been perfected that 1t was pos
sibe 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-
tels. was. of course known and served as basis
of calculations at different stations. With these
instruments electrically connected 1t was possible
ito record the exact time at which the sound
reached them and then. by series of rather in
4tricate calculations based on triangulation 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 az the most useful applications
now being made of inventions due to the war;
lSsaa &. eeophone % a seismograph. -
The geophone though small, is essentially q
seismograph, since 1t 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-i
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 two
bfass pieces, the top one having nm opening in its
center TO which'is fasenedsa rubber tube leading
fastened with bOltsto the iron ring and serve also
to hold the mica disks, in place.: q: H. ,.s
We then have really nothing but q lead weight
suspended between two mica disks cutting across
n small airtight 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 fine earth and the earth-waves shake
the geopllone case The lead, on account of its
weight and because 1t is suspended between the.
mica disks. remains comparatively. motionless.$
the Instruments case and the lead weight. The
result Is that compression and rarefacfon of
the air. In the instrument takes place. Since the
rubber tube leading to the stethoscopic earpiece Is
connected with this space in the geophons. this
rarefactlon and compression is carried to the ear
drum. usually two Instruments are used one for
each ear.
In How Direction 10 Determined. ~.
When the two instruments are used, It has been
foLnG that the sound is apparently louder from
tho Instrument nearer the source of the sound
It lie evident then that by moving the instruments
properly point can be found when the sound
will be of tile same apparent intensity In both
ears. The direction of the sound Is then on q per-
pendicuiar 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 one ear than in the other but the ear is
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 81 mines were
engaged to determining tie distance that differ.
ent mining machines could be heard through the
clay, shale. coal and the. mine cover. Measure
mentaswere, made also Of the energy required 10
order that they might oe heard definite distances
through clay. shale and coal. a. well % to de.