Wessington Springs herald. (Wessington Springs, Aurora County, Dakota [S.D.]) 1883-1891, 1888-02-17
Some Strange and Interesting
Facts in Natural Phi
losophy.
how MUSIC EFFECTS A BRIDGE.
The Little Man Conscience Will Always
Tell Us the Right Thing
to Do.
Cuy,ositics of Sound and Filtration.

One person walking over q bridge,
stepping slowly, does no injury, be-
cause after each step the bridge recov-
ers before another step is taken; but
when large number of people step in
time to music, we have combined mo-
ton, and the bridge has not time to re-
cover between the steps. Hence dur
ing the passage of. troops and all we'll
regulated professions over bridge,
the music is stopped and the ranks
broken, so that the weight of the crowd
is evenly distributed, while some are
putting their feet down others are lift
ing theirs up. Sometimes fearful ac-
cidents have followed when this break
ing of step has not been observed.
Once in France a very long bridge went
down under a tody of soldiers march
ing over in ranks, resulting in the death
ofnearly hundred persons. There is
far less danger when a bridge is crowded
with people or cattle, or even many
heavily laden cars, than when few
persons are walking over keeping step.
The combination Of force is so great
and vibrations would increase to that
extent that a small dog could ruin the
finest and largest bridge if he could
trot back and forth, continually keep
ing exact time.
If we stand near piano and produce
musical tone with the voice, it will be
noticed that one particular string will
select that sound and respond to it.
Open the mouth wider. or make the
sound deeper in the chest or at higher
pitch, and the first string will cease,
while another string in the same key as
the voice will take up the strain. If a
hundred tuning-forks of different tones
are sounding at the foot of an organ
pipe, it will choose the one in accord
with it, and respond in that key alone
The sound called the song of the sea,
so often heard when shells are placed
close to the ear, is merely the vibrations
of the air within the she'll, and the two
shells placed with their bells near the
ear will increase the roar if the vibra-
ton of the air within is in unison or
sympathy. The same increase may be
seen with two tuning-forks; but if the
vibrations are different, the one will
counteract the other, like the process
sion marching out Of step, and no sound
will be heard perfectly. Other SUBJ
stances than air will convey the sound
waves; faint scratch on one end of a
long log may be distinctly heard ct the
other end, or q stroke on the end of a
long piece of tightly stretched metal
q bit of copper wire-will communicate
the shock to the other end many hun
dred feet away.
When bell rings, the tongue strik-
ing the side of the bell starts sound
wave that swells gradually until the ear
is reached, just as the little wave which
stone has disturbed increases in size
until it reaches the shore. If, when
the tongue strikes, the bell is touching
any other substance, discordant wave
is started which will destroy the one
before it, cutting it up, as it were, as
the small wave started at another point
from where We first threw the stone
will meet and "chop" the other, and a
calm ensues. A continuous blast Of air
produces no sound, any more than a
stationary stake in still water will pro.
duce waves, but let the pillows of air or
water strike an obstruction, and sound
or waves are seen.-Harpey''s Young
People.