Atlanta Georgian. [volume] (Atlanta, Ga.) 1912-1939, 1912-12-31
Travels on Heels of Light.

seconds to so mile.
Travels on Heels of Light.
Ire lightning bolt travels on the
heels Of the light, SO that H. too. s1
far outstrips the sound that if it
struck you, you would never hear
the thunder.
Even We. hoWever are able to
send death-dealing bolts faster
than the sound that accompanies
their discharge. \ swift rife bu-
let goes twice as fast as the crack
of the exploding cartridge.
Another useful fact to know is
that sound travels faster in water
than in air, in the proportion of al
least four feet to one. In some ex-
periments sound has been trans
mitted through the water of a river
at the rate of more than a mile per
second, but It's average velocity nI
water is about 400 feet per second.
The sound of bell warning a shin
to keep away from a dangerous
shOal would require about % sec
onds to go five miles through tho
air. while the same sound could Ice
transmitted through the water IN
about five and a half seconds
There are imaginable circumstances
i'm which the eighteen seconds thus
saved might suffice to prevent q
shipNreck.
Still more remarkable is the dif-
ference between the speed Of SOUND
in air and in solid bodies. In TT.
heavier metals, such as lead q.
gold. sound travels at nearly the
same velocity as in water but la
more elastic metals, like iron ar
steel, its speed suddenly increass
to more than three miles per sec
ond, which is six or seven times IS
rapid as the flight of a bullet
In wood sound travels about as
fast as in iron, provided that the
direction in which its waves move
IS the same as that in which the
tibers Of the wood run, but if the
sound is transmitted across the
gram Of the wood its speed IS re-
duced to from a half to q quarter
OF what it is in the other direction
the amount Of change varying for
different species Of wood.
Waves of Sound Differ.
You can hear the sound Of
scratching on wooden fence at an
astonishing distance. if your ear
lannon's f, 1a al, A.
if your head touches the fence And
so quickly is the sound conducted
that although its point of origin
may be quarter of a mile away.
yet if you are unaware of the
manner in which it has been
brought TO your ear, you may be
completely deceived, thinking that
Il must have originated but a few
rods Off one might easily make
kind OF telegraph of wooden
renee. conveying messages by taps
upon it. This suggestion is deaf
Gated TO writer's of ingenious stC-
ries of adventure.
How long are the waves Of sound
in the air? They differ according
to the pitch.
The average male voice, in ordi-
nary conversation, produces waves
varying in length from eight to
twelve feet while those Of a wom-
ans voice are only from two %
four feet long Waves sixty or
seventy feet in length, vibrating at
the rate of sixteen times per sec
ond. produce very grave sound
which is scarcely perceptible by the
human ear. while waves only hail
an inch in length, vibrating be-
tween twenty and thirty thousand
times per second. produce a sound
so shrill that il, too, passes beyond
the range 90 our hearing, although
it may seem as hoarse as the roar
Of thunder to the hearing apparatus
of insects. All sounds. whether
grave or shiu travel forward al
the same rate