The Logan County banner. [volume] (Logan, W. Va.) 1889-1903, 1890-01-30
SOMETHING ABOUT SOUND.

An Entertaining Talk to the Children
Upon an Interesting Subject.
We have such an interesting subject
to think about to-day, children. Sound.
1t is such wonderful traveller, goes all
over the world and travels faster than
lightning express trains could carry any
Of us. Sound doesn't travel as fast as
light though, for light could go 43o
times around the earth while sound was
going It's thirteen miles, for sound trav-
els thirteen miles minute. However,
we have nothing to do with light to-day,
and had better begin to find out how
sound Is produced. You have often
stood on the shore Of lake or pond and
thrown in a stone, just to see the little
circles of waves it produced, haven't
-yon2r Now when you strike some hard,
elastic substance, like iron, copper, bell
metal or glass, you set in motion waves
of air Just as you produced the waves in
the water, only you can not see them.
When these waves strike against the
drum of the ear it produces sensation
which we call sound. But You say some
times we can't hear sounds distinctly,
well it Is because something interferes
to break the little sound-wave before 1t
reaches you're ear, just as though your
little wavelet in the lake broke upon a
rock before it reached the shore. There
are many and different ways in which
the sound waves are broken, sometimes
the falling rain breaks them up, and the
snow falling will stop their progress.
Then the sun in the daytime, heats the
air and produces strong currents and
breezes, SO that the air is not always
uniform For this last reason we hear
sounds more distinctly at night, when
the whirl of business ceases and leaves
the air still When air becomes rare
fed that means thin, not dense) sound
becomes less intense, fainter. know
this to be fact because II you ring a
bell in the receiver Of an air-pump and
then begin to exhaust the air, the sound
will keep growing fainter until the air
is all exhausted. That is the reason.
children, that mountains are so silent
and quiet, because the air OF mountains
is very rare or thin, and as the air be-
comes rarefied, sound diminishes.
1t is in this way that God has wrapped
tains, setting them apart from the noise
and hustle Of the world, and just here
let me leave a thought with you. Have
you noticed how often Christ went apart
from the others on the mountains to
pray, and how he chose mountain for
His temple when He preached that won
derful sermon Of the bcatitudes? But
now we come to another phase Of sound
IAN echo. When one of these sound
waves strikes against an obstacle, like
a hill or wall, it is thrown back or re-
Elected, just as when light Is thrown
against bright surface it is reflected
or thrown back. When this happens
with sound it is called an echo. The
most famous places for echos are grot-
toes, old Abbeys, caverns and cathedral
aisles, because the sound-wave can not
pass beyond the walls and must be
thrown back. Sometimes these return
ing sound-waves become entangled in
turnings and windings Of the cavern,
4 and come back very deliberately. The
farther of the echoing body is the more
sound is reflected. Sometimes an echo
will repeat two syllables, because the
echoing body is so far of that there is
time for one reflection to pass before an
other reaches you. Then, sometimes 1t
happens that there are two or more
separate surfaces that the sound-wave
strikes and reflects in succession. II
you ever so to Scotland, children, ask
your courier to take you to place call
ed Rosmeath, seventeen miles above
Glasgow, for there is a very remarkable
echo there. IF trumpet plays tune
and stops, the echo will begin the same
tune and repeat it accurately; as soon as
this echo has ceased another will echo
the same tune in lower tone, after the
second echo has ceased third will sue
coed with equal fidelity though in a
lower tone"
At one place on the lakes Of Killarney
in Ireland, II the guide takes up his
pipe and plays any simple tune, the echo
will accompany him with an excellent
second. Christian at Work