Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1880-11-25
Thunder - Its Illustration Of Known
Properties of Sound.


Professor Tsit thus writes in Mature
We speak habtually and without eysg.
geratOn OF the crash OF thunder, the roll.
ing Of thunder, and OF a peal of thunder,
and various other terms will suggest them
selves as being aptly employed in differ.
ent cases. All Of these are easily explain
ca by known properties OF sound. The
origin OF the sound is, IN al cases, TO be
looked Tor IN the Instantaneous ana VIC.
I,nt dllatstlon Of the alr along the track
OF The lightning flash, partly, no doubt,
due 10 The descriptive effects of electricity,
out mainly due 10 the excessive Else of
mporature which renders the air for a
nom, III so brilliantly incsndescent There
IS thus an extremely sudden compression
OF the air oil round the rack of the spark,
and less sudden, but still rapid, rush OF
the air into the partial vacuum which II
produces, Thus the sound wave produced
must At first be OF the nature OF bore or
breaker, but as such stale of motion is
unstable, after proceeding moderate dis
lance the sound hlc> mes analogous 10
other loud but lets violent sounds such as
those OF the discharge of guns. Were
there few clouds, we're the air of nearly
uniform density, and the flash short one,
this would completely describe the phe.
nCmonon, and we shoaid have thunder
crash on thunder clap, according 10 the
greater or lese proximity of the seat Of
| discharge, Blu, Ms has long been well
known, not merely clouds but surfaces OF
separation OF masses OF sir OF different
density, such rs constantly q cur IN thuu-
Ger stems, II fleet vibrations in the air,
>nd thus we tnsy have many successive
echoes, prolunging the original sound
But there Is another cause, often more
tile .ent than these. When the fash lie
/ long one, all It's parts beng nearly tqui.
distant from the observer he heare toe
$ una from all those parts simultaneously;
/ but II lis parts be at very different dis.
tances from him, he hears successfully
/ the sounds from portions further distant
I rom him. Ii The fash be much ztg.
I Gagged, long portions OF lis course may
/ run at one and the same distance from
] MIN, ana the sounds from these arrive
simu ltaneousiy NJ his ear, Thus we have
40 difficulty IN accounting for the rolling
and pealing of thunder. 1t is, IN fact,
mer, const qucnce, sometimes. OF The finite
/ velocity with VIII Oh It is pfopagaled. The
usual rough estimate OF five secohds to
mile is near enough 90 the ruth Tor all
Culinary tblIuldtlNuf hl Nlc uleNahAc VI u
1 flash from the observer
/ The extreme distance at which thunder
/ rs heard is not great, when We consider
! The frequent great intensity OF the sound.
4 No Trustworthy observation gives Ia gen.
/ tral more Than about nine OF ten miles,
though there are cases IN which IT is pos,
/ sialc that IL may have been head four.
teen miles of Bat The discharge of
I slDgle cannon rs oiten heard at tilty milea,
Z and the noise Of siege or naval engage
/ ment has certainly been beard At dia-
/ lance OF much more than 100 miles.
There are two reasons for this: The first
depends upon tie extreme suddenntes Of
The production OF thunc er, the second,
and perhaps the most ti.Ctiye, on the ex.
CessivC variations Of density Ia he atmos
pbcre, which are invariably associated
with Il thunderstorm La certain cases
thunder has been prop6gated, for m0oe-
rate distances ir0m It's apparent source,
with velocity lar exceeding that | or
binary sounds. This used 10 be attributed
to the extreme audiences of It's produc
tion; bal II "a not easy, II we adopt this
hypothesis, 10 sec why II should not
occur in all cases Sir w Thompson
has supplied very different explanation.
which requires no unusual velocity OF
sound tecause 1t sssers the production
Of the sound simultaneously NJ all parts
of The air between the ground and the
cloud from which the lightning Is dis
charged.