Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1918-08-09
Bx GARRETT p. sERvIss

Hy GARRETT Il. SERNlsS
I'm a letter from my sister In
iceland she tells me that during, a
neavy snowfall last winter wooden
stick with an iron point that she
had in her hand had a light on top
ike a candle. | have heard that IN
similar circumstances people some
lines see lights on their tinger tips.
While, | am convinced that TINS
caused by electricity in the air, l d9
aot understand why the light seems
20 burn steady instead of appearing
as a spark. as with lightning.
should also like to know how hlgh
voltage is generated in the clouds
when lightning occurs, and II 1t IS
generated by movements Of the CLOUDS
through the magnetic field OF the
sarth-E. J. ". Cicero, Ill.
The phenomenon seen by your sis,
ter in Iceland was st; Elmo's FIRE,
contracted form Of corpo santo. mean
ing holy body'D, about which many
superstitions and legends have been
woven. and which has served as
picturesque element in scores OF sea
tales.
1t is an example of the brush cleo
.ric discharge, which takes place. ac-
,ording to circumstances, either in the
form of a sheaf of minute rays OF
light, attended by a kissing or crack
ing sound. or of steady. silent glow.
The latter occurs when the object
hat serves as the focus has a point
I'd shape.
The explanation of the whole phe-
nomenon is based on the fact that
the electricity passes so readily that
a charge, or difference of potential,
sufficient to cause spark cannot ac-
,umulate.
With an electrical machine the
lights may be caused to appear in
both their characteristic forms, and
either on the conductor of the ma
;,hine. or on an o6ject, presented pres tea
conductor a discharge is passing.
Tufts of light will form on the tips
of the fingers when presented to a
er of getting a shock through the
sudden formation of a spark.
When the lights appear in the open
air. 5 they were seen by your Sis
ter the discharge takes place from
clouds. or other aerial accumulations
close at hand, the objects tipped by
The plow serving, like lightning rods,
to draw off the electricity so rapidly
disruptive point. If it did a shock
equivalent to a lightning stroke
might be received.
When the electric accumulation is
formed very rapidly, however, the
difference of potential. or voltage,
may become so great that no steady
high, and then a discharge of great
1iolence will occur, like the bursting
Of dam by the water of cloud
ourst.
a
may amount to millions of volts.
Lord Kelvin showed that the differ
ence of potential per cenumeter re-
luired to produce a spark in air mas
trostatic units, equivalent to $4,000
volts. To produce a spark a mile
long, and lightning sometimes reaches
several miles would require a poten-
tial of more than 6,OOO,OOO 900 volts.
This, great potential, as, P. g.
Tait showed is accumulated by the
aggregation together of millions of
minute particles each carrying,
small charge. and forming when
united a drop of water, whose cleo
trio potential may be measured by the
vided by the cube root of that num-
Thus. if 100000 spherical parti-
cles, each carrying an equal charge,
radius of the drop will be represent
ed by 100, while the quantity of
electricity carried by it will be repre-
will be 1000. 900 divided by 100 or TO-
600 times as great as was the po-
tential of each of the particles before
Combina tion.
st. Elmo's Fire may be regarded as
kind of tame lightning. 1t is
lightning in a diluted form or light
ming too powerless to strike. History
astonished the most level-headed OBJ
servers. julius Caesar once saw the
points of the iavelins of his NTH
legion tipped with fire on stormy
night in Gaul. Pliny, the Roman
naturalist, was much interested in
what we call St Elmo's Fire. but
which the Roman sailors named for
Castor and PolluX when a pair of the
lights appeared among the rigging
of the ship, while if only one light
was seen they called it Helen. after
the unfortunate heroine of the siege
of Troy. and considered It to be a
bad omen. Two lights. however, were
regarded as lucky
Occasionally a large number of the
lights appear simultaneously, tipping
the mast-heads and the ends of the
spars with mysteriously looking
flames which sometimes wander
about. appearing suddenly in a new
place in manner startling even to
experienced observers. On land SIM
Thus there is a story of load of
straw driven under a black cloud
which suddenly appeared to be in
flames, every straw giving forth a
streak of light while even the driv-
flame"
During a thunderstorm a whole
forest has been seen to become mo-
mentarily luminous just before each
lightning flash. On the Alps and
other mountains it is no very uncom-
mon phenomenon to see electric
flames poised on the heads of alpen-
stocks or PLAYING about the heads
and hands of climbers. Thus does
electricity proclaim it's universally
ana pique us with it's enigmas.