Evening star., 1914-02-08
Fire Balls and Thunderbolts.

From the Boston Transcript.
Organized observation, and a good deal
Of it. still leaves a great deal TO be ex-
planned concerning the character of lire
balls-which used to he called thunder
bolts-and meteor trains. The meteor
section of the British Astronomical As
sociation continues faithfully to report
instances of fire balls and of luminosity
accompanying and following the appear
ance of meteors or shooting stars in the
sky. -Four authenticated and recent in
stances are quoted by the Rev NJ. David
son in the current number of the asso-
cations journal The first was a fire ball
occurring at a calculated height of about
seventy-siX miles and disappearing at
height of forty miles; the second mete
or train in which the path of light lasted
for two seconds. the third fire ball with
trail lasting fourteen seconds and which
was apparently one OF the Perseid mete-
ors of August, and the fourth meteor
train lasting some seconds With regard
to fire balls We find ourselves in the diff
Guilty experienced by Mr.. De Morgan's
schoolboy who was asked to define a
rhomboid-''it all depends on what YOU
mean by a rhomboid' fire balls are
of two kinds. There are the fire balls
which have sometimes been credibly re-
ported by mariners, and which during
thunderstorms. actual or imminent, play
about the masts and rigging. These are
not discredted, but have been explained
as electrical phenomena such as can be
repeated by appropriate means in a Iabo-
ratory. Then there are the fire balls
which of old were called thunderboltS.
One was reported in the London Morning
Post nine years ago. when observers of a
thunderstorm at Bowers Clifford, Essex.
yt,af
vivid and explosive lightning discharge
they perceived "a cylinder. or "a ball of
fire. descend and explode. casting darts
in all directions The Rev. c. F. Box
added that next day they found in an
oatfield three distinct sets of circular
holes. ranging from nine inches in dame
ter downward, which were drilled as neat
ly as with an auger There vas no evi-
dence of A meteorite. the 'thunderbolt
may have been an illusion caused by ball
lightning. which Is an admitted phenome
non.
The other kind of fire ball still less
open TO dispute is that which accompa-
nies the appearance of meteors in the
sky and may also be partially an optical
Illusion, for. as w. +. Denning, the ref
cree for meteors. has found. human evi-
dence and human memory in these mat
ters is far from infallible. But that me-
teors can leave a trail of light is certain.
and the only matter of uncertainty is
how and why they do it. Prof. Trow-
bridge some years ago compared the
phosphorescence of meteor train to the
afterglow which follows certain forms
of electrical discharge in partial vacuum
tubes. This suggestion was revived and
elaborated at a recent meeting of the
British Astronomical Association. and
the presence OF ozone at low pressures
WAS suggested as an auxiliary. But. as
the Rev. NJ. Davidson points out, there
are a good many difficulties in the way
One is the state of th.nness of the gas
in which phosphorescence arises. 1t is
known that phosphorescence is best de-
veloped at certain pressures. These pres
sures correspond to heights between thir-
ty-stx and fifty-six miles Of the atmos-
phere But many meteor trails are OBJ
served at heights which are double this.
Again. a temperature of 300 degrees will
extinguish the glow in an exhausted tube
in the laboratory. and ii is certain that
the temperature of a falling meteor is
higher than that. Moreover hydrogen
cannot he made to glow. and most me
teor trails appear where we suppose the
atmosphere to be chiefly hydrogen. Evil
IDENTIFY either the theory is wrong or the
present beliefs Of the constitution of tn
upper air must be revised.