The Democratic advocate., 1884-06-07
Our 0liu.
Thunder and lightning.

The question of thunder storms, remarks
the Electrical ReUie,o, is an interesting
one, especially to telephonists and telegraph
lists. 1t is curious to see how one after
another of the old beliefs regarding thunder
storms are shown to be without foundation
in fact. The farmer will tell you that
thunder turns his milk sour because of the
sulphur in the air. But we know, now,
that there is no appreciable amount of sui
phur in the air during thunder storms and
that it is ozone. Prof. P. G. TAFT, of
Edinburg, who is an excellent authority
upon such phenomena, says that the me-
teorological effects of a thunder storm arise
from the extraordinary amount of vapor in
the air, and consequent immense fall of rain
and hail, He says that to find out the
amount of energy involved in changes of
that kind makes study of more than usual
interest. In considering it, the results
arrived at he looked upon as astounding.
Then he goes on to say:
''To evaporate a tenth of an inch of
water on square foot of ground required
a power equal to one horse for half an hour,
so that to condense one-tenth of an inch of
water on square mile they would require
one million horses working for the same
time. They had then no difficulty in un-
derstanding how it was that hurricanes and
typhoOns could be produced by the amount
of energy in the heat formed out of that
small quantity of water in condensing from
the vaporous into the liquid form" Going
on to speak Of the three forms of lightning
-forked, sheet, and globe--he said that
forked lightning was simply the same thing,
on an incomparably larger scale, as the
sparks they got from the electric machine;
and that the clash" was simply the air
rendered incandescent by resistance to the
passage of the electricity, in the same way
that the carbon in the Swan lamp was rem
dered incandescent by current of cleo
tricity being forced along it. A brilliant
flash of lightning lasted, it was computed,
only one millionth part of second Ex-
perimepts had been made which went to
show that bright object required to be
seen for one-tenth of second before its
real brightness was realized by the eye. If
it lasted only half that time, it produced
only half its brightness, and so on; conse-
quently flash of lightning was only seen
at hundred-thousandth part of its proper
brightness. If a flash of lightning lasted
the thousandth part of second, objects
would be as brilliantly Illuminated by it as.
they were in the sunlight; and if it lasted
one-tenth Of second it would have the
brilliancy of 100 suns, and would be blind
ing in its effects
Sheet lightning was merely the clouds
and vapor in the air lighted up by forked
flash, which itself was hidden from view.
And as to the curious phenomenon known
as globe lightning, they knew little about
it, as they had never been able to produce
it by experiments, and it had never been
observed by any trained observer.
The reason why such evident truths were
not heretofore discovered is, there is reason
to believe to be found in the theories which
up to comparatively recent period, were
entertained by those from whom we looked
to for explanation and investigation in this
direction. Professor TAFT, rejecting most
OF the old beliefs, studied out the problem
carefully and diligently, and his reasoning
is founded for the most part in much more
than theories, either ancient or modern.
referring to thunder, he shows how it
is caused by the sudden expansion of the
air on all sides of the lightning flash, fol-
lowed by an almost instantaneous thrush of
air when the flash has passed Thunder,
he says, was never heard more than fifteen
miles off from the flash of lightning; and
he remarked that the popular way of iudg-
ing the distance, of allowing a mile for
every five seconds interval between the
flash and the thunder was nearly correct.
The old notion that there was something
sulphurOus connected with the discharge of
electricity in the air had been discovered
to be incorrect. The sulphurous smell had
nothing whatever to do with sulphur but
with the great production of ozone, which
was merely modified form of oxygen. As
to the peculiar marks which lightning often
left on human body it had struck, the old
notion was that they were sort of photo
graph of some tree or object in the neigh
borhood which had attracted the lightning.
These were, however, caused by a disturb
ance in the nature of bruising of the small
capillary vessels under the skin. Dealing
next with the difficult question of the orr
gin OF electricity, Professor TAFT remarked
that the old idea that it was due to the
friction of the air was untenable. A French
investigator had suggested that every time
water containing salt in solution was evap-
GRATED the vapor which came off was always
charged with electricity That, said the
lecturer, was probably not far from true;
though it was not the whole. His own
idea at present was that electricity was