The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1884-05-21
Professor TAFT on Thunder Storm

In lecture on thunder storms, delivered
by Professor T. G. TAFT at Edinburgh, the
lecturer began by remarking that the mete-
geological effects of thunder storm were
the extraordinary amount of vapor in the cir
and the consequent immense fall of rain and
hail. He said that to find out the amount
of energy involved in changes of that kind
was an interesting question. In consider
ing it, the results they arrived at were as
founding. To eyaporate a tenth of an inch
of water on square foot of ground required
power equal to one horse for half an hour,
so that to condense one-tenth OF an inch of
water on a square mile, they would require
one million horses worked for the same
time. They had then no difficulty in IN
derstanding how it was that hurricanes and
typhoons could be produced by the amount
of energy in heat formed out of that small
quantity of water in condensing from the va
porous 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
incomparsbly larger scale, as the sparks they
got from an electrical machine; and that
the ''6ash'' was simply the air rendered IN
candescent by current of electricity being
forced along it. A brilliant fash of light
ming lasted, it was computed, only one-mil-
lionth part of a second. Experiments had
been made which went to show that a
bright object required to lie seen for ore
tenth of second before its full brightness
was realized by the eye. If it lasted only
half that time, it produced only half its
brightness, and so on; consequently fash
of lightning was only seen at hundred
thousandth part of its proper brightness. If
fash of lightning lasted the thousandth
part OF second, objects would be as brill
iantly illuminated by it as they were In the
sunlight; and if it lasted one-tenth of q Sec
suns, and would be binding in its effects.
Sheet lightning was merely the clouds and va
por in the air lighted up by forked fash,
which itself was hidden from view; and as to
the curious phenomenon known as globe
lightning, they knew little about it, as they
never had been able to produce it by expert
ments, and it had never been observed by
any trained observer. Speaking next of thun-
der, he showed how it was caused by the
sudden expansion of the air on all sides of
the lightning fash, followed by an almost in
had passed. Thunder, he said, was never
heard more than fifteen miles off from the
fash of lightning; and be remarked that the
popular way of judging the distance, of al
lowing mile for every five seconds inter-
val 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 sui
phurous 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 a
sort of photograph of some tree or object in
the neighberhood which had attracted the
lightning. These were, however, caused
by disturbance in the nature of bruising of
the small capillary vessels under the skin.
Dealing next with the difficult question of
the origin of electricity, Professor TAFT re-
marked that the old idea that it was due to
the friction of the air was untenable. A
French investigator had suggested that ev-
cry time water containing salt in solution
was evaporated, the Yapor which came off
was always charged with electricity. That,
said the lecturer, was probably not far from
true, though it was not the whole truth.
His own idea at present was that electricity
was caused by the friction of the water-va-
por particles against the air PARTICLES, be-
cause when two different bodies were in
contact they always gave off electricity.