CHARACTER OF LIGHTNING AND OF THUNDERSTORMS.
It is well remarked by Arago, that although we know nothing about
lightning, beyond the well-ascertained fact that it is one of the
manifestations of the equally vast and mysterious electric forces
pervading the universe, we yet may ascertain a great deal about
its mode of action by continued observation, made by many persons
and at many places. As yet the wise recommendation of the French
astronomer has, unfortunately, not been acted upon to any extent,
or in any systematic manner; still, a good many facts and incidents
have been gathered which serve to throw a strong light upon the
apparently erratic, but in reality normal manner in which, as in
obedience to some grand unfathomable cosmic law, the fire of the
clouds flashes along its self-made path. That these observations
are entirely modern, detracts nothing from their value. With all
their famed civilisation, the classical nations of the ancient world
never came to look upon lightning and thunderstorms as regular
functions of nature, but regarded them with dread and horror. Even
the greatest of their natural philosophers found in them means only
for encouraging popular superstition. Thus Pliny the Elder, in his
celebrated ‘Natural History,’ recommends, like Arago, notes being
taken about thunderstorms, but for quite a different purpose. ‘Nothing
is more important,’ says the celebrated author of the _Historia
Naturalis_, than to observe from what region the lightnings proceed,
and towards what region they return. Their return to the eastern
quarter is a happy augury. When they come from the east, the prime
quarter of the Heavens, and likewise return thither, it is the
presage of supreme felicity.’ It is reported by travellers that this
form of superstition--which has reference, of course, to the zigzag
form of many strokes of lightning, apparently in turn advancing and
retrograding--still exists in some districts of Southern Italy.
The superstitious awe with which lightning was looked upon not only
in ancient times, but in which it is still held by the ignorant at
the present day, finds its easy explanation both in the nature of
the terrifying phenomenon, and in the fact that even now we can only
speculate upon some of the causes of its seemingly capricious actions.
There can be no doubt that thunderstorms will visit some districts
in preference to others, and that lightning will descend constantly
upon some selected spots, and will entirely keep away from others.
As regards the latter case, old historians were fond of quoting the
grand temple of Solomon at Jerusalem, which was never struck by
lightning in the course of a thousand years, although thunderstorms
burst unceasingly over the Holy City, creating immense havoc and
destruction. In this instance at least, the explanation is simple,
although it may not be so in many others. It is stated expressly in
the biblical description of the building of the world-famed temple (1
Kings vi. 21, 22) that ‘Solomon overlaid the house within with pure
gold; and he made a partition by the chains of gold before the oracle;
and he overlaid it with gold. And the whole house he overlaid with
gold, until he had finished all the house; also the whole altar that
was by the oracle he overlaid with gold.’ If wise King Solomon had
known Franklin’s discovery of the protection against lightning given by
metallic conductors, he could not have guarded his magnificent edifice
better than he did by having ‘the whole house overlaid with gold,’
as stated in the Bible. But he did even more than this, according
to the historian Josephus, who records that the roof of the Temple,
constructed in what is now called the Italian style, was ornamented
from end to end with sharply pointed and thickly gilded pieces of
iron, in lancet form. These points, the historian surmised, were
placed there to prevent the birds from settling on the magnificent
roof, and soiling it, and it is very possible that this was the
original design. Nevertheless, it is certain that King Solomon guarded,
although, probably, without intending to do so, his magnificent temple
as perfectly against lightning, as could have been accomplished by
the best arranged system of conductors. It is not often that many
thousands of pounds are spent for protection against lightning, even
if intended for great cathedrals and splendid royal palaces; but King
Solomon disbursed, by the most trustworthy calculations, no less than
thirty-eight millions sterling in covering the temple with one of the
best of conductors--including the pointed and gilded lancets along the
roof, as perfect ‘Franklin rods’ as were ever designed by any architect.
If it is easy to account for the old historical marvel of Solomon’s
temple having stood unharmed amidst the ragings of lightning from
tens of thousands of storms, it is more difficult to find the reason
why many buildings of another kind should be constantly under attack.
A notable case in point, related by the German naturalist G. Ch.
Lichtenberg, occurred at the village of Rosenberg, in the province
of Carinthia, Austria, belonging to the noble family of Orsini. The
village church, although not standing in a very elevated position, was
unceasingly struck, in the course of the seventeenth and eighteenth
centuries, by lightning, which sometimes battered in the roof,
sometimes broke down part of the steeple, and often flew in at the
window on one side and out on the other. Very possibly, there were
large pieces of metal on the wall, or in the roof; or, if not, there
may have been masses of water near, underground, sufficient to account
for the manifestations of the electric force. However, popular opinion,
utterly ignorant as to such causes, ascribed the whole to the doings
of evil spirits, and endless attempts were made to exorcise them
by prayers, fastings, and sprinkling of holy water. But it was all
unavailing. The lightning came again and again, and in the summer of
1730, a flash from the clouds, more violent than any preceding one,
demolished the entire steeple. The Orsini family, suspected by many of
the lower people of being the secret originators of all the mischief,
in league with the evil spirits, erected another steeple, handsomer and
far more solid than the one destroyed, to show their pious intentions.
But the lightning visited it as before, on the average five or six
times a year, doing so much damage that the whole church had to be
taken down in 1778, being found in ruins. Happily, in the meanwhile
the report had gone as far as the little village in Carinthia that
something had been discovered for guarding all buildings, including
spirit-haunted churches, against damage by lightning. Once more, the
proprietors of the village built a new church on the old ground, but
this time, by the advice of an Italian architect, they placed upon it
one of the ‘heretical rods,’ made famous for having done good service
in protecting the cathedral of Siena. Needless to say that it did again
similar service.
It is very probable that, besides the two causes just referred to which
divert the path of lightning, there are many others of influence,
at present entirely unknown. Numerous cases are reported where the
electric discharge from the clouds touched precisely, and with
singular accuracy, as if directed by a superior intelligence, the
same spot, without the slightest reason being discoverable for such
an action, after the most minute investigation by competent persons.
Thus, on June 29, 1763, a violent thunderstorm broke over the village
of Antrasme, near Laval, in France, the residence of a distinguished
investigator of electrical phenomena, Count de Labour-Landry, a friend
and correspondent of the Abbé Nollet as well as of Benjamin Franklin.
The lightning struck, as carefully ascertained by the Count, first
the steeple of the church, then sprang to one of the lower walls,
where it fused and blackened the gilding of picture frames and some
other metallic ornaments, melting also some pewter flasks used for
sacramental purposes, and finally opened two deep holes, as regular
as if they had been drilled with an auger, in a wooden table, placed
within a recess of soft stone. All these damages were duly repaired;
but, to the boundless surprise of the witnesses, the lightning struck
the church almost exactly a year after, on June 20, 1764, entering
the church by the same way as before, fusing and blackening the same
gildings, melting the same flasks, and, in the end, driving out the
very plugs of the wooden table inserted to fill the holes bored by
the previous stroke of lightning. The account of the whole might seem
almost incredible, were it not attested by independent eye-witnesses.
Arago, with absolute faith in their testimony, remarks thereon that
‘those who will take the trouble of reflecting upon the thousands of
combinations which might have caused the path of the lightning to have
been different in the two cases, will, I imagine, have no hesitation
in viewing, with me, the perfect identity of effect as demonstrating
the truth of a proposition I put forward,’ namely, that ‘lightning, in
its rapid march, is influenced by causes, or actions, dependent on the
terrestrial bodies near which it explodes.’ In other words, lightning,
like many other phenomena of earth, air, and water, is influenced by
unknown causes. Hamlet says very much the same, when exclaiming:
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
After all possible explanations, Arago could get no further than
Horatio, who thought that there was much in the universe which was
‘wondrous strange.’
It does not seem impossible that some of the extraordinary effects
of lightning, either in striking repeatedly certain objects, or in
seldom or never touching others, may be explained on meteorological
grounds. The height, as well as thickness, of the clouds charged with
the electric fire, must naturally greatly influence the direction of
the latter, and though both elements vary enormously, in different
countries and at different seasons, it is likely enough that the
variation is comparatively trifling under given conditions, as, for
example, in a district where there are prevailing winds, and where the
configuration of the earth powerfully acts upon the drift and movement
of the aerial masses, and the atmospheric conditions in general. As
to the height of the clouds charged with lightning, there appears
scarcely any limit, as it has been found that they at times rise above
the summit of the most elevated mountain ridges on the face of the
globe. The great naturalist and traveller, Alexander von Humboldt,
measured the height of a storm cloud, discharging lightning, near the
mountain of Toluca, in Mexico, and found that it was no less than
4,620 metres, or 15,153 English feet, above the level of the sea. The
height of another, ascertained by Professor de Saussure, of Geneva,
when ascending Mont Blanc, was 4,810 metres, or 15,776 English feet,
or almost exactly three miles. Probably, these are exceptional cases,
as even in mountainous districts the heavy moist and electricity-laden
clouds seldom rise to such extraordinary heights; still, even such
as they are they do not represent the extreme limit of elevation. A
member of the French Academy of Sciences, M. De Lisle, records having
measured, by trigonometrical observations, the vertical height of
clouds in a thunderstorm, with strong flashes of lightning, which broke
over Paris, and found it to be 8,080 metres, or 26,502 English feet.
Consequently, this cloud-mass, charged with electricity, stood far
above the summit of the highest mountain peak in the world.
If some of the lightning-clouds tower at a gigantic elevation over the
earth’s surface, there are others that lie almost flat on it. There are
some remarkable observations on this kind in existence, made by German
meteorologists. Two of these deserve particular notice. On August 27,
a heavy storm burst over the town of Admont, on the river Ens, in
Styria, and the lightning, falling upon the lower part of the great
convent of the Benedictines, and passing through the wall, killed two
young priests near the altar, while reading vespers. The convent lies,
like the town of Admont, in a valley, and above it, some three hundred
feet higher, stands a castle, in which resided at the time a German
professor, specially interested in the phenomena of thunderstorms. He
watched assiduously the coming storm, and saw the lightning fall upon
the great convent, noticing all the while that the gilded cross placed
on the belfry of the edifice, about 115 feet from the ground, remained
standing out clear above the electric cloud, which appeared to come
close to the earth’s surface. He noticed further that above this cloud,
enveloping the ground portion of the Benedictine convent, there hovered
another, more than two thousand feet higher, and at intervals he could
see streaks of lightning fly from between the two, not however from the
more elevated to the lower one, but in a contrary direction. It was
evident that the two clouds must have been charged by electric forces
of different ‘degree,’ or ‘potential;’ it may be, one of a ‘negative’
and the other of a ‘positive’ kind, or, as Benjamin Franklin termed
them, ‘plus’ and ‘minus;’ although, as long as the forces differ in
‘degree’ or ‘potential,’ it is not essential that they be of opposite
kinds. As the marvellously sagacious discoverer of the lightning
conductor surmised, the wondrous force is really unitarian--that is,
throughout the same, the term ‘kind’ really only indicating on which
side of an assumed zero (the potential of the earth) the observations
or measurements are made.
Another notable instance of low-lying storm-clouds, and which furnished
the rare opportunity of measuring the thickness of one of them,
occurred at the city of Gratz, Austria, on June 15, 1826. The city is
built along the side of a hill, the highest point of which, called the
Schlossberg, has on its summit a castle, now in ruins, but at the time
garrisoned by troops, and furnished with a small observatory. When
the storm in question broke over the city, several scientific men on
the Schlossberg took notes of the movement and direction of the great
cloud emitting its electric discharges. This they could easily do, as
they themselves, on their altitude, were standing in sunshine, under
a perfectly blue sky, the dark cloud-wave rolling deep under their
feet, indicating its path and size by streams of fire, following each
other in rapid succession. Exclusive of short flashes, vanishing in
the air as soon as seen, there fell nine great strokes of lightning
upon buildings in the city, in the course of about three quarters of
an hour, five of them causing conflagrations and killing a number of
people. The storm over, the observers compared their measurements, and
it was then found that the height of the storm cloud had never been
above the clock-tower of the Johanneum, an edifice connected with the
university, and containing a library and museum, while the lowest part
of it had gone down the sloping ground of the city no further than 120
feet under the summit of the clock-tower. This, then, was the exact
thickness of the storm-cloud which had caused so much destruction.
It was noticed on this occasion, as had been done often before, that
the discharges of lightning fell all upon buildings standing on moist
ground, near the river Mur, a mountain stream coming from the Noric
Alps, and dividing the city into two parts. There can be no doubt, from
thousands of observations made, that it is one of the characteristics
of the electric force to seek its way towards water--to be, as it were,
dissolved by it, or, as perhaps it might be said more truly, to be
equalised by it. A very remarkable electrical phenomenon, and one which
is often attended with fatal results to men and animals, is what is
known as the ‘return stroke’ of a lightning discharge. This is always
less violent than the direct stroke, but is nevertheless very powerful.
It is caused by the inductive action which a thunder-cloud exerts
on bodies placed within the sphere of its activity, and disastrous
effects often take place upon objects, upon men and animals on the
earth under the cloud, although perhaps miles away from the point
where the discharge takes place. These bodies are, like the ground,
charged with the opposite electricity to that of the cloud; but when
the latter is discharged by the recombination of its electricity with
that of the ground, the induction ceases, and all the bodies charged by
induction return to a neutral condition. The suddenness of this return
constitutes the dangerous ‘return stroke.’
Lord Mahon was the first to demonstrate by experiment its mode of
action; as shown in the following illustration.
[Illustration]
A B C is the electrified cloud, the two ends of which come near the
earth. The lightning discharge occurs at C. A man at F is killed by the
return stroke, while those at D, nearer to the place of discharge, but
further from the cloud, receive no injury. It may be mentioned that it
was the action of the return shock upon the limbs of a dead frog in
Galvani’s laboratory that led to the Professor’s experiments on animal
electricity, and further to the discovery by Volta of that form of
electrical action which bears his name.
The subject of the origin of atmospheric electricity has at all times
been a favourite source of speculation with scientific investigators,
and given rise to numerous hypotheses. The eminent Swiss savant,
Professor de Saussure, already referred to, held that all atmospheric
electricity was due to the evaporation of the waters of the globe
through the effect of the sun. To prove this, he made a great number of
experiments, showing that whenever water, whether pure or containing
more or less salt, whether acid or alkaline, is projected upon a
metal crucible heated to redness, the evaporation that takes place
immediately is accompanied by strong liberation of electricity. The
fact is undisputed by scientific men, but not so the conclusion.
Another eminent savant, no less distinguished than De Saussure,
Professor De la Rive, in taking up the experiments of the former,
succeeded in showing that the production of atmospheric electricity
by throwing water upon heated metal was not the simple effect of
evaporation, but due to chemical causes.
Of the numberless attempts made to elucidate the phenomena of
electricity, in connection with the formation of thunderstorms, none
seem more worthy of regard, and of thoughtful consideration, than
those of Jean Athanase Peltier, a French savant, little known to the
general world. Born in 1785, he occupied his whole life, until his
death in 1845, with the study of meteorology and electricity, making,
among others, the important discovery that a current flowing through
a circuit composed of two metals joined together heats or cools the
junction according to the direction of the current. From all the
experiments upon the phenomena of electricity, to which he devoted
his life, Peltier drew the conclusion that the earth itself, and more
particularly the fiery liquid mass forming the inner bulk of it, over
which the solid crust and the ocean lie, but both thinner in comparison
than the skin of an apple, form one immense reservoir of electricity.
As light comes from the sun, generated, as we believe, by heat, so
the electric force, he held, comes from the interior of the globe,
likewise generated by heat. The atmosphere surrounding the globe,
Peltier asserted, produced no electricity whatever, nor held it, except
temporarily. But he thought it possible that it might exist, engendered
by other flaming masses than those of the earth’s interior, in the
interminable planetary spaces, which no astronomer can measure, and of
which imagination itself, in its loftiest flights, can form no more
conception than the finite ever can of the infinite. On the whole,
Peltier’s explanation, such as it is, may fairly be accepted, in the
present state of the scientific investigation, as one of the best that
can be given. For the rest, men must content themselves to study the
phenomena of electricity, and to regard it simply as one of the great,
if mysterious, forces of nature.
[Illustration]