THE LEYDEN JAR DISCOVERED
As yet no one had discovered that electricity could be stored, or
generated in any way other than by some friction device. But very
soon
two experimenters, Dean von Kleist, of Camin,
Pieter
van Musschenbroek, the famous teacher of
apparently independently, made the discovery of what has been
known ever since as the Leyden jar. And although Musschenbroek is
sometimes credited with being the discoverer, there can be no
doubt that Von Kleist's discovery antedated his by a few months
at least.
Von Kleist found that by a device made of a narrow-necked bottle
containing alcohol or mercury, into which an iron nail was
inserted, be was able to retain the charge of electricity, after
electrifying this apparatus with the frictional machine. He made
also a similar device, more closely resembling the modern Leyden
jar, from a thermometer tube partly filled with water and a wire
tipped with a ball of lead. With these devices he found that he
could retain the charge of electricity for several hours, and
could produce the usual electrical manifestations, even to
igniting spirits, quite as well as with the frictional machine.
These experiments were first made in October, 1745, and after a
month of further experimenting, Von Kleist sent the following
account of them to several of the leading scientists, among
others, Dr. Lieberkuhn, in Berlin, and Dr. Kruger, of Halle.
"When a nail, or a piece of thick brass wire, is put into a small
apothecary's phial and electrified, remarkable effects follow;
but the phial must be very dry, or warm. I commonly rub it over
beforehand with a finger on which I put some pounded chalk. If a
little mercury or a few drops of spirit of wine be put into it,
the experiment succeeds better. As soon as this phial and nail
are removed from the electrifying-glass, or the prime conductor,
to which it has been exposed, is taken away, it throws out a
pencil of flame so long that, with this burning machine in my
hand, I have taken above sixty steps in walking about my room.
When it is electrified strongly, I can take it into another room
and there fire spirits of wine with it. If while it is
electrifying I put my finger, or a piece of gold which I hold in
my hand, to the nail, I receive a shock which stuns my arms and
shoulders.
"A tin tube, or a man, placed upon electrics, is electrified much
stronger by this means than in the common way. When I present
this phial and nail to a tin tube, which I have, fifteen feet
long, nothing but experience can make a person believe how
strongly it is electrified. I am persuaded," he adds, "that in
this manner Mr. Bose would not have taken a second electrical
kiss. Two thin glasses have been broken by the shock of it. It
appears to me very extraordinary, that when this phial and nail
are in contact with either conducting or non-conducting matter,
the strong shock does not follow. I have cemented it to wood,
metal, glass, sealing-wax, etc., when I have electrified without
any great effect. The human body, therefore, must contribute
something to it. This opinion is confirmed by my observing that
unless I hold the phial in my hand I cannot fire spirits of wine
with it."[2]
But it seems that none of the men who saw this account were able
to repeat the experiment and produce the effects claimed by Von
Kleist, and probably for this reason the discovery of the obscure
Pomeranian was for a time lost sight of.
Musschenbroek's discovery was made within a short time after Von
Kleist's--in fact, only a matter of about two months later. But
the difference in the reputations of the two discoverers insured
a very different reception for their discoveries. Musschenbroek
was one of the foremost teachers of Europe, and so widely known
that the great universities vied with each other, and kings were
bidding, for his services. Naturally, any discovery made by such
a famous person would soon be heralded from one end of Europe to
the other. And so when this professor of Leyden made his
discovery, the apparatus came to be called the "Leyden jar," for
want of a better name. There can be little doubt that
Musschenbroek made his discovery entirely independently of any
knowledge of Von Kleist's, or, for that matter, without ever
having heard of the Pomeranian, and his actions in the matter are
entirely honorable.
His discovery was the result of an accident. While experimenting
to determine the strength of electricity he suspended a
gun-barrel, which he charged with electricity from a revolving
glass globe. From the end of the gun-barrel opposite the globe
was a brass wire, which extended into a glass jar partly filled
with water. Musschenbroek held in one hand this jar, while with
the other he attempted to draw sparks from the barrel. Suddenly
he received a shock in the hand holding the jar, that "shook him
like a stroke of lightning," and for a moment made him believe
that "he was done for." Continuing his experiments, nevertheless,
he found that if the jar were placed on a piece of metal on the
table, a shock would be received by touching this piece of metal
with one hand and touching the wire with the other--that is, a
path was made for the electrical discharge through the body. This
was practically the same experiment as made by Von Kleist with
his bottle and nail, but carried one step farther, as it showed
that the "jar" need not necessarily be held in the hand, as
believed by Von Kleist. Further experiments, continued by many
philosophers at the time, revealed what Von Kleist had already
pointed out, that the electrified jar remained charged for some
time.
Soon after this Daniel Gralath, wishing to obtain stronger
discharges than could be had from a single Leyden jar, conceived
the idea of combining several jars, thus for the first time
grouping the generators in a "battery" which produced a discharge
strong enough to kill birds and small animals. He also attempted
to measure the strength of the discharges, but soon gave it up in
despair, and the solution of this problem was left for late
nineteenth-century scientists.
The advent of the Leyden jar, which made it possible to produce
strong electrical discharges from a small and comparatively
simple device, was followed by more spectacular demonstrations of
various kinds all over Europe. These exhibitions aroused the
interest of the kings and noblemen, so that electricity no longer
remained a "plaything of the philosophers" alone, but of kings as
well. A favorite demonstration was that of sending the electrical
discharge through long lines of soldiers linked together by
pieces of wire, the discharge causing them to "spring into the
air simultaneously" in a most astonishing manner. A certain monk
in Paris prepared a most elaborate series of demonstrations for
the amusement of the king, among other things linking together an
entire regiment of nine hundred men, causing them to perform
simultaneous springs and contortions in a manner most amusing to
the royal guests. But not all the experiments being made were of
a purely spectacular character, although most of them
accomplished little except in a negative way. The famous Abbe
Nollet, for example, combined useful experiments with spectacular
demonstrations, thus keeping up popular interest while aiding the
cause of scientific electricity.
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