Техническое чтение для энергетиков. Бухарова Г.П. - 21 стр.

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23
conductor on the house of a Philadelphia business man.
His theory was that during a thunderstorm a continual radiation of electricity
from the earth through the metal of the lightning-conductor would take place, thus
equalizing the different potentials of the air and the earth so that the violent discharge
of the lightning would be avoided. The modern theory, however, is that the lightning-
conductor simply offers to the electric tension a path of low resistance for quiet
neutralization. At any rate – even if Franklin's theory was wrong – his invention
worked.
Yet its general introduction in America and Europe was delayed by all kinds of
superstitions and objections: if God wanted to punish someone by making the
lightning-strike his house, how could Man dare to interfere? By 1782, however, all
the public buildings in Philadelphia, first capital of the USA, had been equipped with
Franklin's lightning-conductors, except the French Embassy. In that year this house
was struck by lightning and an official killed. Franklin had won the day.
It was he who introduced the idea of 'positive' and 'negative' electricity, based
on the attraction and repulsion of electrified objects. A French physicist, Charles
Augustin de Coulomb, studied these forces between charged objects, which are
proportional to the charge and the distance between the objects; he invented the
torsion balance for measuring the force of electric and magnetic attraction. In his
honour, the practical unit of quantity of electricity was named after him.
To scientists and laymen alike, however, this phenomenon of 'action at a
distance' caused by electric and magnetic forces was still rather mysterious. What was
it really? In 1780, one of the greatest scientific fallacies of all times seemed to
provide the answer. Aloisio Galvani, professor of medicine at Bologna, was lecturing
to his students at his home while his wife was skinning frogs, the professor's favourite
dish, for dinner with his scalpel in the adjoining kitchen. As she listened to the lecture
the scalpel fell from her hand on to the frog's thigh, touching the zinc plate at the
same time. The dead frog jerked violently as though trying to jump off the plate.
The signora screamed. The professor, very indignant about this interruption of
his lecture, strode into the kitchen. His wife told him what had happened, and again
let the scalpel drop on the frog. Again it twitched.
No doubt the professor was as much perplexed by this occurrence as his wife.
But there were his students, anxious to know what it was all about. Galvani could not
admit that he was unable to explain the jerking frog. So, probably on the spur of the
moment
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he explained: 'I have made a great discovery – animal electricity, the
primary source of life!'
'An intelligent woman had made an interesting observation, but the not-so-
intelligent husband drew the wrong conclusions', was the judgement of a scientific
author a few years later. Galvani made numerous and unsystematic experiments with
frogs' thighs, most of which failed to prove anything at all; in fact, the professor did
not know what to look for except his 'animal electricity'. These experiments became
all the rage in Italian society, and everybody talked about 'galvanic electricity' and
'galvanic currents' – terms which are still in use although Professor Galvani certainly
did not deserve the honour.

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