To the Editor,
Sir,
I have found the recent debate surrounding Signor Fabbroni and Signor Volta’s findings
enthralling and I have spent many an hour reflecting on how their theories can aid the
medical profession. As a physician the human body is a fascination to me, but nothing
interests me more than turning my attention to a little philosophical laughing involving
electricity. I have been publishing in philosophical transactions since the time of 1750 and
my particularly interest has always lay with vibrating nerves and sensations caused by
electricity. I am hereby asking you, via your distinguished publication, to make available
to the public my new ideas involving this stimulating subject and my modest opinion on the
work of Signor Fabbroni and Signor Volta.
My most kind regards,
Erasmus Darwin
On the failure of Signor Volta’s ideas to explain the electrical theory
Experiments in electricity are a branch of philosophy which engrosses so much
conversation everywhere and is currently the subject of so many learned debates.
As a young child I would flock to the spark-filled demonstrations and since then
the workings of electricity has been of great enthralment to me. I have speculated
greatly about its medical use in my book Zoonomia. After the findings of
Galvani’s great experiment with frogs my curiosity heightened because of the
medical implications suggested in his theory. This has led me to take a keen
interest in the recent debate which is currently at the forefront of natural
philosophy. I feel it has been necessary for me to write this letter and voice my
opinion on this great subject before any more philosophers claim their support for
Volta’s mistaken contact theory of electricity. I am ashamed to think that Volta’s
theory is becoming gradually more accepted in distinguished circles, particularly
in France since the work of Monsieur Biot. I sincerely hope this letter will clarify
any misinterpretations on the subject. To make my point I will firstly compare
and contrast the current positions on the Galvanic phenomena, explain why
Volta’s pile has still been of great importance despite its incorrect theory, and
finally point out the problems in regard to Volta’s work. I anticipate that this will
put an end to much more speculation on the subject.
I believe both systems can claim a considerable amount of success, hence my
original desire to investigate them both further. The existing point of contention,
as shown in your last issue, is whether electrical power arises from the chemical
action of the fluid on the metal, as stated by Fabbroni. Or, as suggested by Volta,
electricity is set in motion by the contact of metals that have different conducting
powers. Volta has gained this belief due to the construction of his most famed
apparatus; the pile, commonly known as ‘Volta’s pile.’ I personally prefer to refer
to it as the ‘Galvanic pillar’ as I believe Volta and Galvani were pursuing similar
research theories and I feel a loyal connection to Galvani as he is a fellow medical
practitioner. The pile is constructed in resemblance to the Leiden jar but has the
clear advantage over it, in that no longer does one need to charge the apparatus
with electricity from the outside as the metal interface is the source of power.
Volta believes electricity accumulates at one end of the pile and the opposite end
is proportionally deficient. The electricity is drawn from one end to the other
from the negative copper to the positive zinc. Volta highlights that many other
metals can be substituted for copper and zinc as all either possess an excess of
negative or positive electricity. In fact, he believes all substances in nature could
acquire opposite electrical states, though in many of them the differences would
probably be too small to recognize. Volta’s idea can be considered problematic as
he attaches little importance to chemical changes within the construction of his
theory. Signor Fabbroni and Mr Wollaston address this problem through their
chemical theory of electricity. They both observed that no sensible effects are
produced by a combination of conductors which do not act chemically on each
other. They emphasise that the action of the pile is always accompanied by the
oxidation of the zinc. Hence the contact between the plates serves only to conduct
the electricity and thereby complete the circuit. Wollaston’s experiment involved
zinc and silver being immersed in the same vessel containing dilute sulphuric
acid. The zinc dissolves and yields inflammable air by decomposition of the
water. The silver not being acted upon, has no power of decomposing water, but
whenever the zinc and silver are made to touch inflammable air is also formed at
the surface on the silver. The result of this finding is that in a solution of a metal,
electricity is evolved during the action of the acid upon it and that the formation
of hydrogen gas depends on a transition between the fluid and the metal, and
hence the transfer of chemical power. This idea has since been taken up by
Nicholson and Carlisle who built the first voltaic pile outside Italy.
Despite not agreeing with Volta’s theory, I must first explain why his pile has
been of enormous benefit to me in my profession. I have always believed that
electricity should be used to treat a variety of ailments. The portability and
continual flow of electricity available from the pile has aided me in this
tremendously. I recently treated Georgiana the duchess of Devonshire with
Volta’s pile for severe pain in her tooth. I administered one hundred shocks. She
was of such an impressed nature that she requested her own voltaic pile. I believe
the efficacy of the treatment was due as much to the psychological as to the
physiological impact of the treatment. The electricity did not burn or destroy
nerves but by either the terror of the patient, or by the stimulus from so small a
pain and fear the torpid membrane of the tooth recovered its activity, and the pain
from defect of action ceased.1 In addition to the psychological stimulus I consider
the improvement in nervous or paralytic conditions due to stimulation of the
nerves by electric shocks. What most interests me regarding the object of Signor
Volta’s paper is his description of the effect his electricity is capable of producing
on our senses, particularly on our organs of taste, sight and hearing. This idea has
caused me to reflect on many physiological experiments. How do we feel
sensations? Is electricity either synonymous or closely analogous to that of the
nervous fluid?
Despite Volta’s strong connection with British philosophers, and my close
friendship with Mr Bennet who assisted Volta in his work I feel hesitant about
his theory for a number of reasons. The opinion of both Mr Wollaston and Signor
Fabbroni support my ideas medically and theoretically to a much greater extent. I
have three key criticisms of Volta’s theory; his use of mechanical forces, his
explanation of how electricity excites the organs, and his adamant sticking to the
contact theory of electricity.
Volta’s theory is completely based on the use of mechanical forces. He defines
electricity as a measure of the disturbance of the equilibrium between two metals,
equal to the tension in an open circuit. I do not believe that mechanical forces can
explain solely the action of the pile, and I have gained this opinion through my
medical investigations of the body. The application of mechanical forces to
explain the workings of the human body is also based on achieving equilibrium
and balancing the pressures of internal fluids. Along with Volta’s electrical
theory this idea is outdated as man can no longer be considered as a machine. The
theory of chemical action enables medical explanations which consider man as a
living being. In the same way as Fabbroni’s theory emphasises the weaknesses
and lack of conclusive proof in Volta’s electrical argument, I also believe the
chemical theory highlights Volta’s outdated appreciation of how the body
functions.
Another area of Volta’s theory that has interested medically is his belief that the
electric fluid when made to flow in a current in a complete circle of conductors
produces effects in the parts of the body correspondent to their excitability. This
in turn excites in particular the organs or nerves of touch, taste, sight and hearing.
Volta believes the electric fluid itself produces the sensations. With this point I
disagree. I believe that electricity is only an external stimulant which merely
increases the irritative motions, rather than supplying them with a new quantity
as suggested by Volta. I regard electricity to act in a similar way to alcohol, opium
1
Elliot
and many drugs, but also the exhilarating passions of joy and love. It increases
the exertions of all the irritative motions. I also consider Volta to be a
reductionist. He is keen to eliminate the key idea of vital forces in an animal
body. He has no confidence in animal electricity and believes he has proven that
any electricity involved is produced outside the body of the animal. His reasoning
is that as the action of a pile is electrical, and electricity created by the contact of
metals it must be the same whether it is detected by an electrometer or the sense
organs, therefore Galvani’s phenomenon was due to contact electricity rather than
animal electricity. I regard the vital forces or spirit animation as acting
throughout the nerves of our muscles in a very similar characteristic to electricity.
My final criticism of Volta’s theory is his unwillingness to advance natural
philosophy by adamantly sticking to his contact theory despite his most probable
awareness that the action of his pile is associated with chemical phenomena.
Volta has chosen not to mention this aspect in fear that it would undermine his
purely non-chemical contact explanation that an entire research theory has began
to develop around. Volta’s paper focuses its emphasis on the experiment and
apparatus surrounding his pile rather than the theory behind it. It is based on
instrumentalism as an alternative to philosophical commitment. I believe there is
an element of desiring public recognition over private achievement. Volta’s
theory has been very hastily adopted despite the many objections and clear
evidence against it provided by the chemical theory of electricity which has
greater empirical evidence and philosophical reasoning behind its explanation.
I hope this letter explains why the research theory of Signor Fabbroni should be
adopted and hopefully aid electricity in becoming a universally welcome in the
fields of medicine and physiology. I have talked very little about the work of Mr
Davy, but I consider the equilibrium theory he has produced between Volta’s and
Fabbroni’s work deserves little attention. He has been intelligent enough to
recognise that the decomposition of chemical agents is essential but he does not
believe that in cases of only chemical change electricity is exhibited. Since talking
to Mr Davy further I believe he is moving further in favour of Volta’s work and I
feel soon he will be considered a complete follower of the contact theory. I have
concluded my ideas from a combination of empirical practice, philosophical
experimentation and theorizing. I believe this is how all natural philosophers
should approach their work and not speculate conclusions without evidence.
Volta is guilty of such practice. Despite the strong support for the chemical theory
from eminent natural philosophers such a Mr Turner, Mr Wollaston and Signor
Fabbroni, all of whom state that no sensible effects are produced by a
combination of conduction which do not act chemically on each other, Signor
Volta’s contact theory still has many advocates. Hopefully in time they will be
corrected in their fallacy and that the opinions voiced in this journal will aid that
in happening. I will bring to a close this debate on a positive note that my dear
friend Priestly once said; a little philosophical laughing with electricity is
certainly, over all others, the most elegant and pleasing of experiments. They
have the most amazing variety and provide endless entertainment for one’s
friends.