Volta
‘The language of experiment is more authoritative than any reasoning; facts can destroy our ratiocination—not vice versa.’–Alessandro Volta
Lake Como (Lago di Como in Italian) in Lombardy, Italy, not far from Milan, has been a popular resort and tourist destination since Roman times. Many international celebrities have or have had homes on the shores of this beautiful lake. It is also famous for the capture and assassination in 1945 of Benito Mussolini and his mistress Clara Petacci by Partisans at Dongo on its north-western shore.
The town of Como on the southern shore, from which the lake derives its name, has scientific history associated with it as it was the home town of Pliny the Elder (the author of Naturalis Historia, a 37-volume compendium of ancient science) and of Pliny the Younger. However, the distinction of being the greatest and most famous son of Como must go to Alessandro Giuseppe Antonio Anastasio Volta, acknowledged as one of the greatest scientists of all time, whose discoveries, works and experiments have had a profound influence on the world as we know it today. It is not surprising, then, that the town of Como has a town square, a street and a school named after him and a great museum housing a collection of his works.
Alessandro Volta (referred to henceforth as Volta) was born in 1745 into a noble family of Lombardy. The accepted norm and practice of the day was for the local nobility to be deeply involved in religious matters. In many cases, the nobility, such as Volta’s family, even became part of the Church or, at the very least, members of societies closely associated with it. This enabled the combination of Church and nobility to maintain control over all major matters concerning local society, including cultural, social, educational and economic.
By the time Volta was ready to go to high school, Como had many monasteries and other religious institutions. Given the nexus between Church and nobility, it is not surprising that as a teenager Volta became a boarder at a Jesuit educational institution and was enrolled for a short period in one of the local seminaries. With almost all teachers at these institutions being priests, it may be safely assumed that any basic education in physics or natural philosophy received by Volta would have been influenced by the beliefs of the Church of the time.
It would also perhaps be safe to assume that Volta would have been familiar with the works of Pliny the Elder, who, as stated, was also from Como. In his compendium Naturalis Historia, first printed in 1499, Pliny covered topics ranging from geography, zoology and botany to mining and mineralogy. However, since Pliny himself does not seem to have been a natural philosopher, there is very little chance that Volta’s endeavours during his lifetime would in any way have been influenced by Pliny the Elder.
What is known and recorded is the influence another student at a Jesuit institution in Como had on Volta. This was Giulio Cesare Gattoni. Volta befriended Gattoni during their student days in Como. Gattoni had an inclination towards the study of science and electric phenomena, which was quite the rage during what would come to be called the Age of Enlightenment.
In 1764, Gattoni rented a building (part of the still-standing Porta Nuova Tower) from the municipality of Como to establish a laboratory and library, where Volta was a frequent visitor. In 1768, Gattoni set up the first lightning rod in his Como laboratory. It is thus almost certain that Volta’s friendship with Gattoni and the visits to and the use of his laboratory sparked in Volta a deep interest in the field of electricity.
But possibly the most important influence on the young Volta and his experimentation in the field of electricity was another Italian priest turned natural philosopher/scientist, Giambatista Beccaria.1 Beccaria had experimented with electricity and written papers and books on the subject. He was also a contemporary as well as a correspondent of the great Benjamin Franklin, another pioneer in the field of electricity.
It was the Age of Enlightenment. Electricity as a field of study was all the vogue. Some of the greatest minds, including von Guericke, Gray, Dufay, Musschenbroek, Nollet, Benjamin Franklin, Delor, Dalibard and Beccaria were considered pioneers in the field. In 1763, Volta, at the very young age of 17, no doubt impressed by all he had read about electricity, wrote a letter to Beccaria (then holding the Chair of Physics at Turin University) about his thoughts on electricity. Sadly, Beccaria did not deign to reply.
Volta was quite an avid correspondent and prolific letter writer. He wrote to many scientific personalities of the day in addition to Beccaria. He sent letters, papers and notes to the French scientist Jean-Antoine Nollet. Later he would correspond with Professor Carlo Barletti of the University of Pavia, the Italian physicist Giovani Aldini, Joseph Priestley, Joseph Banks of the Royal Society in London and several others in Europe and Britain. Of course, it helped that Volta was fluent in several languages, with a very good knowledge of Latin, French, English, German, Dutch and Spanish, in addition to his native Italian.
In 1765, Volta used Gattoni’s laboratory for his own experiments. In the same year, at the age of 20, Volta wrote possibly his first scientific paper, on static electricity produced by rubbing two different substances. Again corresponding with Beccaria, Volta this time received an encouraging response. In 1769 he published a treatise in Latin entitled On the attractive force of the electric fire, in the form of a letter to Beccaria, who from then on became a sort of mentor to Volta.2
At about this time, it appears, Volta started to question blind superstition about commonly observed phenomena. He started to write his scientific thoughts, strangely, in the form of poetry. This might have been out of due caution as the administration in Lombardy changed between Austria and France and then back again to Austria. Further, of course, Volta had to be wary of the sensitivities of the Church, to which many of his kinfolk belonged, and because he had studied in a Church-affiliated school.
In his first known work of poetry, ‘Volta ascribes to the science of electricity a key role in the portrait of the age of reason….If (Benjamin) Franklin had rebutted Lucretius on the cause of lightning, Volta clearly saw Franklin’s electrical explanation of lightning as yet another step in the Lucretian fight for freeing humanity from superstition.’3
With a series of successful experiments and innovations, and with his relentless exchange of letters with renowned natural philosophers and men of science of the time, Volta soon acquired a reputation as a man of science with good credentials in the developing domain of electricity. This, coupled with the backing of some of his mentors as well as other influential contacts in the world of academia, Volta’s appointment in 1774 as superintendent in the regional secondary educational system.
Volta’s Electrophorus
Volta, was fascinated reading about the works of Aepinus (Franz Maria), also known as Epino, a German scientist who in his 1759 book Tentamen Theoriae Electricitatis et Magnetism (An Attempt at the Theory of Electricity and Magnetism) describes what today we would call a parallel plate capacitor.4
In 1775 Volta publicly announced (in a letter sent to Joseph Priestley) the development of his own version of a device that would store electric charge. He used the principle of electrostatic induction, or ‘influence’ (as Volta described it), rather than the known version of generating electrostatic charge by rubbing two materials together. He called it the electrophorus.
Volta’s so-called perpetual electrophorus comprised a sort of cake of resin placed between two metallic discs. First, the bottom metallic disc is rubbed by wool to give its upper surface a negative charge. When the upper metallic disc is brought close to the bottom disc, its lower surface acquires a positive charge by the process of induction. The negative charge on the other side is drained off by the simple expedient of an ‘earthing’ connection. The remaining induced positive charge on the upper disc is now usable to, for example, charge a Leyden jar.
After discharging the positive charge from the upper metallic disc, it may be recharged following the same process, over and over again. As a result the device came to be known as Volta’s perpetual electrophorus. It has been described as ‘the most intriguing electrical device since the Leyden jar’.5
It is believed that Volta’s development of the electrophorus was also greatly influenced by the works of Joseph Priestley. Volta had experimented first with a wood disc (instead of the resin disc), but on reading Priestley’s History of Electricity, he noted that this approach had already been tried. He switched to using baked cardboard with some success and wrote a letter to Priestley describing his work.
Priestley wrote back promptly to say, ‘The idea of your machine made of cardboard impressed me. That is why I had it built for me, and I was much surprised to see its effects.’6
Volta experimented with many dielectrics, vitreous as well as resinous. These included silk, glass and resin before settling on the latter, which turned out to be the most efficient solution at that time. It must be stated here that Volta was not the inventor of the electrophorus or its equivalent. We have already mentioned Aepinus. But Johan Carl Wilcke, a Swedish professor, and several others had also developed such devices. However, Volta was the first to come up with a so-called influence electrophorus.7
Credit must be given to Volta for having come up with an ingeniously simple but robust machine that could easily be reproduced in numbers, so much so that building a simple electrophorus is a popular physics laboratory and hobby lesson in many schools worldwide today.
In its fundamental form, Volta’s electrophorus may be seen as an electrostatic charge generator which in its time was seen as a replacement for the Leyden jar. Today, as stated earlier, it may be viewed as primarily a laboratory teaching device on the subject of electrostatic charge. Yet, it was a precursor to several interesting applications using efficient but simple electrostatic charge generators.
Such electrostatic generators also find applications in, for example, economical electrostatic non-permanent bonding using static electricity, food sterilization and some medical laboratory applications. Edward Nairne, British scientist and inventor (who, along with Isaac Newton, invented the rubber eraser), developed a version of the electrophorus shortly after Volta. This contraption was reportedly used for treatment of ‘nervous disorders’. Apparently, the device was used to deliver a controlled electric shock to a patient suffering from a mental ailment. At the time of writing (in 2015), one such machine is actually being offered for sale on an antiques Web site.8
Even in modern times, a review of the literature suggests that an electrophorus is used for various other medical treatment of patients. Walter John Turrell, in his book on electrotherapy, writes, ‘There is much evidence to show that the raising of blood pressure, due to the stimulation of the afferent nerves of the skin [when a charge is applied from an electrophorus machine] is the primary and main effect of the static charge. For instance, it has been recognized for many years that this form of treatment is especially indicated for cases of neurasthenia with low blood pressure, that it is also indicated as a general stimulant or tonic when the patient is exhausted by prolonged pain, anxiety, or overwork, or where sleeplessness has resulted from either of these causes.’9
The electrophorus has other interesting connections. Derivatives of the electrophorus and its technology have found application in spray painting, the removal of soot from chimneys, photocopiers and inkjet printers. Tesla, as we will read in Chap. 2 of this book, also used one in his experiments for his patent on radiant energy.
The so-called electric eel fish (Electrophorus electricus) is famous for its ability to generate a powerful electric shock. This aspect of ‘animal electricity’ developed into an interesting field of...