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Volta's work was characterized throughout by forethought; there was no empiricism, nothing due to mere chance. In his endeavour to test his theory, he invented the "condensing electroscope" by which he established the fundamental fact that when two dissimilar conductors, e.g. zinc and copper, are brought together in air and then separated, the zinc is found to have a small positive, and the copper an equal negative charge, a result which has been confirmed by subsequent investigators working with more delicate instruments, notably by Lord Kelvin. Anterior to this, in 1775, Volta devised his electrophorus by means of which, given a small initial electrification, mechanical work may be transformed at will into energy of electrostatic charge. Though the principle involved was known to Canton of London in 1753, and though Wilcke of Sweden described an electrophorus in 1762, Volta's was the first practical machine of the kind and, therefore, the prototype of the rotary influence machines of the present day, such as the Holtz, the Voss, and the Wimshurst. In 1777 he proposed a system of electric telegraphy in which signals were to be transmitted by means of his electrophorus over a line extending from Como to Milan. The first use of static electricity for telegraphic purposes was, however, suggested in the "Scots Magazine" for 1753 and carried out on a small scale in 1774 by Lesage of Geneva.
In seeking further experimental evidence in favour of his contact theory, Volta was led to the greatest of his inventions, the voltaic "pile", which he described in a communication of 20 March, 1800, to Sir Joseph Banks, President of the Royal Society of London. Consisting as it did of a number of discs of zinc and copper separated by pieces of wet cloth and arranged in a vertical column, it was appropriately called a "pile"; a more efficient arrangement was, however soon found by Volta in the "crown of cups". The voltaic battery of 1800 marks an epoch in physical theory as well as in the application of science to the welfare of mankind. Though Volta lived twenty-seven years after the crowning invention of his life, it is a significant fact that he added nothing of note to his great work, leaving to Carlisle and Nicholson in 1800 to use the current furnished by a "pile" to decompose water; to Sir Humphry Davy in 1807 to separate sodium and potassium from their alkalis by the same means; and to Oersted of Copenhagen the cardinal discovery in 1820 of the magnetic effect of the electrical current.
Honours were showered on Volta by the academies and learned societies of Europe. Napoleon invited him to Paris in 1801 and made him an associate member of the Institut de France and later a senator of the Kingdom of Italy. In 1815 the Emperor of Austria appointed him director of the philosophical faculty of the University of Padua, a dignity which he resigned four years later in order to retire into private life. In the summer of 1899, the centenary of the invention of the voltaic battery, an exposition was held in Como of electrical apparatus constructed and used by Volta in his investigations, but unfortunately a fire broke out and many of these heirlooms of science were destroyed. Three practical units have been named after Catholic electrical pioneers; the volt, the unit of electrical pressure, in honour of Volta; the coulomb, the unit of electrical quantity, in honour of Charles Augustin de Coulomb; and the ampere, the unit of current, in honour of André-Marie Ampère.
BIANCHI AND MOCCHETTI, Vita de Volta (Como, 1829-32); ZANINO VOLTA, Alessandro Volta (Milan, 1875); IDEM, Alessandro Volta à Parigi (Milan, 1879).