Pavia-Como, 12 September 1999 A.Volta between Natural Philosophy and Physics Fabio Bevilacqua

Contents 1) Introduction (13) 2)Travelling and Corresponding (8) 3)Cultural and Scientific Context (4) 4)The Roots of Volta’s Research Program (9) 5)Debating with Beccaria (4) 6)New Researches (4) 7)Electrostatics (4) 8) Debate w. Coulomb (12) 9)Factorisation (25) 10) Debate w. Galvani (28) 11) Final steps (6) 12) Volta’s theoretical legacy (5) 13) Primary Sources (6) 14) Historiography (6) 15) Celebrations (6) 16) Volta on the Web (2)

Alessandro Volta ( )

Theory and experiments A.Volta L.Galvani A.Coulomb

Extraordinary Life on the European stage Religious family; early extensive scientific correspondence; no university education; University chair at 33 extensive travelling; rich sentimental life; Copley medal

Closely witnessing revolutionary changes What was going on? The revolution in physics was matched by a political one –A period of enlightened reforms was followed by a revolution, a new empire, the restoration

Enlightened Despotism

A tenure for the quantifiers Austrian Reforms: Pavia University and the professionalization of the Baconian sciences: Scarpa, Spallanzani, Scopoli, Brugnatelli, G.Fontana, M.Fontana, Frank, Brunacci

1778: Volta’s chair in experimental physics: cabinet and theatre

Napoleon’s military tourism

L’Institut reopens

Volta and Napoleon 1796: The battle of Lodi (near Pavia) 1801: Institut de France

Institutional changes Mathematising the Baconian sciences: Paris Research and teaching: Berlin

The Context: Institutional

1815: Restoration

Travelling and Meeting: 1777 and 1787, Switzerland Voltaire, Senebier, de Saussure Genêve, Basel, Strasbourg, Berne

Sept April1782: Switzerland, Pays Bas, France September: Genêve October: Paris November: Bruxelles, meeting Magellan November: Antwerp, The Hague 28 November: Harlem, meeting Van Marum Back to Paris

December April 1782: Paris Lavoisier, Laplace, Franklin, Buffon, Sage, Le Roy Synthesis of water

April-June 1782: Great Britain Meeting Magellan in Bruxelles, Louvain and then London; June: Bristol Birmingham: Priestley, Boulton and Watt

July-November 1784: Wien, Berlin, Goettingen Wien: Joseph II Helmstaedt: Crell Brunswick: Duchess (mother) Goettingen : October, Lichtenberg Gotha: Duke and Prince Genêve: Tissot, Saussure

1801-2: Paris, Lyon, Genêve Paris: Bonaparte, Chaptal, Berthollet, Fourcroy, Guyton, Laplace, Seguin, La Metherie Lyon: Chaptal

Corresponding Priestley, Franklin, Nollet Van Marum Lichtenberg Magellan Gren Banks

1763: An early start Joseph Priestley Gianbattista Beccaria Jean Antoine Nollet

A closer look at the scientific context Classical and Baconian Old “classical” mathe- matized sciences: me- chanics, astronomy, optics, harmony (fisica generale: quadrivium) New “baconian” experimental sciences: electricity, magnetism, thermology, chemistry (fisica particolare (experimental)) Two epistemological criteria: sensible and occult (medieval); primary and secondary (Galileian) Three traditions of natural philosophy in the classical fields:

Baconian electricity

An older epistemological context Scholastic epistemology: sensible versus occult qualities Quantification of sensible qualities through intensive and extensive factors Galileian epistemology applied in Classical Sciences: primary (quantifiable) and secondary (non quantifiable) qualities. Problem: often primary are “occult” Baconian Sciences: still sensible versus occult. Problem: first make it sensible

A wider cultural context: Descartes Leibniz Newton

Volta’s Research Programme The received view A hint Origins Theoretical works

The Received View Classical sciences (general physics, quadrivium) challenged by Baconian Sciences (particular, experimental physics) undergoing a process of quantification and mathematization along Newtonian- Coulombian lines Enlightenment and quantification “Standard Model” of particles and fluids and interactions

The Roots of Volta’s Tension A hint from Massardi, Volpati, Polvani: Use of intensive (non additive) and extensive (additive) factors, like temperature and heat My approach: We cannot confine ourselves to models and analogies General regulative principles have to be taken in account

Origins: Oresme Oresme: “latitude referring to the intensity of a quality or motion and longitude to its extension either in the qualified body or mobile or in time”; “Oresme also differed from his Oxford predecessors in that his primary measure of qualities and motions became not intensity, pure and simple, or velocity, pure and simple, but the so-called "quantity of quality” or "quantity of motion," where the quantity of a quality or motion was equal to its intensity times its extension”

Origins: Oresme “To consider such a quantity of quality or motion was an important step away from the ideas of the Oxford authors, for whom the product of an intensity times an extension had no real ontological significance; In the decades after the appearance of the works of Heytesbury Swineshead, and Oresme, discussions of the intension, remission, latitudes, and degrees of forms were quite common, and many rather elementary handbooks of the basic concepts of their works were compiled”

Origins: Leibniz “Per dare un saggio delle mie concezioni mi è sufficiente spiegare che la nozione di forza o virtù, che i Tedeschi chiamano Kraft e i Francesi force, e per esporre la quale io ho elaborato una scienza particolare della dinamica, chiarisce di molto la comprensione del concetto di sostanza. In effetti la forza differisce dal concetto di mera potenza così familiare alla Scolastica in quanto questa potenzialità o facoltà non è altro che una possibilità pronta ad agire, la quale necessita,

Origins: Leibniz però, di un'eccitazione o di uno stimolo esterni per poter passare all'atto. Ma la forza attiva contiene un certo atto o entelechia e si trova a mezza strada tra la facoltà dell'agire e l'azione stessa; essa implica lo sforzo, e così passa di per se stessa all'operazione; nè ha bisogno di alcun ausilio ma semplicemente della rimozione dell'impedimento”

The Context: Scientific

Origins of Volta’s Theory: Beccaria

Volta’s Theory: 1769 De Vi l'attrazione del fluido elettrico...non segue quella attrazione universale proporzionale alla massa e decrescente secondo il quadrato delle distanze ad una notevole distanza

Volta’s Theory: 1769 De Vi il fuoco sovrabbondante, cioè tutto quello che supera la saturità rispettiva, deve trasmettersi agli altri corpi coi quali comunica, affinché si conservi l'equilibrio delle forze il fuoco sovrabbondante da questa entra in quello, in ragione della sua capacità sebbene vi tenda con grande sforzo

Volta’s Theory: 1771Novus forze mutue... non meccaniche all’accumularsi di una certa quantità di fuoco estraneo in una delle facce, altrettanto fuoco nativo si sforza di allontanarsi da quella opposta ricavavo felicemente anche tutti i fenomeni dell’atmosfera elettrica

1775: Electrophorus

1776: Methane

1777: Inflammable air pistol

1777: Inflammable air eudiometer

1778: Chair at Pavia University

Volta’s Theory:1778 De Saussure "quanto più d'azione e di giri della macchina accade d'impiegare per far salire il pendolino ad una determinata tensione, tanto maggiore vuol dirsi che sia la capacità del conduttore" "Non c'è altra energia che quella che chiamo tensione di elettricità, che è poi lo stesso sforzo di spignersi fuori

Volta’s Theory: Sull’elettrometria si forma d'attorno a quel corpo così elettrizzato un'atmosfera attiva,... estendendo a considerabile distanza una cotal forza o potenza, per cui qualsiasi altro corpo immerso in cotesta sfera di attività ne viene più o meno affetto

1780: Condenser Electroscope

1782: Q=CT

Volta and Coulomb:Force and Tension

Coulomb’s 1785 Newtonian force law: The Torsion Balance