Guillaume, Charles-Edouard

SUBJECT AREA: Horology, Metallurgy

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b. 15 February 1861 Fleurier, Switzerland

d. 13 June 1938 Sèvres, France

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Swiss physicist who developed two alloys, "invar" and "elinvar", used for the temperature compensation of clocks and watches.

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Guillaume came from a family of clock-and watchmakers. He was educated at the Gymnasium in Neuchâtel and at Zurich Polytechnic, from which he received his doctorate in 1883 for a thesis on electrolytic capacitors. In the same year he joined the International Bureau of Weights and Measures at Sèvres in France, where he was to spend the rest of his working life. He retired as Director in 1936. At the bureau he was involved in distributing the national standards of the metre to countries subscribing to the General Conference on Weights and Measures that had been held in 1889. This made him aware of the crucial effect of thermal expansion on the lengths of the standards and he was prompted to look for alternative materials that would be less costly than the platinum alloys which had been used. While studying nickel steels he made the surprising discovery that the thermal expansion of certain alloy compositions was less than that of the constituent metals. This led to the development of a steel containing about 36 per cent nickel that had a very low thermal coefficient of expansion. This alloy was subsequently named "invar", an abbreviation of invariable. It was well known that changes in temperature affected the timekeeping of clocks by altering the length of the pendulum, and various attempts had been made to overcome this defect, most notably the mercury-compensated pendulum of Graham and the gridiron pendulum of Harrison. However, an invar pendulum offered a simpler and more effective method of temperature compensation and was used almost exclusively for pendulum clocks of the highest precision.

Changes in temperature can also affect the timekeeping of watches and chronometers, but this is due mainly to changes in the elasticity or stiffness of the balance spring rather than to changes in the size of the balance itself. To compensate for this effect Guillaume developed another more complex nickel alloy, "elinvar" (elasticity invariable), whose elasticity remained almost constant with changes in temperature. This had two practical consequences: the construction of watches could be simplified (by using monometallic balances) and more accurate chronometers could be made.

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Principal Honours and Distinctions

Nobel Prize for Physics 1920. Corresponding member of the Académie des Sciences. Grand Officier de la Légion d'honneur 1937. Physical Society Duddell Medal 1928. British Horological Institute Gold Medal 1930.

Bibliography

1897, "Sur la dilation des aciers au nickel", Comptes rendus hebdomadaires des séances de l'Académie des sciences 124:176.

1903, "Variations du module d"élasticité des aciers au nickel', Comptes rendus

hebdomadaires des séances de l'Académie des sciences 136:498.

"Les aciers au nickel et leurs applications à l'horlogerie", in J.Grossmann, Horlogerie théorique, Paris, Vol. II, pp. 361–414 (describes the application of invar and elinvar to horology).

Sir Richard Glazebrook (ed.), 1923 "Invar and Elinvar", Dictionary of Applied Physics, 5 vols, London, Vol. V, pp. 320–7 (a succinct account in English).

Further Reading

R.M.Hawthorne, 1989, Nobel Prize Winners, Physics, 1901–1937, ed. F.N.Magill, Pasadena, Salem Press, pp. 244–51.

See also: Le Roy, Pierre

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