Société Genevoise 103 Meter Standard

This meter standard is made from invar, an alloy of nickel (36%), iron (63.5%), and manganese (0.5%) invented by Swiss scientist Charles Édouard Guillaume in 1896 and known for its low coefficient of thermal expansion. Although the metal remains uniform in size throughout changes in temperature, it is prone to corrosion from acid and so a note received with the instrument warns users not to touch it with bare hands.

The bar is H-shaped in cross-section to minimize bending and warping of the scale. On one side, the crossbar is divided to millimeters and numbered by ones from 0 to 100. (The mm lines are very faint.) The lower left corner of the frame on this side is marked: S.I.P. GENEVE. On the other side, the top left corner of the frame is marked: INVAR. The crossbar is marked: 103. Extra cushioning has been added to a wooden case.

The Société Genevoise d'Instruments de Physique (SIP, or Geneva Society of Physical Instruments) began manufacturing scientific instruments in 1862. In 1870 the firm expanded into electrical equipment and into precision measuring devices. It advertised invar meter standards in 1900, although the apparent equivalent of this example is listed as model number 131. It sold for 300 francs. No model number 103 is listed in the 1900 catalog.

The Weston Electrical Instrument Company, established by chemist Edward Weston in Newark, N.J., in 1888, owned this object and may have used it as the firm's house standard. The company was best known for photographic light meters until its product lines were disbursed to other firms in a series of takeovers in the early 1980s. Charles J. Mulhern (1925–1994), an engineer at Weston, collected this object when the company's museum was dismantled in the 1970s.

References: Illustrated Price List of Physical and Mechanical Instruments Made by the Société Genevoise(Geneva, 1900), 20–22; Bénédict Frommel, "Société genevoise d'instruments de physique (SIP)," Dictionnaire historique de la Suisse, Berne, 1998–2012, http://www.hls-dhs-dss.ch/textes/f/F41920.php; accession file.

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