In approximately 1795, Jean-Charles de Borda, in his capacity of Guardian of Standards, and on instruction by the French Academy of Sciences, constructed two length standards. One, designated the Mètre des Archives, which ultimately became the standard meter for the world, and another, called the Module, a bar two toises long, with the meter defined as a multiple of the toise. Until 1880, most of Europe, specifically including France, used this meter, defined in terms of Borda's Module, as a standard; however, England defined a legal metre (to use British spelling) in terms of a copy of the Mètre des Archives.
In 1875, the International Bureau of Weights and Measures, located in Paris, France, was established. It decided to adopt an "International meter," and in about 1883, a standard was prepared, which, being based on the Mètre des Archives, actually changed the legal value of the meter in those countries that had been using a meter defined in terms of the Module.
In 1896, Benoît and Chaney compared this "International meter" with the British Imperial Standard Yard and derived the equivalence of 1 Inernational meter = 39.370113 Imperial inches = 3.28084275 Imperial feet. Inverting that ratio, one British foot = 0.3047997348 international meters. This length is sometimes termed the Benoît foot. It has been employed in geodesy.
It should be noted that Clarke had derived a length of the older French legal meter (based on the toise) as 39.370432 British Imperial inches. Comparing these values, and assuming that both Clarke's and Benoît and Chaney's determinations were accurate, the French legal meter was equal to 1.0000081 of the new international meters.
- ↑ Tomasz Zakiewicz, The Cape Geodetic Standards and Their Impact on Africa
- ↑ G. T. McCaw (1932). Empire Survey Review 2 (14): 472-484. (cited in Zakiewicz)
- ↑ Georepository.com article "Unit: British foot (Benoit 1895 A)"