1890, and were adopted as national standards. Reasons for the change The imperial standard yard of 1855 was found to be unstable and shortening by measurable amounts. Also, the mint pound was found to be “likewise unfit for use.” For several years before the Mendenhall order was actually issued, the Office of Weights and Measures was “practically forced” to use the metric standards because of their superior stability, and because they were better designed for carrying out precision comparisons. The Office found that the conversion tables in the 1866 law were satisfactory and used them to derive customary length and mass from the metric standards. The conversions were 1 yard = meter and 1 pound = kilogram. Therefore, the Mendenhall order amounted to a formal announcement of a change that had already occurred in practice. Another motivation for the order was that later that year, in August 1893, an International Electrical Congress would be held in connection with the World's Fair in Chicago. Associated with the Congress would be a "Chamber of Delegates", officially organized for the purpose of coming to an international agreement on units of electrical quantities. As Mendenhall wrote, Refinement of the conversions The definitions of 1893 remained unchanged for 66 years, but increasing precision in measurements gradually made the differences in the standards in use in English-speaking countries important. By the international yard and pound agreement of July 1, 1959, Australia, Canada, New Zealand, South Africa, the United Kingdom, and the United States agreed that 1 yard = 0.9144 meter and that 1 avoirdupois pound = kilogram (but see U.S. survey foot). Standards versus systems Mendenhall ordered that the standards used for the most accurate length and mass comparison change from certain yard and pound objects to certain meter and kilogram objects, but did not require anyone outside of the Office of Weights and Measures to change from the customary units to the metric system. See also Metric system in the United States References Footnotes Further reading Mendenhall, T. C. (1893). "Fundamental Standards of Length and Mass". Reprinted in Barbrow, Louis E. and Judson, Lewis V. (1976). "Weights and measures standards of the United States: A brief history (NBS Special Publication 447)." Washington D.C.: Superintendent of Documents. pp. 28–29. Economic history of the United States Metrication in the United States 1893 in the United States 1893 documents