Mendenhall Order

The Mendenhall Order was the regulation, which the United States of America, the national definitions for the basic unit of length yard and the ground unit avoirdupois pound official duties and, based on these definitions the metric system. This Decree was promulgated on 5 April 1893 by Thomas Corwin Mendenhall, Superintendent of the U.S. Coast and Geodetic Survey with the permission of the Treasury John Griffin Carlisle. It was published in Bulletin No.. 26 - Fundamental Standards of Length and Mass of the survey.

Standards prior to Regulation

In October 1834, the Houses of Parliament of the United Kingdom were destroyed by fire, with the British standards for length and mass were destroyed. As 1855 Spare Normal were completed, they gave two samples of the yards and one of the avoirdupois pound to the United States. A Yard officially became a standard length unit of the USA. Both yards were brought back to England in 1876 and 1888 and compared with the Imperial Yard of the United Kingdom. That the U.S. on suitable pound pattern was consistent with the pound the U.S. Mint agreed ( U.S. Mint ); there is conflicting information, which it has been the national standard.

There was in any case own standards for length and mass in the Anglo-Saxon system of measurement and other for the metric system, which were kept by the Office of Weights and Measures of the U.S. Coast and Geodetic Survey: the iron " Committee meters " and the " Arago kilogram " of platinum.

First Steps to metric system

In 1866 the U.S. Congress passed a law allowing the use of the metric system, but not prescribe it. Included was a conversion table between traditional and metric units.

A series of conferences in France 1870-1875 led to the signing of the Metre Convention and the establishment of the International Bureau of Weights and Measures, BIPM abbreviated after the French. The BIPM was meter and kilogram standards for all states that had signed the agreement, finished; two meter bars and two kilogram pieces for the U.S. came in 1890 there, and broke Comittee meters and Arago kilogram as national standards of the metric system from.

Reasons for the change

The standard of the Imperial Yard 1855 turned out to be unstable: it was shortened by measurable amounts. The pound - weight piece of the coin was also found to be unsuitable. Therefore, it was the Office of Weights and Measures already several years before the regulation was issued, virtually forced to resort to the metric standards because of their superior stability. In addition, these better suitable to perform precision comparisons. The Office was the conversion tables from the Act of 1866 for correctly and used them to derive length and mass in the Anglo-Saxon system of units of the metric normal.

The translations were and

The Mendenhall Order was the formal act that explain the norm since 1866, proven in practice and deliberately kept simple conversion factors.

In the following months, it was found that the deviation from the British definition of the pound was still unacceptable. Although the yard also more from, but you stuck with it, the pounds but it took the British definition, which reported more decimal places:

March 21, 1894, the equality of British and U.S. pound was declared and the Office of Weights and Measures was not wholly correctly rounded conversion factor:

The exact term in brackets of the last places ( 7989 ..) would have been correct to (80 ) to round, but may correspond to a British source.

Improving conversions

The final specifications for the USA from 1894 remained unchanged for 65 years, but improvements in measurement technology and increasing accuracy requirements in practice were the different definitions of the same basic units in the economies with yard and pound come to markedly different measurements. This resulted in particular in trade in goods of the Commonwealth to the fact that precise standard and machine parts with fittings such as ball bearings or metering devices were no longer interchangeable. Scientific communication was also affected because research results were not reproducible and it threatened practical reasons that different disciplines and sectors of high technology products and their results published increasingly in the metric system. To obtain the standard sovereignty in technologically closed Commonwealth market, the Commonwealth countries Australia, Canada, New Zealand, South Africa and United Kingdom have set unifications:

And

With effect from July 1, 1959 defined the United States of America that the U.S. yard the International Yard and the U.S. International Pound the Pound equivalent. In the States where yard and pound in everyday life play a role in these international definitions are also common.

Maßnormale and measurement systems

Mendenhall decreed that the normal at which the length and mass determinations oriented, switched from certain Yard and Pound patterns at certain meters and kilograms patterns. However, a person was initiated outside of the Office of Weights and Measures to instead of the Anglo-Saxon system of measurement using the metric system.