Huh. Wonder what would have happened to measurement standards in this country if the pirates HADN'T attacked ...
Carleton -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of James R. Frysinger Sent: Monday, October 18, 2010 21:34 To: U.S. Metric Association Subject: [USMA:48675] Re: The metre we use The following is from my web page of metric history (not online at the present time). 1795 France adopted the metric system. An attempt to carry a copy of the earliest meter standard to the United States ended in tragic failure. Not wishing to wait for the [Delambre-Méchain] survey to be completed, France enacted a law requiring the use of the metric system, based on provisional standards. A provisional meter standard was devised based on an earlier survey of France, carried out from 1739 to 1744. Copies of this meter, graduated rulers, and provisional kilogram standards were manufactured and distributed to the 559 districts of the French Republic. A botanist named Dambey embarked on a trip to the United States with a copy of the provisional meter and kilogram standards. However, the ship he was on was attacked by pirates in the Caribbean and he was either captured or killed. The standards he carried were lost and have never been found. 1799 Delambre and Méchain presented their survey results, which were accepted at an international conference. Metric standards were fabricated and certified. Delambre and Méchain completed their work in surveying a meridian using triangulation methods from Dunkerque to Barcelone and their work was accepted at an international conference (conseil des Cinq Cents et au Conseil des Anciens) after compromises were made regarding the ellipticity of the Earth. The Earth's ellipticity actually causes an arc minute of latitude to represent a gradually changing distance when proceeding north or south. A mean value had to be derived and the amount of ellipticity used in that calculation has a very small effect, but one that precise metrologists care about. Delambre and Méchain deduced an ellipticity of 1/150 and this was combined with the results of a survey conducted in Peru between 1736 and 1740 to settle on an accepted value of 1/334. Ever since this date the meter has remained the same size. Different methods of defining the standard have evolved; these have served only to make the standard for the meter more precise and have not changed its length. A new standard meter bar ("le mètre étalon" or "the archive meter") was made of platinum, based on this survey, to represent ("realize", in metrology terms) the standard meter. This and the new standard kilogram were fabricated by Etienne Lenoir (a maker of astronomical instruments and also the provisional meter and kilogram standards mentioned above) and, after certification, deposited in the Archives of the Republic (Archives de la République) on 1799 June 22. Copies of these would later be given to the United States. To amplify a bit, The original intent was to make the meter's definition standard so that anyone on Earth could construct their own reference bar from their own surveys of the Earth at any longitude. Amazingly, it had already been postulated by Isaac Newton et al. for a century or so that the Earth was in fact NOT a regular ellipsoid of revolution but was in fact "lumpy" with "high" regions and "low" regions. In other words, scientists had good reason even in 1790 that no two lines of longitude are necessarily the same length. The D-M survey was thus to some extent a fool's errand. Likewise the problems experienced in the southern part of the survey, getting observation triangles to close, due to the mass of mountains throwing off determination of the local vertical had also been predicted. At least the D-M survey helped to bolster those century-old predictions. Briefly, the meter used today is the same as the 1799 meter to the extent that each new definition maintained its size within the limits of the uncertainty at each stage. Any inadvertent change in size over the last 200 years is certainly smaller than the change in the U.S. yard "on purpose" in 1959. Jim On 2010-10-18 1416, Pat Naughtin wrote: > Dear All, > > From time to time I read the line (in various sources) that goes > something like: > > /*The metre has never changed in length, only the definition has been > rewritten to provide better accuracy and precision.*/ > > This poses the question, "Which is the metre we use?" > > A brief chronology goes like this: > > 1790 May 8 The French National Assembly decides that the length of the > metre will be equal to the length of a pendulum with a half-period of > one second. > > 1791 March 30 Recognising that a universal standard of measurement was > needed, the French National Assembly accepted the proposal by the French > Academy of Sciences that the new definition for the metre be equal to > one ten-millionth of the length of the Earth's meridian along a quadrant > of the Earth, that is the distance from the equator to the north pole. > To determine this length about one tenth of the Earth's circumference, > from Dunkirk, in France, to Barcelona, in Spain, was meticulously > measured. Due to lack of knowledge of the true shape of the Earth, this > definition was never implemented. > > *1795 A provisional metre bar was constructed of brass.* > > 1799 December 10 The French National Assembly specifies a platinum metre > bar deposited in the National Archives, as the final standard of length > for the whole world.A platinum rod was produced in Paris that was > exactly one metre from end to end. This became the master standard for > the whole world's measuring system. Known as the /'Mètre des Archives'/ > it became the "/universal measure/" that is the basis for the metric > system we now all use. > > From this it looks like the pendulum was never officially recognised > and neither was the metre derived from this measurement of the Earth. > Does this mean that the length of the 1795 brass bar is still the world > standard for the length of a metre assuming that it is true all > subsequent definitions of the metre have kept this same length (as the > 1795 brass bar) while only the words of the definitions changed to > achieve greater accuracy and precision. > > Am I misreading this history? Is the 1799 platinum bar the one that > takes precedence? > > Cheers, > Pat Naughtin > Author of the ebook, /Metrication Leaders Guide,/ see > http://metricationmatters.com/MetricationLeadersGuideInfo.html > Hear Pat speak at: http://www.youtube.com/watch?v=_lshRAPvPZY > PO Box 305 Belmont 3216, > Geelong, Australia > Phone: 61 3 5241 2008 > > Metric system consultant, writer, and speaker, Pat Naughtin, has helped > thousands of people and hundreds of companies upgrade to the modern > metric system smoothly, quickly, and so economically that they now save > thousands each year when buying, processing, or selling for their > businesses. Pat provides services and resources for many different > trades, crafts, and professions for commercial, industrial and > government metrication leaders in Asia, Europe, and in the USA. Pat's > clients include the Australian Government, Google, NASA, NIST, and the > metric associations of Canada, the UK, and the USA. See > http://www.metricationmatters.com > <http://www.metricationmatters.com/>for more metrication information, > contact Pat at [email protected] > <mailto:[email protected]> or to get the free > '/Metrication matters/' newsletter go to: > http://www.metricationmatters.com/newsletter to subscribe. > -- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
