The Wikipedia article on pendulums gives a pretty good time line. http://en.wikipedia.org/wiki/Pendulum I think the dependence on local gravity would have made it a poor standard, and not that portable. The gravity dependence (and the earth's oblateness) was understood (even if not well measured) by 1680.
--- On Mon, 9/28/09, Pat Naughtin <[email protected]> wrote: From: Pat Naughtin <[email protected]> Subject: [USMA:45918] The plummet in metric history To: "U.S. Metric Association" <[email protected]> Date: Monday, September 28, 2009, 7:14 PM Dear All, Does anyone know anything of the history of the 'plummet'? Apparently the plummet was used in Wellington's armies as an instrument to measure the rate at which soldiers marched. The plummet was a piece of cord attached to a lead shot that was then used as a pendulum. Some approximate values are: 1000 mm plummet was used for 60 steps per minute 600 mm plummet was used for 75 steps per minute 300 mm plummet was used for 108 steps per minute 250 mm plummet was used for 120 steps per minute (The last of these is probably the most common rate used by military services today) As the plummet was in common use in 1812, my question relates to how long before 1812, this pendulum method was in use for military marching. If this technique was available in 1790, for example, then it would have had a significant influence on the metric debate about whether to use the plummet pendulum or the size of the meridian as the basis for the length of the metre. This debate centred around Borda who wanted to market his 'repeating circle' and Thomas Jefferson who favored the pendulum method because of its universal availability and its portability; sadly perhaps, Borda won that round! See http://www.gap-system.org/~history/Biographies/Borda.html where you will find: When Borda was made Chairman of the Commission of Weights and Measures, which had as its members Condorcet, Lavoisier, Laplace and Legendre, he soon put his accurate surveying instrument to good use. The Commission was set up in 1790 to bring in a uniform system of measurement. It considered a proposal which had already been made to the French government to base the metre on the length of a pendulum which beat at the rate of one second. This proposal had found favour with Britain and the United States who considered it a truly international measure. Borda, however, reported on the 19 March 1791 that the Commission had decided on a different standard, namely that one metre should be one ten millionth of the distance from the North Pole to the equator. His argument against the pendulum standard was that it based one unit on another, which might itself change, and also that the second itself was an arbitrary unit based on the division of a day by 12 × 60 × 60. Borda argued that the day should be divided into 10 hours with an hour divided into 100 minutes each of 100 seconds. Under Borda's leadership the project to accurately measure the distance from the North Pole to the equator using the Borda repeating circle was carried out. Cheers, Pat Naughtin Author of the ebook, Metrication Leaders Guide, that you can obtain from http://metricationmatters.com/MetricationLeadersGuideInfo.html 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 for more metrication information, contact Pat at [email protected] or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
