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Re: Leap seconds at Big Ben.
From: Richard B. Langley
Date: 2009 Jan 1, 16:42 -0400
From: Richard B. Langley
Date: 2009 Jan 1, 16:42 -0400
George's posting gives me a reason to highlight another connection of Fredericton to navigation and time keeping. A prototype of the Great Clock at Westminster (usually referred to as Big Ben, although that was the name given to the great bell that chimes the hours) was installed in Christ Church Cathedral, Fredericton, in 1854, by the firm of Denison. Big Ben began operation on 31 May, 1859. This year marks its 150th anniversary. If you're interested in the history of Big Ben, you might try to track down the slim 1946 book "The Book of Big Ben: The Story of the Great Clock of Westminster" by Alfred Gillgrass (Citizen and Liveryman, The Worshipful Company of Clockmakers, London) and with a foreward by Lt.-Cmdr. Rupert T. Gould (who restored the marine chronometers of John Harrison). -- Richard Langley Quoting George Huxtable: > > A bit more information about leap seconds, for anyone who happens to be > interested. > > The chimes of Big Ben, from London, ring in the New Year, via radio and TV, > all over Britain, and over much of the Western World that has so far escaped > the dominion of the USA. The clock dates from nearly 150 years ago, the work > of Nicholas Denison. > > Those responsible for the mechanism have the task of introducing a leap > second, for which the mechanism was never designed. It wouldn't do to have > the bells ring out a second before the due moment of New Year. My wife Joan, > who takes an interest in such matters as her birthday is on New Year's Day, > heard a news item on the radio about how the job is done, and has passed the > information on. > > There is no seconds-hand on the clock, but presumably there must be an > internal cam-wheel, turning as a seconds-hand would, to trigger the strike. > The pendulum, nearly 4 metres long beats at 2-second intervals, a cycle > taking 4 seconds, so that wheel would step at 2-second intervals. > > It wasn't made clear exactly how long before the moment of New Year the > adjustment process for the leap-second commences, but the job has to be done > gradually, as the required step-change is impossible. To adjust the rate, > weights are added or subtracted from a tray that's attached to the pendulum. > Traditionally, these have been (old) pennies, copper coins valued at a bit > less han half of one (new) pence. This allows the clock to run a bit more > slowly as the leap-second moment is approached, so that at New Year, it > strikes correctly, allowing for the leap-second, and the rate of going can > then be returned to normal. That must mean that during the adjustment > period, the clock must be increasingly slow on UT, by up to ! second. > Presumably, that will affect the strikings (at the quarter-hours) that > precede midnight. > > A happy New Year to all, > > from George. > > contact George Huxtable, at george@hux.me.uk > or at +44 1865 820222 (from UK, 01865 820222) > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. > > > > > =============================================================================== Richard B. Langley E-mail: lang@unb.ca Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ =============================================================================== --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---