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    Re: Leap seconds at Big Ben.
    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{at}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---.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/
    ===============================================================================
    
    
    
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