[LEAPSECS] Marine chronometers, was Re: A new use for Pre-1972 UTC

[Tony Finch]

On Tue, 17 Feb 2009, Joseph M Gwinn wrote:

>

> > The navigators who used marine chonometers knew perfectly well that

> > those chronometers did not keep the "right" time as measured by clocks

> > on land being reset by telescopes.  Instead they knew that if their

> > chronmeters were treated well they kept uniform time, and those

> > navigators knew that getting the "right" time meant keeping a log of

> > the difference between the "right" time of the clocks on land and

> > their chronometer.

>

> They used the best cronometers then available.  Harrison's first attempt

> at a chronometer was in 1730, and success came many years later, in 1760

> or so.


Steve is right. The key difference between H4 and Harrison's previous
clocks is that he gave up trying to make a clock that keeps correct tims
and instead designed a clock that kept uniform time, which he could
calibrate before a journey. This is often not well explained in the potted
histories.

Tony.
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