Harrison's marine chronometer H1

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Essential information

Opening times: 
Royal Observatory, Meridian Line and Historic Royal Observatory, Flamsteed House, Time & Longitude gallery

Find the timekeeper that changed navigation forever and would lead to the solving of the problem of longitude.

This is the first experimental marine timekeeper made by John Harrison in Barrow-on-Humber between 1730 and 1735 as a first step towards solving the longitude problem and securing the great £20,000 prize offered by the British government.

Now known as 'H1', the clock is unaffected by the motion of a ship owing to its two interconnected swinging balances.

It compensates for changes in temperature and, thanks to extensive anti-friction devices, runs without any lubrication.

It was the first relatively successful marine timekeeper of any kind and was the toast of London when Harrison unveiled it in 1735.

It is one of the great milestones in clock-making history.