Longitude 3 - The winner

© National Maritime Museum, Greenwich, London

Harrison's famous H1 Sea Clock, his first attempt. It took him five years to design and build. Later he realised that large clocks were not the right way. Smaller watches worked better because the timing movements were much faster than the ship's movement and the two did not interfere. After 30 years he had his final solution and collected the prize.

© National Maritime Museum, Greenwich, London

This sea watch is a copy of Harrison's H4 by Larcum Kendal called the K1. The Board of Longitude insisted that designs were to be available to other makers to allow more innovation and to keep the price down. This one only cost £450 (around £34,000 today)

The memorial to John Harrison at Westminster Abbey. The line is 00º07'35'' W of Greenwich - not very far.

Solving the problem- clocks and stars


1. Clocks and pocket watches were made before 1714. What conditions would you expect at sea in a wood sailing ship? Would these be harmful to clocks and watches?

2. Astronomical observations can be used to measure time, for example the timing of the orbits of the moons of Jupiter. Why would making those observations be difficult at sea?

3. In the eighteenth century, ships navigators were highly skilled in mathematics and astronomy. They were also all men. In the modern services are science skills still needed and are women likely to be equal to men in these skills?



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A solution to the longitude problem that had evaded the leading scientists and astronomers of the day was eventually solved by John Harrison, a carpenter and clockmaker born near Wakefield in Yorkshire.
John Harrison worked on the problem for over thirty years.

© National Maritime Museum, Greenwich, London

Harrison's H4 sea watch

© National Maritime Museum, Greenwich, London
Finding longitude was not all about clocks. Captain Cook made successful use of astronomical tables and accurate observations. On later voyages he used Harrison's marine watches.

Credit: NASA
Today's explorers are also scientists. This is another captain, Samantha Cristoforetti, a Captain in the Italian Air Force, running experiments on board the International Space Station in April 2015.