H4

Marine timekeeper, H4. This is Harrison's prize-winning longitude watch, completed in 1759. Harrison had been working on improving watches as a sideline to his development of the much larger H3. In 1753 a pocket watch was made to Harrison's design by watchmaker John Jefferys. This went so well that Harrison began to realise that it pointed to the longitude solution - not in H3 but in smaller watches. Work began on H4 in 1755 and, with its very stable, high frequency balance, it proved the successful design. It is shown here at almost actual size. See also; ZAA0034 (H1), ZAA0035 (H2) and ZAA0036 (H3).
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