What was the name of the first device that could tell the right time at sea (accurate enough)?

John Harrison's H-4 clock (ca. 1759), which met the criteria of accuracy set forth by Britain's Board of Longitude.

There's a fascinating book on this subject: Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time by Dava Sobel.

[I originally answered H-3, but on review I think it was the H-4 model that won the prize.]

Good answer, Professor, the H4 timepiece, and thanks for the link.

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