John Harrison's extremely accurate 18th century clock

I love the story of John Harrison, as told (in simplified form) in the book Longitude. Harrison was a self-educated clockmaker who invented an accurate clock that would work on a ship and allow longitude to be calculated. This was well before GPS, at a time when Britain and other nations were venturing out into the world by sea without the ability to accurately find their position. 

Harrison did a significant amount of work towards solving the problem and received a reward from the Longitude Act.

It seems that he also created a design for a clock more accurate than anything else at the time. Finally, after 250 years this clock was built, tested and found to be as accurate as expected.

The story of Harrison is quite interesting in that he devoted his life to solving the problem of creating an accurate nautical clock, actually succeed and received the recognition he deserved, during his lifetime.