Marine Chronometer

This device, an accurate clock that works on ships, allows sailors to much more accurately navigate. Before this innovation, sailors had to guess, and it was common for ships to miss their destination on a journey by hundreds of miles. This device reduced the risk and cost of long journeys by ship, lowering the cost of long-distance trade. Modern GPS also relies on extremely accurate timers.


Sun and star positioning allowed ships to determine latitude with reasonable accuracy but not longitude. Before the marine chronometer, the only way to determine longitude required a highly accurate clock. Except that the only clicks in existence relied on pendulums, which do not work at sea. Due to this, sailors often veered off course by a long distance. It was not unheard of to sail to the wrong country, which might be at war with a ships intended destination.

In one notable accident, the Scilly Naval Disaster of 1707, England lost four ships and 1,400-2,000 men after a longitude navigation error. After that, the English parliament floated a £20,000 prize (an enormous amount of money) to anybody who could make an accurate clock that worked at sea.

Pushback From Professionals

Harrison, a self-educated clockmaker, built a spring-loaded clock that enabled sailors to accurately determine the longitude making navigation more precise and safer. Harrison built four versions, H1-H5[1], over 46 years. Harrison’s clock was so accurate and reliable that even the earliest prototype continues working today:

Despite that Harrison’s clock repeatedly passed tests, aristocratic judges rejected it. The judges were members of an exclusive click making society, Worshipful Company of Clockmakers. As a self-taught inventor, Harrison did not belong and they argued his clock failed to meet their criteria. Modern engineers have determined these rejections were in bad-faith: that Harrison’s clock worked.

Capt. James Cook attributed his ability to circumnavigate the globe to Harrison’s H4 clock. Despite this, the clockmaking judge panel refused to agree the clock was good enough. Eventually, a portion of the prize was paid as outraged legislators and King George III intervened, but Harrison was never awarded the entire prize.

[1] H1-H3 were large spring clocks; pendulum style clocks that used springs. H4-5 were timepieces.