John Harrison

John Harrison (1693–1776) was a self-taught English carpenter and clockmaker who 

revolutionized maritime navigation by inventing the marine chronometer. His invention solved the "longitude problem," which had previously led to numerous shipwrecks and thousands of deaths because sailors could not accurately determine their east-west position at sea. 

Key Accomplishments and Innovations

• The Longitude Prize: After the Scilly naval disaster of 1707, the British Parliament passed the 1714 Longitude Act, offering a £20,000 reward (roughly £3.97 million today) for a method to determine longitude to within half a degree.

• Marine Chronometers (H1–H5): Harrison spent decades developing five main timekeepers.

  • H1 (1735): His first attempt, a large brass machine using interlinked swinging balance beams to counteract ship motion.

  • H2 and H3: Subsequent versions that introduced groundbreaking features like the bimetallic strip (for temperature compensation) and caged roller bearings.

  • H4 (1759): His masterpiece, which looked like a large pocket watch rather than a bulky clock. It proved highly accurate on a voyage to Jamaica, losing only 5 seconds over 81 days.

  • H5: A refined version of H4 that was personally tested by King George III.

• Inventions: He created the grasshopper escapement, a low-friction mechanism that required no lubrication, and the gridiron pendulum to prevent thermal expansion in clocks. 

The Dispute and Legacy

Despite meeting the prize requirements, the Board of Longitude—which favored astronomical methods like "Lunar Distances"—was reluctant to pay Harrison in full. It was only after appealing directly to King George III in 1773 that the 80-year-old Harrison received the remainder of his reward from Parliament. 

Today, Harrison is recognized as a pioneer who made global trade and exploration safer. His original timekeepers are on display at the Royal Observatory in Greenwich. In 2015, a modern version of his "Clock B" design was officially certified by Guinness World Records as the most accurate mechanical pendulum clock in the world.