John Harrison – Clockmaker

John Harrison (1693-1776)  and his brother James were introduced to clock repair by their father, Henry. Clock making, or horology, was undergoing a developmental revolution. Mechanical clocks had existed since the fourteenth century. They remained rather primitive in their operation until Christiaan Huygens invented the weight-and-pendulum clock in 1656.

Self-taught individuals, John and James were also introduced to carpentry and surveying by their father. They chose, however, to become totally involved in making clocks, and almost immediately began developing their own improvements to them. One such innovation was the gridiron pendulum, which consisted ofa grid of iron and brass that compensated for changes in temperature.

Perhaps the major problem with clocks in those days was that they were totally dependent upon the earth’s gravity for their operation. This meant that they could not keep accurate time at sea, and could not be adapted for portability. Even moving them across a room would require adjustment.

The Harrison brothers set to work on developing a marine chronometer in 1728. The motivating factor was money. In 1714, the English Admiralty set up an award of £20,000 for anyone who could provide mariners with a reliable clock that, when used with celestial sightings, could keep them informed of their longitude at sea. Mariners had to rely heavily on dead reckoning to find their way, often leading to tragic results.

The Harrisons made several models of marine chronometers. The fourth model proved to be the most successful. On a nine-week voyage from England to Jamaicain 1761, the device had only a five-second error. The Harrison strategy was to design an instrument that was not only internally accurate but also externally stable.

The Board of Longitude, apparently miffed that a common artisan had achieved the coveted goal, reluctantly gave up only half of the prize. John, minus his brother, went on to get what was justly due him.

The Board subjected his invention to undue scrutiny and required him to design a fifth model. This time, Harrison out did himself by designing a compact timepiece that resembled a modern day pocket watch. It was far more convenient than the previous models, which were heavy and bulky. The Board still refused to capitulate. It finally took a personal appeal to King George III to set things right. The King intervened, and Harrison finally received the full reward in 1773 at age seventy-nine. Harrison lived only three more years. England and the world benefitted greatly from the persistence of Harrison, whose love for his work kept him going despite the many years of frustration he suffered.

via John Harrison Biography (1693-1776).

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