Encyclopedia > John Harrison

  Article Content

John Harrison

John Harrison (1693 - 1776) was an English carpenter[?] by initial trade, who in his spare time built and repaired clocks. He was born at Foulby in Yorkshire, the eldest son of a carpenter. Legend has it that he was given a watch when he was six to amuse him while in bed with smallpox, spending hours listening to it and studying its moving parts. Scholars today, however, consider this unlikely to be true, as clocks and watches of all kinds were rare and expensive at the time, and Harrison came from a family of fairly modest means.

He was a man of many skills and used these to improve on the way clocks were built. For example, he developed the gridiron pendulum, consisting of alternating brass and steel rods assembled so that the different expansion and contraction rates cancelled each other out. Another example of his inventive genius was the grasshopper escapement[?] -- a control device for the step-by-step release of a clock's driving power. Being almost frictionless, it required no oiling.

In 1728 Harrison packed up full scale models of his inventions and drawings for a proposed marine clock to compete for the Longitude Prize and headed for London seeking financial assistance. He was sent to George Graham[?], the country's foremost horologist[?]. He must have been impressed with Harrison for Graham personally loaned him money and told him to build a model of his marine clock.

It took Harrison seven years to build Harrison Number One or H1. This was approved by the Board of Longitude for sea trials and Harrison moved on to develop a sea capable version H2. However, England was at war with Spain at the time and the mechanism was deemed too important to risk it falling into Spanish hands. Seventeen years after H2, Harrison completed H3. All of these early designs were heavy instruments needing to be slung from a beam in a ship and all were designed to keep time in a ship rolling and pitching in the worst storm. H4 was an instrument of beauty being of the shape of a large pocketwatch[?]. This trial was completely successful but judged by the board to be a fluke. A second test was also successful but still the board were reluctant to accept the conditions had been met. The board imposed significant restrictions on Harrison, demanding that he hand over all four instruments and make a further copy of H4.

Harrison felt "extremely ill used by the gentlemen who I might have expected better treatment from" and decided to enlist the aid of King George III. He asked for and was granted an audience with the King who became extremely annoyed with the Board. King George tested No. 5 himself at the palace and when it had lost only four and a half seconds in ten days he told Harrison to petition Parliament for the full prize. So in 1773, Harrison finally received his reward.

See also chronometer, time

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article
Islandia, New York

... all households are made up of individuals and 2.3% have someone living alone who is 65 years of age or older. The average household size is 3.04 and the average family ...

This page was created in 33.6 ms