Famous Watchmakers | XVII | John Harrison | Fondation De La Haute Horlogerie

Century

John Harrison

John Harrison © MHE

1693-1776
English clockmaker and chronometer maker.
Self-taught.

1720's
Applied the grid compensation on clocks (grid pendulum). The grid pendulum used two metals (steel and brass) which dilate under the effects of varying temperature. It was an alternative to George Graham's mercury pendulum until the development of the invar by Charles Edouard Guillaume in 1895.
He invented the “grasshopper” escapement, a new form of deadbeat escapement for clocks. Difficult to set, it was not often used, except by John Harrison himself. It worked with great amplitudes (subject to circular error) and was combined with an equality winder (system guaranteeing constant force).

Circa 1728
John Harrison submitted his inventions (grid pendulum and “grasshopper escapement”) with a marine chronometer.
John Harrison's first marine chronometer, called H 1 was completed in 1735.

1749
Golden medal awarded by the Royal Society.

1761
Invented a system to compensate for the effects of temperature variation (Harrison compensation): used bi-metallic blades to control the active length of the spiral.

1761-1764
After years of research, Harrison tested his H4 chronometer in sea trials, first in 1761 and again in 1764. Its accuracy exceeded that required by the numerous competitions which, since the late sixteenth century, promised a reward to whomever solved the so-called "longitude problem."

1762 - 1765 - 1773
Rewarded by the English Parliament for having solved the problem of longitude.
Received two instalments (1762 and 1765) after tests on his fourth chronometer, called H 4 and the balance (1773) after having produced a fifth and last chronometer.