Quick Facts
Born:
Sept. 1717, Exeter, Devon, Eng.
Died:
Nov. 14, 1794, Newington Place, Surrey (aged 77)

Thomas Mudge (born Sept. 1717, Exeter, Devon, Eng.—died Nov. 14, 1794, Newington Place, Surrey) was considered England’s greatest watchmaker, who was the inventor of the lever escapement, the most dependable and widely used device for regulating the movement of the spring-driven watch.

Mudge served as apprentice to the watchmaker George Graham before opening his own a shop a few doors away in Fleet Street in 1750. The quality of Mudge’s work brought him commissions from Ferdinand VI of Spain, the engineer John Smeaton, and other influential persons throughout Europe. He invented the lever escapement about 1755, introducing it on a smaller scale in a watch that he made in 1770 for King George III, then given to Queen Charlotte of England.

In 1771 he retired from business and turned his attention to the improvement of marine timekeepers. He achieved some success by refinement of detail and by somewhat complicating the mechanism but made no basic advance. He sent his first chronometer for trials at the Royal Greenwich Observatory in 1774 and again in 1776–77. During the second trial its performance was so good that it was not equaled by other chronometers at Greenwich for nearly a century, but his son’s attempts to establish a factory to produce his father’s timekeepers ended in failure.

Jonathan D. Betts

chronometer, portable timekeeping device of great accuracy, particularly one used for determining longitude at sea.

Although there were a couple of earlier isolated uses, the word was originally employed in 1779 by the English clock maker John Arnold to describe his sensationally accurate pocket chronometer “no. 1/36.” Ordinary clocks were of no use at sea due to temperature changes and the ship’s motion. It was not until the 18th century that John Harrison, a self-taught English carpenter, invented and constructed four marine timekeepers, the fourth of which effectively won him the reward of £20,000 offered in 1714 by the British government for any means of determining a ship’s longitude within 30 geographical miles (about 34.6 miles, or 55.7 km) at the end of a six weeks’ voyage. (The geographical mile is defined as one minute of arc along the Earth’s equator; compare the nautical mile, defined as one minute of arc along any great circle route.) A timekeeper fulfilling this condition would have to keep time within three seconds per day, a standard that, at the date the reward was offered, had not been attained by the best pendulum clocks on shore. Though Harrison’s original invention was complicated, delicate, and costly, his successful design led to further investigations by others and eventually to the modern marine chronometer.

The modern chronometer is, broadly speaking, a large, well-made watch but with a detached chronometer escapement, suspended in gimbals (a set of rings connected by bearings) poised so as to remain horizontal whatever the inclination of the ship. It is thus safeguarded from those alterations of position that slightly affect the timekeeping of even the best watches. In addition, it differs somewhat in its mechanism from the ordinary watch, the spiral balance spring and lever escapement of the latter being replaced by a helical balance spring and a spring detent, or chronometer escapement. In a chronometer this form of escapement is mechanically superior to any other and requires no oiling other than at the pivots, but it is not suitable for use in pocket watches, because it is very fragile and also, if given a more or less circular twist, may “trip,” causing a rapid gain. For the purpose of equalizing the force of the mainspring, almost all chronometers are fitted with a fusee (a cone-shaped grooved pulley) and a chronometer compensation balance, by which the effects of heat and cold upon the timekeeping are practically nullified. By these devices the chronometer usually provides timekeeping accurate to within 0.5 second per day.

barometer. Antique Barometer with readout. Technology measurement, mathematics, measure atmospheric pressure
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Jonathan D. Betts