Marine Chronometer - History - The Modern Chronometer

The Modern Chronometer

About the same time in France, Pierre Le Roy invented in 1748 the detent escapement characteristic of modern chronometers. In 1766, Pierre Le Roy created a revolutionary chronometer that incorporated a detent escapement, the temperature-compensated balance and the isochronous balance spring: Harrison showed the possibility of having a reliable chronometer at sea, but these developments by Le Roy are considered by Rupert Gould to be the foundation of the modern chronometer. The innovations of Le Roy made the chronometer a much more accurate piece than had been anticipated.

Ferdinand Berthoud in France, as well as Thomas Mudge in Britain also successfully produced marine timekeepers. Although none were simple, they proved that Harrison's design was not the only answer to the problem. The greatest strides toward practicality came at the hands of Thomas Earnshaw and John Arnold, who in 1780 developed and patented simplified, detached, "spring detent" escapements, moved the temperature compensation to the balance, and improved the design and manufacturing of balance springs. This combination of innovations served as the basis of marine chronometers until the electronic era.

The new technology was initially so expensive that not all ships carried chronometers, as illustrated by the fateful last journey of the East Indiaman Arniston. However by 1825, the Royal Navy had begun routinely supplying its vessels with chronometers.

It was common for ships at the time to observe a time ball, such as the one at Greenwich, to check their chronometers before departing on a long voyage. Every day, ships would anchor briefly in the River Thames at Greenwich, waiting for the ball at the observatory to drop at precisely 1pm. This practice was responsible for the subsequent adoption of Greenwich Mean Time as an international standard. (Time balls became redundant around 1920 with the introduction of radio time signals, which have themselves largely been superseded by GPS time.) In addition to setting their time before departing on a voyage, ship chronometers were also routinely checked for accuracy while at sea by carrying out lunar or solar observations.

Although industrial production methods began revolutionizing watchmaking in the middle of the 19th century, chronometer manufacture remained craft-based much longer. Around the turn of the 19th to 20th century, Swiss makers such as Ulysse Nardin made great strides toward incorporating modern production methods and using fully interchangeable parts, but it was only with the onset of World War II that the Hamilton Watch Company in the United States perfected the process of mass production, which enabled them to produce thousands of their superb Hamilton Model 21 & Hamilton Model 22 chronometers of World War Two for the United States Navy & Army and other Allied navies. Despite Hamilton's success, chronometers made in the old way never disappeared from the marketplace during the era of mechanical timekeepers. Mercer of St. Albans in Britain, for instance, continued to produce high-quality chronometers by traditional production methods well into the 1970s.

Without their accuracy and the accuracy of the feats of navigation that marine chronometers enabled, it is quite likely that the ascendancy of the Royal Navy, and by extension that of the British Empire, would not have occurred; the formation of the empire by wars and conquests of colonies abroad took place in a period in which British vessels had reliable navigation due to the chronometer, while their Portuguese, Dutch, and French opponents did not. For example: the French were well established in India and other places before Britain, but were defeated by naval forces in the Seven Years' War.

The most complete international collection of marine chronometers, including Harrison's H1 to H4, is at the National Maritime Museum, Greenwich, Britain.