John Arnold was born in Bodmin in 1736, the son of a watchmaker. He began young as an apprentice to his father and went on to become a partner. However, an argument saw the ending of their partnership and young Arnold left the country initially to work in The Hague, Holland.
In 1756 John Arnold returned to Britain, this time to London where he set up a chronometer factory at Chigwell. As his skills grew, so did his reputation as a fine watchmaker, particularly of smaller time pieces. As well as watchmaking skills Arnold was also blessed with a good deal of business and social acumen. In 1764 he constructed the smallest ever repeating and striking watch, which was set into a ring and presented to King George III as a gift.
John Arnold next turned his attention to the manufacture of more accurate timepieces and invented one of such quality and reliability that Captain James Cook used it on his South Sea Voyages 1772 1775. One of the most innovative design features was the temperature compensation using a bi-metallic strip. He also solved the problem of friction in the balance spring.
His son John Roger Arnold was born in 1769 and was apprenticed to both his father and with A-L Bregue. In 1787 they founded the firm of J. Arnold & Son, the name of which still survives as a manufacturer of precision watches and chronometers. In 1788 they produced the first pocket chronometer which so impressed the Astronomer Royal that he decided to test it himself at Greenwich . The watch, no. 1/36 went so well in trials that he decided to give it a new name, that of chronometer and was thus the first person to use that term in its modern sense.
With the world opening up through exploration a solution to the problem of calculating longitude aboard ships was the scientific quest of the day. The solution lay in accurate chronometers. The first seaworthy chronometers were created by another Englishman, John Harrison. But it was Thomas Earnshaw and John Arnold who really perfected the design. The two were fierce competitors and there was great controversy about Arnolds contribution to the solution and his work was only recognized by the Board of Longitude after his death, when in 1805 his son was awarded the sum of £3000.The story of this is told in Dava Sobel's historical account, Longitude.
John Arnold died in 1799 at the age of 63 and is buried in Chislehurst, Kent. His son John Roger continued the business after his death with John Dent. He also went on to become Master of the Clockmaker’s Company in London in 1817.
In Bodmin, where Arnold originally worked is named Arnold´s Passage. It is to be found just off Fore Street and a commemorative plaquemarks the spot