John Arnold’s son


John Arnold's son, John Roger Arnold, was born on 13 February 1769. At the age of 14, he was apprenticed to his father before departing for Paris at the age of twenty-three to complete his training under the tutelage of the famous Abraham-Louis Breguet.

Discreet and industrious, John Roger shared his father's exceptional watchmaking skills, proving his worthy successor and collaborating with him from 1796 onwards. He made far more marine and pocket chronometers than his father, and their quality was in every respect equal to those of John Arnold.

He also invented some outstanding innovations, including a U-shaped balance, which he patented in 1821, and, more importantly, a keyless winding system, developed with his foreman Thomas Prest and patented in 1820, 25 years prior to that of Adrien Philippe.

He also developed the very classic design of his father's watches, and even conceived new and original models. His inventions include jump-hour marine chronometers and pocket chronometers featuring a regulator dial, large central seconds hand and, in some cases, a balance that was visible through the dial.

In 1830, after the demise of his adopted son, he went into partnership with the brilliant watchmaker Edward John Dent. The watches and chronometers produced by Arnold and Dent went on to enjoy universal renown:

"The mercury compensation clock by Arnold and Dent also displays a very pleasing running smoothness. The clock was cleaned by Mr Baridon in April 1846. Since then, its diurnal rate has slowed slightly, causing it to lose time over several months. The time loss started at zero and increased very gradually to 1.5 seconds in March 1847, subsequently decreasing by a tenth of a second from one day to the next, an amount which, in general, hardly varied."

"Of all the watches we have examined, the one verging on perfection is, without dispute, No. 1078 by Arnold and Dent. Its rate remained extremely regular over more than two consecutive years, both in France and the West Indies. Moreover, this watch possesses the inestimable advantage of running for 50 consecutive hours if required, and never once stopped during its campaign on theDaphne, even though the crew forgot to wind it several times."

John Roger and Edward John, both passionate about chronometry, went on to make remarkable discoveries regarding the influence of magnetism and temperature on chronometer rates. A particularly important innovation was the manufacture of exceptional chronometers with glass balance springs and spirals; the sensational forerunners of contemporary silicon escapements:

"Having compared the rate of a chronometer fitted with a glass spring with that of other chronometers fitted with springs made of various metals when subjected to a temperature increase of 32° to 120°F, we observed that the first lost just 40 seconds over 24 hours, while a chronometer with a gold spring lost 8 minutes and 4 seconds, one with a steel spring lost 6 minutes and 25 seconds and one with a palladium spring lost 2 minutes and 31 seconds.

Messrs Arnold and Dent attribute these differences principally to varying degrees of elasticity reduction of these diverse substances as a result of the temperature increase. Having ascertained that glass loses far less elasticity as a result of this than metals, they proceeded to create a glass spring, which permits the correction of this slight error, using a glass disc for this purpose. After the compensation was complete, they realized that the isochronism of the glass spring was as perfect as that of its metal counterpart. Chronometers fitted with glass springs compensated in this manner are currently on trial at the Royal Observatory."

The partnership with Dent ended in 1840. John Roger Arnold, by then an old man, continued to pursue his passion until his death. Another excellent watchmaker, Charles Frodsham, took over the helm after Arnold's demise.



Bajot, M.,Annales maritimes et coloniales,vol. 1 (Paris, 1842).

Bibliothèque Universelle de Genève, vol. 5 (Geneva, 1836).

University of Geneva,Archives des sciences physiques et naturelles,vol. 11 (Geneva, 1849).


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