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.
Bibliography:
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).
