Completed in 1781, the John Arnold pocketwatch numbered 23/78 is
unique for a number of reasons. It features several inventions by
John Arnold and other outstanding features including a pivoted
detent escapement with a "double S" balance, a cylindrical balance
spring, and a clever temperature compensation mechanism.
Furthermore, it is the only known example to have survived in
its exact original condition without ever having undergone any
restoration, with all parts including the silver case, enamel dial
and movement perfectly intact and untouched.
This extraordinary result achieved at Sotheby's auction is an
attestation to the pivotal role John Arnold played in advancing
John Arnold rapidly established a reputation for outstanding
mechanical expertise and was the first watchmaker to produce a
jewelled ruby cylinder escapement. He showcased this in an
exceptionally small half-quarter repeating watch mounted in a ring,
which he offered to King George III. His growing fame attracted an
affluent clientele. He could easily have lived comfortably, making
exquisite repeating watches and calendar watches. But John Arnold
was relentlessly driven by the greatest watchmaking challenge of
his age: to build a timepiece that would enable ships to navigate
safely, transform science and roll back the boundaries in
astronomy. That challenge was precision, and Arnold made it his
Between 1770 and 1790, he painstakingly refined the art of
watchmaking, introducing decisive improvements that heralded the
arrival of chronometry. It is to him we owe a series of
trailblazing inventions that included a detent escapement, a
helical balance spring, terminal curves that make the helical
balance spring isochronous, the first-ever use of gold for balance
springs, and a range of bimetallic balances that offset errors
caused by temperature fluctuations.
Arnold's chronometers were used by some of the greatest
explorers and navigators of his time on their epic voyages. His
regulators and their continual refinement bear witness to the
colossal progress of science and astronomy across Europe.
Arnold was also heir to a series of exceptional English
watchmakers, each of whom advanced the art of watchmaking in his
own way: George Graham, Thomas Tompion, Thomas Mudge and John
Harrison. Arnold, however, was the first to usher watchmaking into
the modern era by designing high-precision, reliable watches that
were also relatively easy to manufacture. In its report on Arnold's
pocket chronometer No. 2 in 1780, the Board of Longitude had this
"So far as this watch has been tried, it must be acknowledged by
all, that it is superior to every one that had been made before it.
Nothing therefore seems to remain but for … Mr. Arnold … to make
other watches … to entitle him to the second reward offered by
Parliament for improvements in this branch of mechanics, and also
to the universal approbation and applause of his fellow-citizens."
(2) The Monthly Review or Literary Journal, vol. 58