John Arnold

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John Arnold : biography

1736 – 11 August 1799

Two other makers also made precision watches with the detached escapement, Josiah Emery and John Brockbank. Both were friends of Arnold, and both employed the highly skilled workman and escapement maker Thomas Earnshaw. Josiah Emery used with Arnold’s permission, an earlier form of his compensation balance and helical balance spring, in conjunction with the detached lever escapement of Thomas Mudge,Plate 178 P.290 The English Watch Camerer Cuss. Antique Collectors Club publication 2009 ISBN 978-1-85149-588-7. and John Brockbank employed Earnshaw to make his pattern of chronometer but with Brockbank’s design of compensation balance.Pages 3-15 "An Appeal to the public" Thomas Earnshaw British Horological Institute reprint 1986. ISBN 0-9509621-2-0.

In 1780, while making these chronometers for Brockbank, Earnshaw modified the pivoted detent by mounting the locking piece on a spring thus dispensing with the pivots. Arnold managed to see this new idea and promptly took out the 1782 patent for his own design of spring detent, but it is not known whether this preceded Earnshaw’s own idea.Page 3 – "An Appeal to the public" Thomas Earnshaw British Horological Institute reprint 1986. ISBN 0-9509621-2-0.

Therefore, there has been a great deal of debate over who invented the spring detent escapement, Arnold or Earnshaw. This argument, first initiated by Earnshaw has been continued by horological historians such as Rupert Gould to the present. However the argument is irrelevant. In recent years, research has established that Arnold’s success was not due to the form of detent escapement, but to his original methods of adjusting the balance spring for positional errors by manipulating the overcoil terminal curve. For obvious reasons Arnold tried to keep these methods secret, certainly it is recorded that he clearly expressed his concerns about possible plagiarism to Earnshaw, warning him in no uncertain terms not to use his Helical balance spring.Page 15 "An Appeal to the public" Thomas Earnshaw British Horological Institute reprint 1986. ISBN 0-9509621-2-0.

Nevertheless, a year later, in 1783, Earnshaw—through another watchmaker, Thomas Wright—took out a patent that included Earnshaw’s pattern of integral compensation balance and spring detent escapement in the multiple specification. However both of these were undeveloped and compared to Arnold’s were of little use, the balance especially having to be redesigned.Thomas Wright "Watch or Timekeeper" G.B. Patent No.2489 25/4/1783.Pages 13 – 14 "An Appeal to the public" Thomas Earnshaw British Horological Institute reprint 1986. ISBN 0-9509621-2-0.

Eventually, after much argument, the Board of Longitude granted Earnshaw and Arnold awards for their improvements to chronometers. Earnshaw received £2500 and John Arnold’s son, John Roger Arnold, received £1672. The bimetallic compensation balance and the spring detent escapement in the forms designed by Earnshaw have been used essentially universally in marine chronometers since then, and for this reason Earnshaw is also generally regarded as one of the pioneers of chronometer development.

However, because Arnold’s balance spring patents were in force (each for 14 years) Earnshaw could not use the helical balance spring until the 1775 patent lapsed in 1789, and in the case of the 1782 patent, 1796. Until around 1796, Earnshaw made watches with flat balance springs only,Catalogue of precision watches in the British Museum. 1990 ISBN 0-7141-0551-1 Cat. No. 58 P.80. This chronometer by Earnshaw also originally had a flat spring, later converted to helical.Clutton & Daniels – Catalogue of clocks and watches in the Collection of the Worshipful Company of Clockmakers Sothebys publication 1975 ISBN 0-85667-019-7 Page 58 Catalogue No. 427. but post 1800 practically every marine chronometer including those by Earnshaw had a helical spring with terminal overcoils.

Arnold was the first to produce marine and pocket chronometers in significant quantities at his factory at Well Hall Eltham from around 1783, during the next 14 or 15 years he produced hundreds before he had any kind of commercial competition.Hans Staeger 1997 – 100 years of Precision Timekeepers from John Arnold to Arnold & Frodsham 1763-1862. Private Publication. See pages 161-182. The facts prove that authors such as Gould and Sobel are incorrect in their assertion that there was commercial rivalry between Arnold Sr. and Earnshaw.Antiquarian Horology Volume 17 No.4 Pages 368 – 371 This shows that between 1783 and 1796, even excluding marine chronometers, Arnold produced at least 500 pocket chronometers. In comparison, Earnshaw made only a few chronometers, perhaps fewer than fifty, during this period. Only a handful survive that date from before 1796 and, significantly, all have (or originally had) flat springs.