John Arnold (1736 – 11 August 1799) was an English watchmaker and inventor.
Arnold was the first to design a watch that was both practical and accurate, and also brought the term "chronometer" into use in its modern sense, meaning a precision timekeeper. His technical advances enabled the quantity production of marine chronometers for use on board ships from around 1782. The basic design of these has remained with a few modifications unchanged until the late twentieth century. His legacy includes, together with Abraham-Louis Breguet, being one of the inventors of the modern mechanical watch. One of his most important inventions, the overcoil balance spring, is still used in most mechanical wristwatches.
It was from around 1770 that Arnold developed the portable precision timekeeper, almost from the point where John Harrison ended his work in this field. But, compared to Harrison's complicated and expensive watch, Arnold's basic design was simple whilst consistently accurate and mechanically reliable. Importantly, the relatively simple and conventional design of his movement facilitated its production in quantity at a reasonable price whilst also enabling easier maintenance and adjustment.
Three elements were necessary for this achievement: A detached escapement, which gave minimal interference with the vibrating balance and balance spring A balance design that enabled compensation for the effect of temperature on the balance spring A method for adjusting the balance spring, so that the balance oscillates in equal time periods, even through different degrees of balance arc
Early life and work Born 1736, in Bodmin, Arnold was apprenticed to his father, also a clockmaker, in Bodmin in Cornwall. He probably also worked with his uncle, a gunsmith. Around 1755, when he was 19, he left England and worked as a watchmaker in the Hague, Holland, returning to England around 1757.Vaudrey Mercer: John Arnold and Son, pp. 3, 4.
In 1762, whilst at St Albans, Hertfordshire, he encountered William McGuire for whom he repaired a repeating watch. Arnold made a sufficient impression so that McGuire gave him a loan, enabling him to set up in business as a watchmaker at Devereux Court, Strand, London. In 1764, Arnold obtained permission to present to King George III an exceptionally small half quarter repeating watch cylinder escapement watch mounted in a ring. A similar repeating watch by Arnold has survived; it is of interest that the basic movement is Swiss in origin but finished in London. The escapement of this watch was later fitted with one of the first jewelled cylinders made of ruby.
Arnold made another watch for the King around 1768,Now in the Musee International D'Horlogerie at La Chaux-de-Fonds, Switzerland. which was a gold and enamel pair cased watch with a movement that had every refinement, including minute repetition and centre seconds motion. In addition, Arnold fitted bi-metallic temperature compensation, and not only was every pivot hole jewelled but the escapement also had a stone cylinder made of ruby or sapphire. Arnold designated this watch "Number 1", as he did with all watches he made that he regarded as significant, these numbering twenty in all.Report from the Enquiry concerning Mudge's timekeeper by the Select Committee of the House of Commons 1793.
Other early productions by Arnold from 1768 to 1770 display both originality and ingenuity; this includes a centre seconds watch wound up by depressing the pendant once a day. The movement of this watch was also fully jewelled with a temperature compensation device and a ruby stone cylinder escapement.Crott Auctions Mannheim 2008.Patek Phillipe Museum, Geneva
These watches were made as demonstrations of Arnold's talent and, in terms of style and substance, were similar to other "conversation pieces" being made at the same time as those being produced for James Cox and made primarily for export to the East.
Technical challenge Arnold's facility and ingenuity, coupled with his undoubted charm brought him to the attention of the Astronomer Royal Nevil Maskelyne, who at this time was seeking a watchmaker skilled enough to make a copy of John Harrison's successful marine timekeeper. A full and detailed description of this watch was published by the Board of Longitude in 1767, entitled "The Principles of Mr. Harrison's Timekeeper", the intention clearly being for it to act as a blueprint for future quantity production. In fact, it was a highly complex and technically very advanced piece of micro engineering, and capable of being reproduced by less than a handful of watchmakers. However, the challenge was taken up by Larcum Kendall, who spent two years making a near identical copy (now known as K1) that cost £450, a huge sum at the time. Although successful as a precision timekeeper, the Admiralty for obvious reasons wanted a timekeeper on every major ship, and Kendall's was too expensive and took too long to make. Kendall made a simplified version (K2) in 1771, leaving out the complicated remontoir system. But the result was still too costly and, moreover, not as accurate as the original.Rupert T. Gould London 1976 Ed. "The Marine Chronometer" pp. 71–74.
In retrospect therefore, it was a significant occasion when in 1767, Nevil Maskelyne presented John Arnold with a copy of the "Principles of Mr. Harrison's Timekeeper" as soon as it was published, evidently with a view to encourage him to make a precision timekeeper of the same kind. Maskelyne subsequently encouraged Arnold by employing him on several occasions, mostly in connection with watch and clock jewelling. In 1769, Arnold modified Maskelyne's centre seconds watch by John Ellicott, changing the cylinder escapement from steel to one made of sapphire. He lent this watch to the Astronomer William Wales for use in assessing the practicability of Maskelyne's Lunar distance method for finding the ship's longitude during the voyage of the Transit of Venus expedition to the West Indies in 1769. Around this time, Arnold also seems to have started to think about making an accurate timekeeper to find the longitude.
First "Watch Machines" Arnold's approach to precision timekeeping was completely different from that of Harrison, whose technical ethos was rooted in seventeenth- and early eighteenth-century theory and practice. Arnold knew that as the balance and balance spring control the timekeeping in a portable watch. He only needed to find a way of giving the balance a consistent impulse with minimal interference from the wheel work, together with an effective temperature compensation. After making some experimental machines, he produced what could be regarded as a production model to the Board of Longitude in March 1771.
This machine was completely different from Harrison's watch. It was a mahogany box of approximately that housed a movement that, though relatively simple, was close to the same size as Harrison's, with a balance of a similar diameter. The radical difference, however, was a newly designed escapement that featured a horizontally placed pivoted detent that allowed the balance to vibrate freely, except when impulsed by the escape wheel. The spiral balance spring also had a temperature compensation device similar to those in Arnold's watches and based on Harrison's bimetallic strip of brass and steel. Arnold proposed manufacture of these timekeepers at 60 guineas each.Vaudrey Mercer "John Arnold and Son" Pps.24 & 25 Antiquarian Horological Society Publications London 1972.
Three of these timekeepers travelled with the explorers James Cook and Captain Furneaux during their second voyage to the southern Pacific Ocean from 1772 to 1775. Cook also had Kendall's first timekeeper on board as well as one of Arnold's. Whereas Kendall's performed very well and kept excellent time during the voyage, only one of Arnold's was still running on their return to England in 1775. The performance of these clocks was recorded in the logbooks of astronomers William Wales and William Bayly who were assessing their suitability for measuring longitude. Additionally, the log of the HMS Providence (1791) by Captain William Robert Broughton mentions "Arnold's box time-piece keeps so uncertain a rate as to render it useless." Broughton claimed that the time piece gained 0".419 per day on 10 April 1797. Several months later, on 21 October 1797, the time piece had degraded in effectiveness and was losing 9".800 per day.
During this period, Arnold also made at least one precision pocket watch: a miniature version of the larger marine timekeepers.
This surviving watch dates from around 1769–1770 and is signed Arnold No. 1 Invenit et Fecit (Latin for 'invented and made'). The movement, which indicates centre seconds, has a steel balance with a bimetallic temperature compensation strip that acts on the flat balance spring. Though now altered, the original escapement was Arnold's horizontal pivoted detent as fitted to the larger timekeepers, which was, it seems, not entirely successful and needed improvements.
Around 1772, Arnold modified this escapement so that it now was pivoted vertically and acted on by a spring. This was a much more successful arrangement, and it is known that in 1772 at least two pocket timekeepers with this escapement were supplied to Joseph Banks at a cost of £100 (Arnold No.5),Receipt for £100 From John Arnold to Joseph Banks -Banks Papers State Library of New South Wales, Sydney and also Banks' fellow Etonian Captain Constantine John Phipps, 2nd Baron Mulgrave. In a long and detailed article on this matter, published in Australiana November 2014 Vol 36 No. 4, John Hawkins details the association between these two men and the imagined possibility that this instrument is one and the same. The world's first pocket chronometer originally destined for Cook's second voyage, purchased by Banks and lent to Phipps, is known to have been a small centre seconds watch of a similar kind to those made by Ellicott. In 1773, Captain Phipps made a voyage to the North Pole, taking with him not only his Arnold pocket timekeeper and an Arnold box timekeeper in gimbals, but also Kendall's "K2" timekeeper. From Phipps's account, it appears that the pocket watch performed very well indeed and was a convenient instrument for ascertaining the longitude.Constantine John Phipps "A voyage towards the North Pole" London 1774.
It seems likely that before 1775, Arnold's earliest pocket chronometers, such as those supplied to Phipps and Banks, were plain watches with centre seconds motion, largely resembling Maskelyne's cylinder watch by Ellicott. Certainly, those few surviving examples are of this caliper such as No. 3.British Museum Cat. No.4
By 1772, Arnold had finalized the design of his pocket timekeepers and started series production with a standardized movement caliper, this being around 50 mm in diameter, larger than a conventional watch of the period, and showing seconds with a pivoted detent escapement and spiral compensation curb. However, the latter appears to have proved ineffective, which seems to have substantially slowed the rate of production.
Even though he produced a number of pocket timekeepers, from around 1772–1778, Arnold was still experimenting with different types of compensation balance and methods of balance spring adjustment. The most difficult problem to surmount was the problem of making an effective and continuously adjustable temperature compensation device. For technical reasons, the temperature compensation for the balance spring had to somehow be incorporated into the balance itself and not act on the balance spring directly as had been done previously by Arnold and others.
First patent