His initial successes as a researcher and the awarding of the title of master by order of the King
Obliged to work as a watchmaker’s companion for the masters of the Parisian guild, due to not having served his apprenticeship with one of them, the young Berthoud managed to overcome this hurdle by drawing attention to “his considerable application in perfecting the art of watchmaking”. He seized the opportunity of publishing his research at the French Royal Academy of Science by submitting the description of a new construction in a sealed envelope.
The academics’ approval on April 26th 1752 of a longcase equation clock, considered highly ingenious, marked the beginning of his career as a researcher and at the same time, enabled him to stake his claim of official integration within the watchmaker community. On December 4th 1753, the King ordered that he be named a maître (master), a title that allowed him to open a workshop in the Rue de Harlay, near Place Dauphine.1
In 1754, the master once again submitted his inventions to the Academy. One was his first marine clock project2. The others, examined and approved by the academics, were also equation systems: “a longcase equation clock with concentric seconds marking the months and days of the month, leap years, and which runs for 13 months without being wound”; as well as a watch with seconds and equation, marking the months and days.
Even prior to being named a master, Ferdinand Berthoud indicated the direction he wanted his career to take – namely to devote himself to research and transmit his know-how through publications and teaching3. This double vocation enabled him to rapidly make a name for himself in the scientific world of his time.
Several articles in the Encyclopaedia published by Diderot were entrusted to him, and most particularly the article entitled “Equation”. In 1759, he published a successful treatise on popularization entitled, L’Art de conduire et de régler les pendules et les montres. A l’usage de ceux qui n’ont aucune connaissance d’horlogerie (The art of operating and adjusting clocks and watches. To be used by those with no knowledge of watchmaking). In 1763, his extensive treatise - L’Essai sur l’horlogerie ; dans lequel on traite de cet Art relativement à l’usage civil, à l’Astronomie et à la Navigation (An Essay on Horology; in which we deal with this Art in relation to its civil application, to Astronomy and to Navigation) was also well received.
- 1. See Ferdinand Berthoud (1727-1807), directed by Catherine Cardinal, Musée international d’horlogerie (International Watchmaking Museum), La Chaux-de-Fonds, 1984, p 21-22 and p 304 (Decree by the King).
- 2. Berthoud traces his origins in marine watchmaking to this machine which remained mysterious until the opening of the letter in 1976. Op.cit., p 305-308.
- 3. “Letter on Horology”, published in May 1753 in the Journal helvétique.
Affirmation of his vocation and official recognition of his work
1763 marked a turning point in Berthoud’s career, which was now bound up with the development of maritime navigation. The Academy of Science once again both witnessed and supported the horologist’s request for the opening of two reports, respectively deposited in 1760 and 1761. These described the N°1 maritime clock.
Convinced by his skill, the academics obtained permission from the Minister of the Navy to send him to London to examine the Harrison marine clock. This opportunity demonstrated his worth and resulted in his nomination as a foreign member of the Royal Society on February 16th 1764. On August 29th of that year, Ferdinand Berthoud once again made a submission concerning the “construction of a marine watch…” This was the last time, as Berthoud was now sure of where he was going with his research and of having the option of seeking official support.
His projects were the subject of detailed requests punctuating his activities and in this context, he suggested the construction of two marine watches on May 7th 1766.
After successful experimentation with the N° 6 and 8 which are housed at the Musée des arts et métiers (Museum of Arts and Crafts), Ferdinand Berthoud was awarded a certificate entitled Brevet d’horloger Méchanicien du Roi et de la Marine ayant l’inspection de la construction des Horloges marines (Watchmaker and Mechanic to the King and Navy with construction inspection of marine clocks) created especially for him on April 1st 1770.
From this time onwards, he abandoned the management of his workshop-boutique in favour of his research. He confirmed in 1792 that: “It is mainly since 1770 that I have been completely focused on this and I have in a way left the field of public work”.
- 4. Regarding this clock (Musée des arts et métiers,(Museum of Arts and Crafts) Paris, inv. 1386), op.cit. p 191-193 et p 25-26.
- 5. The Watchmaker Mechanic to the King and Navy certificate is reproduced on p 313 of the same work.
Precision clocks and watches for the public
The Tablettes royales de renommée (the renowned royal tablets) highlighted the fame of the watchmaker “Berthoud (Ferdinand) on Rue du Harlay as one of the most famous for the most precious and complicated longcase, as well as marine, astronomical and equation clocks, etc.” (1772).
His work was indeed not confined to the production of marine clocks. His designs supplemented with descriptions, his inventions registered at the Academy, his works that have been preserved, the journal he wrote from 1760 onwards – 23 volumes kept at the Bibliothèque du Conservatoire des arts et métiers (Library of the Conservatory of Arts and Crafts) - all provide a glimpse of his role in the development of civil watchmaking. Precision regulators; longcase equation clocks; watches, often with seconds and repeaters, sometimes with an equation or a calendar; as well as astronomical chronometers all demonstrate Ferdinand Berthoud’s inventiveness and the quality of the works created in his Parisian workshop, and particularly when he was still directing it6.
All the questions in current research regarding watchmaking precision were studied by Berthoud: escapements, whether of the cylinder, detent or lever type; the problem of friction; the isochronism of the sprung balance; thermal compensation; the indication of true and mean time. His research was often conducted for the benefit of both marine clocks and their civil counterparts. Let us look for example at the dissertation on the subject of a self-winding marine watch with a double balance-spring, submitted to the Academy of Science in 1764. The watchmaker noted in conclusion: “I am also going to work on a pocket watch which will be made according to these principles. I have even done the plan.”
- 6The exhibition held in 1984-1985 at the Musée international d’horlogerie (International Watchmaking Museum, at the Musée de la Marine (Maritime Museum) in Paris, and at the Musée d’histoire (History Museum) in Besançon display a collection of a number of important works by Ferdinand Berthoud described in the catalogue. A number of others which are kept in public and private collections must be added to this.
A construction epitomising the era: equation clocks and watches
Equation clocks and watches, which make it possible to follow the difference between real (sun) time and average time on the dial, attracted Berthoud’s attention very early on. In 1752 and 1754, academics admired his simplified construction, characterised by a mobile dial with real time minutes and by a minutes hand, fundamentally equipped with an openwork index in the shape of a sun, thus allowing both times to be read simultaneously. Proud of his system, in 1754 the watchmaker presented an equation watch with concentric seconds noting the months and their days. This watch – signed and dated “Ferdinand Berthoud N° 144, Invenit et Fecit 1753” – appeared on the market, evidence of the virtuosity of the young horologist who drew his innovative inspiration from earlier models7. Amongst his remarkable equation and calendar clocks, equipped amongst other things with a barometer, and luxurious with their bronze decorated cabinets, one may recall the Frick Collection regulator, dated 1767, and the similar example from the Wallace Collection8.
- 7. Auction at Antiquorum, Geneva, November 14th 1993, N° 83, p 134-135..
- 8French Clocks (Winthrop Edey), The Frick Collection, New-York, 1982, p 69-75 ; Clocks and Barometers in the Wallace Collection (Peter Hughes), 1994, p 56-57.
A key issue in research: temperature compensation
The influence of changes in temperature on clock mechanisms was a fundamental problem that Ferdinand Berthoud focused on resolving both for his clocks and for his astronomical watches.
In 1763, he published his research on “the most perfect astronomical clock possible” which he equipped with a compensating pendulum with three rods, two made of steel and one brass. A regulator of this type, with equation and calendar, belongs to the Musée des arts et métiers (Museum of Arts and Crafts - inv. N° 22591). He mostly chose gridiron pendulums with nine rods, like the astronomical clock which belonged to the Count of Cassini, director of the Observatory, the delivery of which was certified by a receipt signed by the watchmaker: “in payment of an astronomical clock made by me… which will run for a month without being rewound, with the pendulum composed in a chassis to compensate the effects of hot and cold …”
Ferdinand Berthoud introduced a “chassis” in a first version of the astronomical watch dated 1764. A second version of the astronomical watch was improved in 1775. Subsequently, inspired by plans for the N°73 longitudinal clock, a variation was made by his student Jean Martin in 1806 and this chronometer delivered to Chaptal is part of the L.U.CEUM collections. Compensation is ensured by the bimetallic balance-wheel with four radial arms, carrying four weights with gold adjusting screws. One may compare this model with the chronometer dated 1796, which was also made by Martin (Louvre Museum, OA 8530) and the one used by the member of the French Academy, Laplace (Paris Observatory, N° 38129). Berthoud was convinced of the advantages of compensation via a bimetallic balance-wheel but, prior to this, he had often adjusted the length of the balance-spring to compensate for temperature variations through the use of a bimetallic blade equipped with a “balance-spring clamp”. In the context of this research, he undoubtedly detected from the 1770s onwards certain compensation irregularities at intermediate temperatures, to which the term ‘secondary error’ was later applied. His countryman, Charles-Edouard Guillaume, who corrected this defect in 1899 by means of his integral balance, provided him with the first opportunity to observe this invention9.
A tenacious investigator, a skilled and daring builder, and an inventor anxious to share his knowledge, Ferdinand Berthoud not only took part in improving horology; he also fostered the use of precision clocks in the sciences of his time, thus contributing to their progress. The title, privileges, and forms of recognition which punctuated his career, between the reign of Louis XV and the First Empire, as well as the tributes and studies which marked his critical fortune until the present day, reflect the importance of his position in the long quest for precision, from Huyghens’ discoveries right up to Guillaume.
- 9Ch.-Ed. Guillaume, L’invar et l’élinvar, Nobel Prize for Physics presentation in 1920, Swiss Chronometry Society, 1974, p 31.
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- Ferdinand Berthoud, a watchmaking genius in the service of mariners ; an article by Michel Jeannot