FERDINAND BERTHOUD | Description of a pocket watch by Jean Martin.

Ferdinand Berthoud Astronomical Chronometer N° 3, Paris, 1806 - by Jean Martin

An article by Anne Walter, Heritage Manager, and Vincent Lapaire, Project Manager.

Discover an exclusive detail of the future FERDINAND BERTHOUD timepiece, and the Astronomical Chronometer N° 3, Paris 1806, by Jean Martin (one of Ferdinand Berthoud's students).

FERDINAND BERTHOUD, new watch, caliber
Partial view of the dial for the new FERDINAND BERTHOUD watch currently under development
Silver astronomical chronometer N° 3, FERDINAND BERTHOUD
Astronomical chronometer N° 3, FERDINAND BERTHOUD, made by Jean Martin, Paris, 1806 - L.U.CEUM collection

A Parisian workshop on the Ile de la Cité

Ferdinand Berthoud did not devote his life exclusively to research and experimental projects relating to the production of Marine Clocks.

He graduated as a Master watchmaker on December 4th 1753 at the age of 26. Two months later, on February 7th 1754, Ferdinand Berthoud set up shop as a watch and clock maker at 36, Rue de Harlay, passage Saint Barthelemy, in Paris. This was a prestigious address, located between the Quai de l’Horloge and the Quai des Orfèvres, on the Ile de la Cité, in the current 1st arrondissement (borough). The Cité has been home to a number of famous watchmakers, such as Pierre Le Roy (1717-1785), Abraham-Louis Breguet (1747-1823) and later, Jean-Antoine Lépine (1720-1814).

In his workshop, Ferdinand Berthoud provided top-quality production aimed at the general public as well as scientists of his time. In order to do this, he surrounded himself with qualified workers and apprentices that he undertook to train.

The most famous of his apprentices was his nephew Pierre-Louis (known as Louis) Berthoud (1754-1813), who Ferdinand summoned from Couvet (Switzerland) to Paris in 1769, and who supported him effectively in the manufacture and maintenance of Marine Clocks made for the French and Spanish Navies. Louis Berthoud subsequently took over Ferdinand’s workshop in 1784. His work was so important that we will devote a special section to him.

Jean Martin, a student of Ferdinand Berthoud

One of Ferdinand Berthoud’s favourite students, Jean Martin, to whom he pays tribute in Supplément au Traité des Montres à Longitudes (Supplement to the Treatise on Longitude Watches), published in Paris in 1807, was born in his house, at Groslay, Île-de-France, in 1773.

At the age of 13, after having worked for a while in the workshop of the Master, who recognised his “skill and intelligence”, he was sent by Berthoud to one of his disciples, Jacques-Vincent Martin, who had established himself in Brest as a Naval watchmaker since 1785. His job involved “not simply cleaning large weight driven clocks, restoring them to seaworthy working order and taking charge of them when they returned from voyages, but also making new Longitude Watches for naval use” (as stated in a letter from Ferdinand Berthoud, Paris, National Archives, Marine G 97, f. 94).

Jean Martin remained in Brest for five and a half years and returned to Groslay in 1793. Under Ferdinand Berthoud, and over a ten-year period, he produced several longitude clocks and watches as well as the one-year Astronomical Clock. Berthoud then suggested that he move to Paris and entrusted the creation of several watches to him, notably for Louis Monge (1748-1827), a French mathematician, and for Baron Louis-Bernard Guyton-Morveau (1737-1816), a chemist and French politician.

A Ferdinand Berthoud watch made by Jean Martin

Part of the special collection of the L.U.CEUM, in Fleurier (Switzerland) the N° 3 Astronomical Pocket Watch made by Ferdinand Berthoud in Paris in 1806 was in fact crafted by Jean Martin.

This exceptional piece is described in detail in the Supplément au Traité des Montres à Longitudes (Supplement to the Treatise on Longitude Watches), in chapter IV, article XX, points N° 111 to 116.

The dial of the watch bears the inscription “Montre Astronomique N° 3 Ferdinand Berthoud, Inv. 1775, Réduite et Exécutée par Jean Martin, An 1806” (Ferdinand Berthoud Astronomical Watch N° 3, Inv. 1775, Reduced and Executed by Jean Martin, Year 1806). At the time, the watchmaker who had made the watch traditionally placed his signature on the dial in this way.

Dial detail, FERDINAND BERTHOUD astronomical chronometer N° 3.
Dial detail of the FERDINAND BERTHOUD astronomical chronometer N° 3

The Count of Chanteloup, an eminent owner

The N° 3 Astronomical Pocket Watch bears the coat of arms of Jean Chaptal, the count of Chanteloup, a scientist and politician. Born in 1756, Jean Chaptal was a chemist well-known for the chemistry applications that he introduced to industry, notably in the realm of textile manufacturing. He created a factory for chemical products which became known all over Europe and received several titles from Louis XVI.

Chaptal also gave his name to chaptalisation, a process that makes it possible to increase the alcohol content in wine with sugar. This discovery revolutionised the art of winemaking.

Parallel to his activities as a scientist, a chemist and an industrialist, he was also Minister of the Department of the Interior under Napoleon Bonaparte. Initially a Senator and then pair de France (French peer) during the Hundred Days and under the Restoration, he died in 1832.

Astronomical chronometer N° 3, FERDINAND BERTHOUD, Jean Martin, L.U.CEUM collection
Astronomical chronometer N° 3, FERDINAND BERTHOUD (made by Jean Martin), Paris, 1806 - L.U.CEUM collection

A pocket chronometer inspired by a longitude watch

In order to create the N° 3 Astronomical Watch, Ferdinand Berthoud initially intended to re-use a modified plan of the Third Astronomical Watch, which dated from 1775, and then that of his N° 72 vertical and portable longitude watch, made in 1803.

Finally, he used the geartrain plan from the N° 73 Clock, which can be seen in fig. 6 of the Supplément au Traité des Montres à Longitudes (Supplement to the Treatise on Longitude Watches).

He explains that the seconds are positioned in the centre, while the minutes and hours are presented on an off-centre dial.

The wheels of the N° 3 Astronomical Pocket Watch are similar to those in the N° 73 Clock. They have the same diameter and same number of teeth.

However, the watch is smaller due to the removal of the rollers, the compensation mechanism and the balance-wheel warning levers. As a result, the mainplate on the dial side is also smaller in diameter.

The reduction of the going train is the work of Jean Martin. Nevertheless, in the smaller dimensions of the N° 3 Astronomical Pocket Watch, it maintains the same driving force as in the N° 72 Longitude watch, due to a powerful barrel-spring and by using the entire height of the case.

The balance-wheel, which describes 260-degree arcs, oscillates a rate of four vibrations per second. As described by Berthoud, its pivots turn in “cap jewels” (endstones or cap stones).

Temperature variations were entirely compensated for by a balance-spring fitted four small composite weights. Its blades were arranged in a circular or radial outline. All the pivots in the gear train were also inserted into the “cap jewels”.

Chronomètre astronomique n°3, escape wheel, Ferdinand Berthoud
Detail of the FERDINAND BERTHOUD astronomical chronometer no. 3 escape-wheel

Greater precision thanks to the diamond

In the Supplément au Traité des Montres à Longitudes (Supplement to the Treatise on Longitude Watches) Berthoud asserts the perfect execution of the N° 3 Astronomical Pocket Watch, and considers it to possess the ideal qualities and conditions to meet the requirements of devotees of perfection while enabling astronomic observation. In the event of use to determine longitudes at sea or on land, he adds that it would be preferable to always use the watch in a horizontal position, like the small N° 73 Clock.

With this aim, he had the watch modified and replaced the ruby of the cap jewel with a diamond, which is harder and a better guarantee of increased precision. He also created a suspension so that the watch could be perfectly used horizontally. Later, he indicated that he was perfectly satisfied by the result and that these modifications were beneficial. Indeed, the watch demonstrated great accuracy when in a horizontal position.

Consequently, Ferdinand Berthoud’s little masterpiece can be used as a watch that may be worn either verticals, or horizontally like a small longitude clock.

astronomical chronometer N°3, diamond cap jewel, Ferdinand Berthoud
Focus on the diamond cap jewel on FERDINAND BERTHOUD astronomical chronometer N° 3


Berthoud, Ferdinand, Supplément au Traité des Montres à Longitudes, suivi de la Notice des Recherches de L’Auteur, depuis 1752 jusques en 1807, Paris : Imprimerie J.- M. Eberhard, 1807. (Supplement to the Treatise on Longitude Watches, followed by the Notice of the Author’s Research from 1752 to 1807)

Collective work (Catherine Cardinal et al.), Ferdinand Berthoud 1727-1807, Horloger Mécanicien du Roi et de la Marine, La Chaux-de-Fonds : Musée International de l’Horlogerie, L’Homme et le Temps, 1984.

Collective, The Sandberg Watch Collection, Geneva: Antiquorum Auctioneers, 2001, pp. 184-185.

Friess, Peter, L.U.CEUM Traces of Time: The Chopard Manufacture Collection, Munich: Callwey, 2006.

Discover our other newsletters:
- Ferdinand Berthoud, a watchmaking genius in the service of mariners ; an article by Michel Jeannot
- Ferdinand Berthoud, his contribution to horology ; an article by Catherine Cardinal

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