Ferdinand Berthoud, born in 1727 at Plancemont, near Couvet, in the principality of Neuchatel, now in Switzerland, and died in 1807 at Groslay, in France, became a master watchmaker in Paris and ranked among Europe's leading specialists in marine chronometers. After the successful trials of his marine clocks nos. 6 and 8 in 1768 by Fleurieu and Pingre aboard the corvette L'Isis, during a return voyage from Rochefort to Saint-Domingue, he was appointed Horologist-Mechanic to the King and the Navy. His instruments were carried on several major French expeditions, including those of Kerguelen, La Perouse and d'Entrecasteaux.
Ferdinand Berthoud's writings also formed part of the scientific culture within which the expedition operated. His Traite des horloges marines and Traite des montres a longitudes set out the principles and methods of constructing marine timekeepers, while his Histoire de la mesure du temps par les horloges, published in 1802, offered a broader reflection on the history of time measurement through horological mechanics.
His nephew Louis Berthoud continued and developed this legacy. Trained from 1769 in Ferdinand's Paris workshop, he in turn became one of the principal French makers of marine chronometers. The Baudin expedition received four Louis Berthoud marine timekeepers, numbered 27, 31, 35 and 38. Nos. 31 and 38 were carried aboard Le Geographe, while the other two were placed on board the Naturaliste.
To take the example of Cape Berthoud, in order to calculate its longitude Boullanger had to compare the time indicated by timekeeper no. 38, which preserved the time of a Paris meridian, Greenwich not yet having become the universal reference meridian, with the local time at the ship's position, determined from the position of the Sun or the stars. The difference between Paris time and local time was then converted into degrees, at the rate of fifteen degrees of longitude for each hour. The running of the instrument also had to be regularly checked and corrected, since humidity and changes in temperature could affect the mechanism and alter its rate.
The name Cape Berthoud thus recalls the essential role played by timekeeping instruments in the hydrographic survey of the coasts, while Berthoud Island extends, within the group of the Institut Islands, the tribute paid to a line of horologists whose work was closely linked to advances in scientific navigation. Today, three of the marine timekeepers made by Louis Berthoud are known to survive: no. 31 in the Musee national de la Marine in Paris, no. 38 in a private collection, and no. 35 in the Silentworld collection.