Longcase astronomical regulator

Ferdinand Berthoud (1727–1807) left his native village of Placemont, near Neuchâtel in the Swiss Jura region, in 1745 and moved to Paris after acquiring his clockmaking skills from an elder brother, Jean-Henri Berthoud (1710–1790).[1] Once in Paris, he encountered the difficulties posed by the restrictions of the guild of clockmakers who excluded anyone not apprenticed to a Parisian master. The guild’s strictures discouraged some excellent clockmakers from opening shops in Paris,[2] but some of the cleverest were able to circumvent the rules by obtaining special dispensation granted by the French king,[3] by joining a category known as ouvriers libres (free workers),[4] or by working in certain places that were exempt from the jurisdiction of the guild (for more information, see entry for 17.19.1600 in this volume). One of these places was a small area on the Left Bank in Paris belonging to the Abbey of Saint- Germain-des-Prés.[5] Whether or not Berthoud worked in this enclosure during 1745–52 is not documented, but historian Jean-Dominique Augarde has suggested that he may have been working for Pierre-Joseph de Rivaz (1711–1772), a fellow Swiss maker of equation clocks and watches at this time.[]6



The situation changed in 1752, however, when Berthoud presented a treatise on the construction of his own equation clock to the Académie Royale des Sciences.[7] Unlike an ordinary clock that records only an arbitrary day of twenty-four hours of equal length (an average based on the length of all solar days in a year), an equation clock registers the time in a solar day (the day that results from one rotation of the earth measured from the sun’s zenith on one day to the its zenith on the next). The period may be more or less than twenty-four hours, depending on the time of year. Solar time is measured by sundials, which were customarily used for setting eighteenth-century clocks. The utility of a clock that could simultaneously measure both twenty-four equal hours and true solar time was highly valued, therefore, if not so easily constructed. Mentioned in the list of “Machines ou inventions” approved by the Académie in 1752,[8] Berthoud’s invention won the support of several influential members, which allowed him a special dispensation to become a master in the Paris guild.[9]



In the following decade Berthoud turned his attention to the construction of marine chronometers. He traveled to London twice during the continuous debates that concerned the award of the prize for a marine chronometer by the British Board of Longitude to John Harrison (1693–1776). While Berthoud apparently never met Harrison, he did see three of Harrison’s chronometers during his first trip in May 1763.[10] Due to an oversight by the Board of Longitude in 1766, Berthoud learned a great deal about Harrison’s last chronometer from Thomas Mudge (1715–1794),[11] the London clockmaker who was a member of the committee convened by the board to judge the practicality of the Harrison chronometer, now commonly known as H.4.[12]



During Berthoud’s second trip to London, in February 1766, the Parisian master clockmaker Pierre Le Roy (1717– 1785), who held a royal appointment and occupied a prestigious, if not commodious, workshop in the Galeries du Louvre, presented a marine chronometer to King Louis XV (1710–1774). In 1769, Le Roy was awarded a double prize for his marine clocks and for describing the best method of determining the time at sea.[13] His rival Berthoud, however, produced two marine chronometers for the French king,[14] and it would be Berthoud, not Le Roy, who in 1770 was appointed clockmaker and mechanician to the king and to the navy.[15] In 1773, Berthoud was further commissioned to produce four marine clocks a year and to supervise all marine clocks made for the French Admiralty. In return, he received a liberal pension for life.[16] Berthoud published plans for a number of his marine timekeepers, including at least one timekeeper that he admitted was influenced by Harrison’s inventions in the Traite des horloges marines (Treatise on Marine Clocks, 1773).[17]



Berthoud’s work on equation clocks is only a little less known than his work on chronometers. In fact, he published a remarkable amount of information about horology between 1753 and 1807, including entries on the equation of time and equation clocks in volume five of the Encyclopedie (1755) by Denis Diderot (1713–1784) and Jean Le Rond d’Alembert (1717–1783). The illustration of the movement of an equation clock shown here, appeared in the second edition of the Essai sur l’horlogerie (Essay on Timekeeping) in 1786 (fig. 48). In the etching, the kidney-shaped element superimposed on the calendar dial of the clock modified the motion of an extra hand (with sunburst), allowing the hand to register true solar time. This system is employed in the Museum’s astronomical regulator with the kidney-shaped piece attached to the back of the calendar dial. In the Museum’s clock, a pin on a springloaded arm that is connected to the calendar and incorporated into the clock rides along the edge of the kidney-shaped piece and regulates the motion of the solar hand.



Whatever Berthoud may or may not have appropriated from Harrison’s chronometers, it is certain that the giant pendulums he employed in longcase astronomical regulators owed a great deal to Harrison and his brother James, whose bimetallic, or gridiron, pendulums were made to prevent the expansion or contraction of the pendulum caused by temperature changes, which influenced the length of the pendulum and the accuracy of its timekeeping. Berthoud’s version of the device did less for temperature compensation than Harrison’s version, as the alternating rods of brass and steel were too thick and mounted too closely together in Berthoud’s pendulums to be wholly effective.



Visually, however, the compensated pendulums were a great success. Berthoud made a series of precision regulators with glass panels in their trunks, which displayed the full length of their pendulums’ ponderous swing. Two of the most elaborate cases for such clocks are in the Frick Collection, New York,[18] and the Château de Versailles, France.[19] These two clocks have sculptural groups atop their hoods that evidently were inspired by a sculptural group by Jean-Baptiste Tuby (1635–1700) of the sun god driving his chariot in the Bassin d'Apollon at Versailles, plaques with scenes of infant personifications of the Four Seasons on their bases, and decorative Neoclassical mounts. A plaque on the Frick Collection’s regulator is signed by the founder Philippe II Caffiéri (1714– 1774) and dated 1767. Another regulator in the series, now in the Wallace Collection, London,[20] like the Metropolitan’s regulator, has a classicizing vase atop its hood, but is more generously supplied with heavy, gilded-bronze mounts. The Frick and Wallace regulators incorporate barometers in gilded-bronze laurel wreaths at the top of the glazed panels on their trunks. The Versailles, Wallace, and Metropolitan cases are made of ebony veneer, whereas the Frick regulator, probably the first in the series, is veneered with tulipwood and kingwood. All four clocks are signed by Balthazar Lieutaud (ca. 1720–1780), a master ebeniste in the Paris guild of cabinetmakers in 1749 who specialized in making clockcases. [21] Probably beginning about 1767, he and Caffiéri created the cases for Berthoud’s regulators, mostly in a severely linear style, but lightened by such departures as the lively crests or the surprising Chinese fret motifs on the base of the Metropolitan’s regulator.



The Museum’s example originally had four hands: one for the hour, two for the minutes, and one for the seconds. The hand for mean time (twenty-four equal hours) is missing; the original gilded-brass hand with the sun image for solar time has been substituted for it. Like the seconds hand, the missing hand would have been made of blued steel.



The white enamel dial registers the hours (I–XII) in black enamel and the minutes (5–60, by fives) with individual lines for each minute along both the inner and the outer circumference of the chapter ring. Applied gold fleurs-de-lis mark each two-and-one-half-minute period. Below the eleven–one o’clock position and above the five–seven o’clock position, the clockmaker’s name, “Ferdinand Berthoud,” appears, and an aperture at the six o’clock position reveals the day of the month. The revolutions of the calendar plate govern the opening and closing of the shutters for winding squares at the four and eight o’clock positions. The dial is protected by a glass lens in a hinged bezel in the form of a snake biting its tail that encircles a beaded border. Vegetal ornament fills the spandrels.



The movement is held in place by two brass arms to which it is secured by means of screws that operate from below the arms. The movement consists of two square plates held apart by five cylindrical pillars. On the right-hand side, it has a weight-driven going train with maintaining power, regulated by a Graham-type dead-beat escapement and the heavy gridiron pendulum that rests on a knife-edge when in service. A screw on the bottom end of the pendulum permits some adjustment to the beat. As the clock has a duration of thirty-four and one half days, it requires a heavy weight with a long fall, the drop lengthened by running its cord over a pulley attached above the back plate. The train drives the epicyclic system for the equation mechanism that is described in principle in Berthoud’s Essai sur l’horlogerie.[22]



The left-hand train of the regulator is the striking train. It is spring driven and strikes both mean-time hours and a single blow at the half hours by means of a hammer and a bell mounted on the back plate. It is governed by a single count wheel mounted on the back plate above the signature of the clockmaker.



The ball finial on top of the vase is probably a replacement. When the clock entered the Museum’s collection, the bottom of the wooden base was found to have been shattered, and it needed replacement. The movement was cleaned and put in running condition. The equation mechanism’s indexing arm was tied off with a wire because if it were put back into service, the clock could be wound only during the few days of the month when the movement of the calendar disk permitted access to the winding squares. As the clock needed a more solid installation than it could be given in the present Jack and Belle Linsky Galleries, it frequently stopped in the course of a month. Therefore, the decision was made not to try to keep it running either with or without engaging its equation mechanism. When properly installed, this regulator, like those mentioned earlier, would have been sufficiently precise to have been usable by astronomers for timing most celestial events.



The earliest record of the regulator appears in the “Art Treasures Exhibition” held in New York in 1955.23 In 1959, it was sold by Thelma Chrysler Foy in New York, and it is described in the sale catalogue as having been owned by Madame Jacques Balsan in New York.[24]



Notes (For key to shortened references see bibliography in Vincent and Leopold, European Clocks and Watches in the Metropolitan Museum of Art. NY: The Metropolitan Museum of Art, 2015)



[1] For details of Berthoud’s apprenticeship and later life, see Cardinal 1984a. A copy of his certificate of apprenticeship appears in Ferdinand Berthoud 1984, p. 303. See also Augarde 1996, pp. 280–82.

[2] Augarde 1996, pp. 15–16.

[3] Ibid., p. 38.

[4] Ibid., p. 14.

[5] Ibid., pp. 40–49, especially p. 46.

[6] Ibid., p. 280. The Swiss-born Henri Enderlin and German-born Michel Stollenwerck, both distinguished clockmakers, were established in the enclosure of Saint-Germain-des-Pres in the 1740s. Ibid., pp. 311, 398.

[7] Established in 1666 by a decree of King Louis XIV for the promotion of French scientific matters.

[8] “Machines ou inventions”1756, p. 147, cited in Cardinal 1984a, pp. 21–22.

[9] See Cardinal 1984a, p. 23, based on a document of the Conseil d’Etat du Roy, Y 9327, in the Archives Nationales, Paris. The document is dated Dec. 31, 1753; see Ferdinand Berthoud 1984, p. 325.

[10] The first three are now in the Royal Observatory in Greenwich, England, inv. nos. ZAA0034, ZAA0035, and ZAA0036. The fourth is in the National Maritime Museum in Greenwich, inv. no. ZAA0037. For more about the four Harrison chronometers, see Gould 1960; see also Betts 1993, pp. 10–16; Randall 1996. For a lively account of the attempts to make a practical marine chronometer, see Sobel and Andrewes 1998.

[11] Randall 1992, p. 21.

[12] For a brief account of what Berthoud adapted from Harrison’sinventions, see Turner 1984a, pp. 154–58; also Sabrier 1984, pp. 165–70. See also note 17 below.

[13] Le Roy 1770. See also Baillie 1978, pp. 280–83.

[14] Cardinal 1984a, p. 31.

[15] Ibid., pp. 32–33; Ferdinand Berthoud 1984, p. 313.

[16] Cardinal 1984a, pp. 36–37. For the quarrel over the priority of the invention, see Cardinal 1996.

[17] See Berthoud’s timekeeper Horloge Marine No. 2 in the Musee National des Techniques, Paris (inv. no. 1387). See Catherine Cardinal and Jean-Claude Sabrier in Ferdinand Berthoud 1984, p. 191, and p. 164, fig. 60.

[18] See Edey 1982, pp. 69–70, 72–75, and cover. See also Heuer and Maurice 1988, pp. 111–13, figs. 200–202.

[19] Inv. no. V 1679VBM 1055. See Calin Demetrescu in Decorative Furnishings 2014, p. 417, no. 171. See also Watson 1960, p. 112, no. 50, and fig. 50; Augarde 1996, pp. 266–67.

[20] Hughes 1994, pp. 57–58.

[21] For more about Berthoud, Lieutaud, and Caffieri’s collaboration, see Jean-Neree Ronfort in Ferdinand Berthoud 1984, pp. 253–54; Ronfort 1984, pp. 113–15. See also Edey 1982, pp. 72–74; William Rieder in Metropolitan Museum of Art 1984, p. 244, no. 150.

[22] Berthoud 1786, vol. 1, pp. 66–72. The horologist Jean-Claude Sabrier has pointed out that Berthoud’s descriptions are so full of detail that his designs can be executed even today by following his instructions. See Sabrier 1984, p. 165.

[23] Art Treasures Exhibition 1955, no. 290.

[24] Parke-Bernet Galleries 1959, p. 186, no. 352, ill. p. 187.