A very rare and important Second Empire astronomical gilt bronze wall regulator by Louis-Constantin Detouche and probably Jacques-Francois Houdin, signed on a cartouche within the dial C Detouche Paris and numbered 9730, with mean time and the following five following horological complications: power reserve, date of the month, day of the week, month of the year and 'sectorielle' equation of time showing the true time.

The main gilt brass dial enclosed by a palmetted bezel, the chapter ring with twelve large circular white enamel cartouches with black Roman numerals for the hours, an outer white enamel minute ring to include twelve smaller circular cartouches with black Arabic numerals and an inner seconds ring (later period, probably in bakelite), showing at six o'clock a graduated sectorial dial for the power reserve inscribed HAUT/BAS, with winding hole at centre, with blued steel Breguet hands for the hours and minutes and blued steel pointers for the seconds and power reserve. Below the main dial a secondary dial with palmetted bezel with outer white enamel calendar ring showing the date of the month, the day of the week, and the month of the year with its duration (28, 30 or 31 days), centred by an annual rotating marker for the date on which is the mechanism for the equation of time, given on a white enamel sectorial dial with indications painted in black graduated from +15mn to -15mn and AVANCE/RETARD, with annual calendar and the equation kidney visible through the centre, all against a gold star-studded blue enamel ground, with Breguet hands and a blued steel counter balanced hand for the mean time and gilt brass solar hand for the real time.

The 15 day going steel and brass weight driven movement with recoil anchor escapement with micrometric regulator and remontoir d'égalité and a steel and gridiron compensating pendulum placed before an engraved false plate to protect it from interferences from the descent of the weight, the massive bob centred by a thermometer with a white enamel sectorial dial, graduated from -10⁰ to 30⁰ Celsius with a blued steel balanced needle, the movement on a gilt brass bracket secured by polished steel screws, the pendulum suspended from the top of the case by a steel cable. The rectangular glazed gilt bronze case with stepped cornice and a pierced scrolled terminal

Paris, date circa 1855-60

Height 185 cm, width 47 cm, depth 29.5 cm.

This rare and important astronomic wall regulator can be considered as one of the most beautiful ever seen. Made in the mid nineteenth century it is a masterpiece made by Louis-Constantin Detouche (1810-1889) and probably Jacques-François Houdin (1783-1860), his foreman or chef d'atelier from 1845-59. Restrained in style, it demonstrates many noteworthy characteristics of execution and an exceptional mechanical design that are typical of other masterpieces shown by this prestigious company at the various industrial and universal exhibitions where it won numerous gold and other medals. In addition to being bestowed the French Légion d'Honneur (1853), and the Danish Croix de l'ordre du Dannebrog, Detouche was an official clockmaker to the city of Paris and the Emperor Napoleon III. His company, which was probably the most important French horological firm of its day, was constantly developing and its success brought both critical and financial rewards. In a review of the Nimes exhibition of 1862, the House of Detouche was singled out by one critic, whose words give an insight into this exceptionally gifted business. The critic noted "Horology was represented with dignity at the Nîmes exhibition. Above all, we shall cite the House of Detouche de Paris, founded in 1803; its business has increased annually and now retails in France and abroad more than 3 million francs worth of goods. In this figure, horology, from precision items to those for domestic use represent more than 1,200,000 francs.

M. Detouche has already received the most prestigious awards; I will just mention: the gold medal at the Exposition Universelle d'Horlogerie at Besançon in 1860, and the gold medal in London in 1862. He was awarded La Croix de la Légion d'Honneur for his contribution toward the progress in horology that resulted from his work, the Croix de Dannebrog was awarded to him by the King of Denmark for his electric clock. Such items deserve to be described in a few details. They present improvements worthy to be known and appreciated by every clockmaker who has benefited from M. Detouche's work and true service… The jury noted secondly a rocaille style regulator in gilt bronze of a remarkable taste, measuring 1m, 90;…The turnstiles placed at the exhibition and considered indispensable in France and abroad are also the invention of M. Detouche. All of the items shown by this company are to be noted for their modest prices, their elegance, their rich ornamentation and precision, and their skilled workmanship. The jury awards to M. Detouche a diplôme d'honneur." ("Revue Chronométrique, 8th year, vol. IV, June 1862 - June 1863, "Exposition de Nîmes", Paris, 1862, pp. 605-609).

Constantin-Louis Detouche (also known as Détouche) was born in Paris on 10th October 1810. An ingenious mechanic and creative inventor, throughout his life Detouche took out many patents or brevets for his numerous inventions. On 30th December 1844 he took out one for his invention of an alarm clock with mobile keys. The following year, 1845 up until 1859 Detouche hired Jacques-François Houdin (1783-1860) as his foreman. The latter, who was a member of several scientific associations and father-in-law to the ingenious inventor, magician-extraordinaire and horological genius Jean-Eugène Robert-Houdin (1805-71), came from Blois but decided to move to Paris at Abraham-Louis Breguet's request. Like Detouche, Jacques-François Houdin's work was remarkable for its quality, exceptional finish and technical complexity and thus helped establish the outstanding reputation of the Detouche Company. Houdin's legacy also included the creation and improvement of special escapements and compensating pendulums for regulators and astronomical clocks along with certain improvements in the design of machinery used in the making of wheels and pinions.

Within six years of Houdin joining the firm, Detouche showed its work at the Great Exhibition of London, 1851 (the very first universal exhibition). On 26th February of the following year Detouche took out a patent with F. Brisbard-Gobert for an electro-magnetic clock. Yet another of his inventions was patented on 8th May 1852, this time for a pendulum suspension system. Then on 22nd July 1852, he gained a patent with Jacques-François Houdin for a new sonnerie mechanism for clocks. In 1855 Detouche showed his works at the Paris Exposition Universelle, where he received a gold medal. The same year he donated two clocks to the Conservatoire Impérial des Arts et Métiers de Paris, namely: a master clock with electro-mechanical escapement, Robert-Houdin's system, Inv. 6 356 and a receiver clock (shown at the Exposition Universelle, Paris in 1855), Inv. 6 357. Detouche also gave the Conservatoire Imperial des Arts et Métiers a collection of six demonstration escapements made by Jacques-François Houdin (shown at the Exposition Universelle, Paris in 1855); a Ferdinand Berthoud anchor escapement for clocks, Inv. 6 602; a crank lever escapement from Deshays, 1854, Inv. 6 603; a coup perdu escapement from Jacques-François Houdin, 1854, Inv. 6 606; an escapement from R. Robert, 1854, Inv. 6 607; a constant force escapement from Houdin, Inv. 6 605 and lastly a two sphere constant force escapement from Auguste Verité, Inv. 6 604.

May 24th 1856 saw him taking out a patent with Jean-Eugène Robert-Houdin for an electrical dial that could be used on the city's gas lanterns. Then in 1860, Detouche showcased his products at the Exposition de Besançon, where he obtained no less than a gold medal. This success was followed in similar fashion when in 1862, Detouche showed at the Universal Exhibition, London where he once more received a gold medal. The following year, Detouche gained yet another gold medal when he exhibited at the Exposition de Nîmes, 1863. That same year he donated a monumental clock, made at the end of the 1850's as a special order for the Conservatoire Imperial des Arts et Métiers, Paris, which was placed in the museum lobby and operated the façade dial and bell; that clock, presented in 1860 to the Société des Encouragements des Arts de Paris, gained Houdin and Detouche a silver medal. Detouche then took out a patent with Chéradame, 13th April 1864 for improving the illumination of clock dials for night viewing. This was followed on 7th February 1866 by him taking out a patent for a system for the transmission of movement without the use of angle wheels for use in so-called mystery clocks. He then took out a patent for another invention of an alarm clock with a spherical case, on 17th February 1866.

Toward the end his life, in 1887, Detouche provided the funds for the publication of the third edition of the "Traité d'Horlogerie Modern Théorique et Pratique" by Claude Saunier (1816-1896), also known as the C. Detouche edition (published Paris, containing 944 pages) and the addendum (also published Paris containing 112 pages).

Among other of Detouche and Houdin's most prestigious creations one should note two large astronomical regulators of differing designs, bearing numerous indications such as hours, minutes, seconds, days, months and their dates, sunrise and sunset time, the equation of time, moonrise and moonset, its phases along with its age, as well as the barometric and thermometric variations. On them the main dial is surrounded with fourteen subsidiary dials showing the time in fourteen cities across different latitudes. Those two pieces were adjusted with a compensating pendulum, which was technically innovative for its day. One of the two remained for a long time at the corner of rue Saint-Martin and rue de Rivoli and is now housed in the exhibition room of the watch manufacture, François-Paul Journe SA, Geneva. Other works of distinction include a regulator known as Ephéméridal, which at midnight shows the daily position of the planets during the day, as well as an astronomical clock of 1851 that indicates the mean time, the date, the day, the month of the year, the equation of time and the time of sunset and sunrise (private collection, Milan). This piece was shown at the centennial retrospective exhibition of horology during the Exposition Universelle de Paris in 1900; it was then owned by the Parisian Jules-Rene Olivier (1855-1933), whose sister Marie-Julie gave part of his collection to the Musée du Louvre in 1935.

The present regulator includes many specialized mechanisms that should be mentioned including a remontoir d'égalité; this clever mechanism was used to apply a controlled force to impulse the pendulum or balance in order to overcome variations in timekeeping caused particularly by variations in the driving motor; at regular intervals the remontoire winds up a secondary spring or small weight, which in turns transmits a force as consistent as possible to the escapement wheel. In the constant force escapement, this auxiliary spring is triggered by the movement of the pendulum; hence the strength produced is, in theory, always the same. Detouche's regulator also shows equation of time, which in effect is the difference between apparent solar time (the time shown at any place on a sundial) and mean time (the time shown by a clock running uniformly throughout the year). The difference arises from two factors, firstly the earth's orbit around the sun and secondly its rotation about its own axis. Because the earth's orbit around the sun is elliptical rather that circular the sun's apparent motion is more rapid in January when the earth is nearer the sun than in July when it is further away. In addition the earth's axis is inclined at an angle and thus four times a year there can be as much a differential of plus or minus 16 minutes between mean and solar time; this also means that four times a year apparent solar and mean time coincide with one another.

In order to adjust their time recording devices clockmakers of the past had no other solution than refer to the real time at noon when the sun was at its zenith. The use of a sundial was a practical way to do this, which in varying forms were commonly used until the second half of the nineteenth century when electrical power gave this valuable information. Nowadays, the speaking clock or the announcement of the time on the radio allows everyone to adjust watches and clocks anytime, day and night. The equation of time is in astronomical terms the amount to be added or subtracted in order to go from mean solar time to true solar time. Since each day has been arbitrarily divided in a 24 hours, the equation of time varies one day to the other, which can vary as much -16 to +16 each day. In adding up all those differences we can, more or less, obtain a 15 minutes variation between the real time and the mean time. Depending on the year the most significant differences are around 12th February (+14 minutes and 59 seconds) and around 3rdNovember (-16 minutes and 15 seconds). The difference is zero around 15th April, 15th June, 1st September and 24th December. It should be noted however that nowadays, because of the daylight saving time changes, we live within a two or three hour's difference, compared to solar time; our daily noon hour corresponding with the solar noon hour in central Europe. The equation of time also indicates the spring (21st-22nd March) and autumn (22nd-23rd September) equinox and the summer (around 21st June) and winter (around 21st December) solstice. The equinox is the time when the sun is aligned to the equator, which leads to an equal day and night time. The solstice is the moment when the sun is the most distant from the equator, which leads to the longest day and longest night of the year. Those dates then determine the seasons of the year.

The first to create an instrument that could indicate equation of time was Jobst Bürgi (1552-1632), pre 1600. This Swiss clockmaker, astronomer and mathematician was appointed Mécanicien to margrave Guillaume IV de Hesse-Cassel (1532-1592), clockmaker to Emperor Rodolphe II (1552-1612) and was then associated in Prague with Tycho Brahé (1546-1601) and Johannes Kepler (1571-1630). Following the introduction of the pendulum in 1656 by the Dutch scientist and mathematician Christiaan Huygens (1629-1695), clocks could be adjusted with a daily variation of a few ten or so seconds.  The question concerning the difference between real time and mean time was then raised. Scientists such as Huygens or John Flamsteed (1646-1719) wrote tables for the equation of time.

Sundials with equation were also created, for instance by the London based clockmaker Thomas Tompion (1639-1713). However it is generally considered that the oldest clock with equation of time-indicating real time and mean time was designed by the English mathematician Nicholas Mercator (1640-1687) who was a member of the London Royal Society. This was made under his supervision by the London based Flemish clockmaker Ahasuerus Fromanteel (1607-1693) circa 1666. Other scientists and clockmakers followed suit. In England they included Robert Hooke (1635-1703) and Thomas Tompion, followed by Daniel Quare (1649-1724) and George Graham (1673-1751). During the turn of the seventeenth and eighteenth centuries, Continental scientists and clockmakers were also making developments notably the abbot Jean de Hautefeuille (1647-1724), Hans Georg Enderlin de Bâle (1678-1754), Henri Sully (1680-1729), Julien Le Roy (1686-1759), Dom Jacques Alexandre (1653-1734), Charles le Bon (Born in 1678) and Antoine Thiout (around 1694-1761).

During the second half of the eighteenth and continuing into the nineteenth century, watches with equation of time started to appear. Some of the best clockmakers of this period produced both clocks and watches with equation, such as Ferdinand Berthoud (1727-1807), the brothers Lepaute, Jean-Andre (1720-1789) and Jean Baptiste (1727-1802), Jean-Antoine Lépine (1720-1814), Robert Robin (1742-1799), Abraham-Louis Breguet (1747-1823), Louis Berthoud (1754-1813), Charles Oudin (1768-1840), Nicolas-Mathieu Rieussec (1781-1852), Jacques-François Houdin (1783-1860), Henri Robert (1795-1874) and Louis-Constantin Detouche (1810-1889). At the same time British makers were also making comparable examples such as John Ellicott (1706-1772), Thomas Mudge (1715-1794) and Edward John Dent (1790-1853). More recently, during the second half of the twentieth century, the majority of watches to show equation of time have been manufactured and sold by the most prestigious workshops and brands from the Joux valley and in Geneva such as Louis Audemars (since 1811), Audemars Piguet (since 1875), Victorin Piguet (since 1880), Vacheron Constantin (since 1755) and Patek Philippe (since 1839).

Only the very best makers included equation of time and indeed only few regulators indicate this complication. Certainly the present work is of outstanding quality and complexity and should be considered among Detouche's greatest works. Every attention has been paid to detail, finish and scientific precision to create a work of both horological and aesthetic excellence.