WATCHES THAT RULED THE WAVES
Two of the greatest horologists of all time, Abraham-Louis Breguet and John Arnold, were friends and contemporaries, notable for making chronometers — one supplying them to La Marine Royale Française, the other to the British Royal Navy.
Marine chronometers played a crucial role in the two nations’ seafaring as they were important instruments for fleets to calculate ships’ positions.
Showcased at Baselworld 2017, Marine Équation Marchante 5887 pays tribute to Breguet’s maritime heritage with an inscription “Marine royale” on the tourbillion bar, a windrose motif adorning the barrel, and the Royal Louis, a first rank vessel in the French Royal Navy, depicted on the bridges visible through a sapphire caseback.
Besides a tourbillion and a perpetual calendar, the Grande Complication features the fascinating running equation of time that by means of two separate minutes hands simultaneously indicate civil time and true time.
As the visible motion of the Sun — the true solar time indicated on sundials — is irregular, watches and clocks thus became the basis of time. True solar time was replaced by mean solar time, corresponding to civil or standard hours and minutes, within which each day has the same duration of exactly 24 hours.
On just four days a year, the two times are exactly the same. The discrepancy between mean solar time and true solar time then ranges from minus 16 to plus 14 minutes.
The equation of time is one of the rarest horological complications, which serves to display this difference between mean solar time and true solar time.
Given that the Sun’s various positions in the sky are reproduced in an identical manner on the same dates, watchmakers can “programme” them by means of a special cam, and mechanically reproduce the path of the Sun’s successive positions, called an analemma curve.
Breguet has technically taken the equation of time to the next level by developing its Marine Équation Marchante 5887 with a running solar hand adorned with a golden sun that provides a direct reading of solar-time minutes.
Requiring an arduous construction process, it must sweep in a conventional way around the dial, like the civil minutes hand, while also daily moving away from the latter by a distance that varies in accordance with the analemma curve, in order to display the equation.
The Swiss watchmaker accomplished this by equipping the running solar hand with a differential gear powered by two rotation sources operating entirely independently: the rotation of civil minutes, and that controlled by the lever in contact with the equation of time cam, which makes one full turn per year.
In addition, an extremely slim equation cam borne by a transparent sapphire disc also serves to correct the equation of time by month.
The running equation of time complication is naturally complemented by the perpetual calendar. The days of the week as well as the months and the leap-year cycle are displayed through two apertures — one between 10 and 11 o’clock and the other between 1 and 2 o’clock.
The date appears inside the chapter ring by means of a retrograde hand tipped with an anchor motif and sweeping across an arc running from 9 to 3 o’clock.
The third complication, a 60-second tourbillion, has a titanium carriage housing a Breguet balance with a silicon balance spring that enables the balance wheel to achieve a 4Hz frequency, while maintaining an 80-hour power reserve displayed in an aperture between 7 and 9 o’clock.
Besides the technical complexity, artisanal skills are features in the front dial, whose two types of engine-turning pattern were specifically created for this 43.9mm timepiece.
Available in two variations, the Grande Complication in rose gold has a silvered dial and an anthracite movement while the platinum interpretation has a blue dial and a rhodium-plated movement.