A fine French ‘Cosmographique’ mantel clock, Mouret, circa 1885.
Description
Equation of time
This clock is not only beautiful, but also technically interesting. The lower dial shows ‘Mean Time’, dividing a year into equal parts. The globe uses a hand to indicate where it is currently noon. Due to the shape and orbit of the earth, this ‘solar time’ deviates from ‘Mean Time’ almost throughout the entire year. This difference between Mean and Solar time is called ‘Equation of time’. Only four times a year do these two ways of measuring time correspond exactly. Outside of that, solar time runs ahead or behind with a difference of up to sixteen minutes. In the vast majority of clocks that display this difference, equation is shown by a hand that is moved by a kidney-shaped disc connected to a year calendar. The unique feature of this clock is that the equation is achieved by means of a complex differential. It is therefore not surprising that its inventor, Louis-Jérôme-Napoléon Mouret (born c.1810), was more of an engineer than a clockmaker, known for his many patents. He obtained the patent for this clock in 1976. Even at the time, the clock was considered a technical masterpiece, as evidenced by publications in scientific journals. The globe was made by ‘Maison Delamarche’ and is signed ‘Globe adopté par le Conseil de l’Université Maison Delamarche Rue Serpente 25 Paris’. In addition to national borders, the globe also shows mountain ranges and ocean currents.
Chapter ring
The 14.5-cm diameter enamel chapter ring has Roman numerals. The Breguet hands are made of blued steel.
Brocot escapement
The movement is driven by a spring barrel and has a duration of at least eight days. It is regulated by a Brocot escapement in combination with a pendulum. The back plate is signed J. Poncelet. The movement is connected to the globe’s equation mechanism. This is mounted on a plate with adjusting screws and engraved ‘J. Poncelet FABt MOREZ du JURA.’ A plaque is also attached to the plate, bearing the inscription ‘Pendule Cosmographique MOURET No. 15 BREVETE S.G.D.G.’
Annual calendar
A beveled glass disc is mounted on the mechanism, showing the months and dates. Above this annualar calendar is a globe signed ‘Globe adopté par le Conseil de l’Université Maison Delamarche Rue Serpente 25 Paris’. A fixed hand mounted on a brass bracket indicates both the day of the year and the meridian where it is currently noon. The whole is mounted on a black marble tazza-shaped base. The clock comes with a glass dome.
