Louis Moinet Compteur de Tierces (Circa 1815) – The First Mechanical Chronograph Ever Made

Created in 1816 by the legendary master watch maker Louis Moinet, the “compteur de tierces” is considered as the first mechanical chronograph ever made.Recently one such piece was discovered and according to hallmarks on the dust cover, the chronograph was started in 1815 and completed the following year.

This remarkable instrument of an entirely original design is evidently the work of a genius well ahead of his time. It measures events to the sixtieth of a second (known in those days as a “third” or tierce in French), indicated by a central hand. The elapsed seconds and minutes are recorded on separate subdials, and the hours on a 24-hour dial.

The stop, start and reset functions for the central hand are controlled by two buttons which qualifies it as a chronograph in the modern sense, although the term was coined much later. The return-to-zero function was revolutionary for the time. Until today, this invention had been thought to date from Adolphe Nicole’s patent of 1862.

In the 19th century, watchmakers sought to increase the precision with which they could measure time by increasing the frequency of their watches. By 1820 the generally accepted limit was time measurement to the tenth of a second.

Moinet’s compteur de tierces (“thirds timer”) was thus by far the most precise instrument of its period, measuring time six times more closely than the norm. Moinet’s division of time into sixtieths of a second is another historical achievement that places him among the great contributors to modern watchmaking.

The chronograph’s balance beats at 216,000 vibrations an hour or at the then unimaginable frequency of 30Hz. To put that into perspective, the usual balance frequency in a modern wristwatch is 28,800 v/h or 4Hz. Louis Moinet is thus the father of high-frequency time measurement, although it was not until exactly a century later that a watch was made to beat his record.

Moinet made the timer for an astronomical transit instrument, originally mounted for use at sea, that he had adapted to track the movement of heavenly bodies from the land.  Why did Moinet need such high frequency? He was timing the passage of stars, planets and even planetary moons. A frequency of 216,000 v/h imparted 60 vibrations a second, thus dividing the second into sixtieths. He made the compteur initially to set the precise distance between the crosshairs in his telescope.

Moinet’s compteur had to function for at least 24 hours at an energy-hungry frequency to time successive transits of a star. To minimise energy consumption his escapement ran on oiled rubies. He reported that it had worked very well for a prolonged period.

Technical details

THE LOUIS MOINET CHRONOGRAPH

Movement
Full plates between four pillars, barrel and fusee
Ruby and steel cylinder escapement
Foliot balance with platinum adjustment weights
30-tooth escape-wheel
Flat balance spring with seven coils
Six pierced ruby bearings with endstones making a total of 13 jewels with the ruby cylinder
Made in gilt and frosted brass
Frequency: 216,000 vibrations an hour, 30Hz

Dimensions
Diameter: 57.7mm
Height:  9mm
Signed on the upper plate: Louis Moinet

Power reserve
More than 30 hours
State of wind indicator visible through an aperture in the dust cover

Case
Silver with a rim around the bezel and caseback
Bezel with a bayonet fixture
Hinged dust cover, locked by a threaded stud
Four-part semi-bassine case with flat caseband

Four hallmarks on the dust cover:
1. Association des Orfèvres de Paris (goldsmith’s guild);
2. Master’s mark;
3. Second rooster (Ag 900);
4. Guarantee No 815.

Dial
Silvered and frosted metal, signed Louis Moinet
Three subdials on the face:
Top left: 60-minute counter
Top right: 60-second counter
Bottom centre:     24-hour counter

Hands
Slender, counterpoised centre hand for the 60ths of a second
Two identical hands for the seconds and minutes counters
An open-tip hand for the hours
All the hands are in blued steel

Controls
At 12 o’clock: button to start and stop the chronograph
At 11 o’clock: button to return the 1/60 seconds hand to zero.

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