Pierre Le Roy
Encyclopedia
Pierre Le Roy was a French
clockmaker
. He was the inventor of the detent escapement
, the temperature-compensated balance
and the isochronous balance spring
. His developments are considered as the foundation of the modern chronometer
. Le Roy was born in Paris
, eldest son of Julien Le Roy
, a clockmaker to Louis XV who had worked with Henry Sully
, in which place Pierre Le Roy succeeded his father.
He was distinguished principally in his mastery and improvement of the chronometer
and chronograph
, above all of the marine chronometer
, in which he carried forward the pioneering work of John Harrison
. He took a different approach from that of Harrison, believing that the way to achieve seaworthiness was to detach the escapement from the balance. He also differed from Harrison regarding his temperature compensation method, which used the variation of the rotation radius of the balance by modifying the diameter of the balance through bi-metallic components, a method which would become a standard in chronometers. His technique for temperature compensation was highly efficient in that it worked without changing the length of the spiral balance spring, which he had discovered to be isochronous
only at a precise given length (i.e. when frequency is independent of amplitude, so that a mechanical clock or watch
runs at the same rate regardless of changes in its drive force, so it keeps correct time as the mainspring
unwinds).
balance spring, innovations which would be adopted in subsequent chronometers. Harrison showed the possibility of having a reliable chronometer at sea, but these developments by Le Roy are considered as the foundation of the modern chronometer. Pierre Le Roy's chronometer had a performance equivalent to that of the Harrison H4 chronometer.
In 1769 he was awarded the double prize offered by the Académie française
for the best method of measuring time at sea. He succeeded in giving his instruments the greatest possible regularity by the discovery of the isochronous spiral spring, in which he was in competition with Ferdinand Berthoud
, but which he published first.
He was the author of several valuable publications on the art and science of clock-making and chronography, among them the Étrennes chronométriques of 1760. He also became Horloger du Roi in 1760.
The work of Le Roy was not fully recognized in France however, and his contemporary Ferdinand Berthoud
became more famous, obtaining the prestigious title of Horloger de Marine, which left Le Roy desillusioned and led him to retire. He died in Vitry
in 1785.
French people
The French are a nation that share a common French culture and speak the French language as a mother tongue. Historically, the French population are descended from peoples of Celtic, Latin and Germanic origin, and are today a mixture of several ethnic groups...
clockmaker
Clockmaker
A clockmaker is an artisan who makes and repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly to repairing clocks and watches...
. He was the inventor of the detent escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
, the temperature-compensated balance
Balance wheel
The balance wheel is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral spring, the balance spring or hairspring...
and the isochronous balance spring
Balance spring
A balance spring, or hairspring, is a part used in mechanical timepieces. The balance spring, attached to the balance wheel, controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands...
. His developments are considered as the foundation of the modern chronometer
Chronometer
Chronometer may refer to:* Chronometer watch, a watch tested and certified to meet certain precision standards* Hydrochronometer, a water clock* Marine chronometer, a timekeeper used for celestial navigation...
. Le Roy was born in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
, eldest son of Julien Le Roy
Julien Le Roy
Julien Le Roy was a major 18th-century Parisian clockmaker and watchmaker.He was born in Tours in 1686, and by the age of 13, had already made his first clock. In 1699, he moved to Paris for further training. He became maitre horloger in 1713 and later juré of his guild...
, a clockmaker to Louis XV who had worked with Henry Sully
Henry Sully
Henry Sully was an English clockmaker. He lived for many years in France.-Marine clock:He invented a marine clock to determine longitude accurately, a sophisticated pendulum clock. He presented a first Montre de la Mer in 1716 to the French Académie des Sciences. He was the first to develop...
, in which place Pierre Le Roy succeeded his father.
Invention of the detent escapement
In 1748, he invented a pivoted detent type of escapement, or detached escapement, which makes him the inventor of the detent escapement: "The invention of the detached escapement belongs to P. Le Roy".He was distinguished principally in his mastery and improvement of the chronometer
Chronometer
Chronometer may refer to:* Chronometer watch, a watch tested and certified to meet certain precision standards* Hydrochronometer, a water clock* Marine chronometer, a timekeeper used for celestial navigation...
and chronograph
Chronograph
A chronograph is a timepiece or watch with both timekeeping and stopwatch functions as well as other functions. Pocket watch chronographs were produced as early as the 18th century but did not become popular until the 1820s...
, above all of the marine chronometer
Marine chronometer
A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...
, in which he carried forward the pioneering work of John Harrison
John Harrison
John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...
. He took a different approach from that of Harrison, believing that the way to achieve seaworthiness was to detach the escapement from the balance. He also differed from Harrison regarding his temperature compensation method, which used the variation of the rotation radius of the balance by modifying the diameter of the balance through bi-metallic components, a method which would become a standard in chronometers. His technique for temperature compensation was highly efficient in that it worked without changing the length of the spiral balance spring, which he had discovered to be isochronous
Isochronous
Isochronous : From Greek iso, equal + chronos, time. It literally means regularly, or at equal time intervals. In general English language, it refers to something that occurs at a regular interval, of the same duration; as opposed to synchronous which refers to more than one thing happening at the...
only at a precise given length (i.e. when frequency is independent of amplitude, so that a mechanical clock or watch
Watch
A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...
runs at the same rate regardless of changes in its drive force, so it keeps correct time as the mainspring
Mainspring
A mainspring is a spiral torsion spring of metal ribbon that is the power source in mechanical watches and some clocks. Winding the timepiece, by turning a knob or key, stores energy in the mainspring by twisting the spiral tighter. The force of the mainspring then turns the clock's wheels as it...
unwinds).
Development of the modern marine chronometer
After having designed plans in 1754, he constructed his first chronometers by 1756, and accomplished his masterpiece in 1766. This remarkable chronometer incorporated a detached escapement, a temperature-compensated balance and an isochronousIsochronous
Isochronous : From Greek iso, equal + chronos, time. It literally means regularly, or at equal time intervals. In general English language, it refers to something that occurs at a regular interval, of the same duration; as opposed to synchronous which refers to more than one thing happening at the...
balance spring, innovations which would be adopted in subsequent chronometers. Harrison showed the possibility of having a reliable chronometer at sea, but these developments by Le Roy are considered as the foundation of the modern chronometer. Pierre Le Roy's chronometer had a performance equivalent to that of the Harrison H4 chronometer.
In 1769 he was awarded the double prize offered by the Académie française
Académie française
L'Académie française , also called the French Academy, is the pre-eminent French learned body on matters pertaining to the French language. The Académie was officially established in 1635 by Cardinal Richelieu, the chief minister to King Louis XIII. Suppressed in 1793 during the French Revolution,...
for the best method of measuring time at sea. He succeeded in giving his instruments the greatest possible regularity by the discovery of the isochronous spiral spring, in which he was in competition with Ferdinand Berthoud
Ferdinand Berthoud
Ferdinand Berthoud was a Swiss chronometer-maker.-Career:He was born at Plancemont, Neuchâtel, Switzerland. Having served his apprenticeship with his brother, Jean-Henri, a pendulum maker, he set up a clockmaking business in Paris in 1745 and gained a great reputation for the excellence and...
, but which he published first.
He was the author of several valuable publications on the art and science of clock-making and chronography, among them the Étrennes chronométriques of 1760. He also became Horloger du Roi in 1760.
The work of Le Roy was not fully recognized in France however, and his contemporary Ferdinand Berthoud
Ferdinand Berthoud
Ferdinand Berthoud was a Swiss chronometer-maker.-Career:He was born at Plancemont, Neuchâtel, Switzerland. Having served his apprenticeship with his brother, Jean-Henri, a pendulum maker, he set up a clockmaking business in Paris in 1745 and gained a great reputation for the excellence and...
became more famous, obtaining the prestigious title of Horloger de Marine, which left Le Roy desillusioned and led him to retire. He died in Vitry
Vitry
Vitry is part of the name of several communes in France:* Vitry-aux-Loges, in the Loiret département* Vitry-en-Artois, in the Pas-de-Calais département* Vitry-en-Charollais, in the Saône-et-Loire département...
in 1785.