Page 22 of Souveraine Collection by F.P.Journe

the constant-force device from ancient times humankind has constantly attempted to measure time by dividing it into equal fractions and inventing the notion of isochronism only with the arrival of the first mechanical clocks did specialists begin to seek a means of equalising the force reaching the escapement the balance-spring did not yet exist and the so-called foliot balance had an irregular beat due to the arrival of a force varying because of the imperfections of the gearing at the time clocks were equipped with just one hand which completed a revolution once every 12 hours since their degree of imprecision did not permit the measurement of minutes after the invention of the mainspring which would enable the construction of table-clocks 15th century watchmaker jobst bürgi had the idea of adding an extra gear representing an independent system wound in short spurts by the mainspring the escapement thus ensured a more constant flow and enabled an autonomy of several months this was the first remontoire or constant-force device later 17th century dutch watchmaker christiaan huygens invented the balance-spring and the pendulum these innovations would give both clocks and watches an unprecedented degree of precision timekeeping the minute hand became widespread and the constant-force device fell into oblivion for around a century with the arrival of the 18 th century known as the age of enlightenment the high requirements relating to astronomical observations and calculations of longitude for maritime navigation called for ever higher levels of precision as new technical solutions were found the seconds hand became a common feature on watches of the period in england thomas mudge invented a constant-force device for the h.3 marine chronometer while famous french watchmaker robert robin ­ watchmaker to the king ­ also invented one for his precision regulators pardoxically it was in the 19th century that the constant-force device became widely used in the construction of clocks intended for buildings ­ not to remedy any flaws in the springs since all these clocks ran by driving-weights but to isolate the time mechanism from the outside hands this was because the latter were exposed to strong winds and might disturb the mechanism nonethless making a constant-force device was a complex and tedious task causing it to be almost entirely abandoned in the 20 th century apart from a few rare exceptions english watchmaker georges daniels used it in a tourbillon pocket-watch his contemporary anthony randall built it into a table-clock based on the principle of john harrison s h.4 and i myself have incorporated it into three tourbillon pocket-watches a so-called sympathique clock and more recently for the very first time in wristwatch form with the first model in the f.p.journe ­ invenit et fecit ­ collection the tourbillon souverain what is fascinating in the principle of the constant-force device is that each watchmaker who has set out to build one has his own personal interpretation only the basic idea remains the same françois-paul journe 71

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