Important Watches Wristwatches, and C...

Geneva, Hotel Des Bergues, Apr 02, 2000

LOT 46

L. Leroy & Cie. No. 1001, circa 1910.Fine and rare mahogany, Decimal Time Tropomètre with power reserve indicator.

CHF 10,000 - 12,000

C. Three-body mahogany deck watch box, the brass bowl with screwed bezel. D. Silvered with Arabic ring for the 40 decimal hours and outer ring for the decimal minutes, subsidiary dial for 25 decimal seconds and half-moon sector for 63 decimal hours, power reserve indication. Gilt brass hands. M. Gilt brass full plate with slightly tapered turned pillars, fusee with chain and maintaining power, Earnshaw type spring detent escapement, two-arm compensation balance with cylindrical poising weights ad timing screws, free sprung helical paladium balance spring with terminal curve, diamond end-stone.Signed on the box, dial and back plate.Dial diam. 70 mm.


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Grading System
Grade: AAA

Excellent
Case: 3

Good
Movement: * 3
Dial: 3 - 01

Notes

Accompanied by photocopies of an article explaining the functions of the so-called Tropomètres.Such chronometers were used for calculation on geographic maps. Only 9 of these Tropomètres were commissioned to Leroy by the French Army.TropomètresTropomètres were devised by Mr. Ditisheim according to the decimal time as promoted by M. de Rey-Pailhade. The extension of the decimal time, by means of the division of a quarter of a circle, applied to navigation was experimented and published by M. le Commandant Guyou. It requires a decimal marine chronometer, an ephemeris timetable and nautical tables, a map with decimal division and a decimal sextant.Thanks to the decimal system, nautical calculations are greatly simplified. The navigator only needs to determine the elevation of the sun by means of the sextant to be able to find its position on the map with decimal divisions. The tropomètre has first to be adjusted to indicate 0 for noon at the Paris mean time. As it is beating 20?000 times a day, each beat is of 0? 432 which equals to 2 milligrades on the map, which in turn corresponds to 200 metres on the equator line.