Exceptional Horological Works of Art

Geneva, Oct 19, 2002

LOT 54

Brosse à Bordeaux (France), No 24, circa 1830. Very fine and unusual 2-day marine chrono-meter of special construction.

CHF 18,000 - 22,000

EUR 12,000 - 14,000

Sold: CHF 20,700

C. Two-body, mahogany, top with sliding panel to reveal the dial, fixed brass handles, lock in front, bracket for key in the left rear corner. Gimbaled bowl with poising weight at the bottom, threaded glazed bezel. D. Silvered, champlevé Roman numerals, outer minute track, subsidiary seconds. Blued steel "spade" hands. M. 96 mm, brass, 3/4-plate, going barrel, Earnshaw spring detent chronometer escapement, unusual cut bimetallic compensation balance with brass arm and bimetallic rims screwed to the arm bracket, Earnshaw-type trapezoidal sliding temperature weights, two mean-time screws, blued steel free-sprung helical balance spring with terminal curves fastened to adjustable stud. Signed on the dial. Dim. 20 x 20 x 18 cm.


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Grading System
Grade: AAA

Excellent
Case: 3

Good
Movement: 3*

Good

Overhaul recommended, at buyer's expense
Dial: 3 - 01

Notes

This is one of only three Brosse marine chronometers known. Each one is highly unusual. The one sold by Antiquorum on April 12, 1997 (lot 231), features the most unusual constant force escapement. The present one and the one in the Musée des Arts et Métiers are very similar, the only significant difference being that this one is equipped with an Earnshaw spring detent and the one at the Musée des Arts et Métiers with Arnold?s spring detent escapement. All three are with going barrels. The concept of timepieces with just going barrel appeared in France in late 1670 or early 1680. The invention by Huygens in 1675 of the balance spring, with its consequent isochronism, met with a great deal of enthusiasm. Many fine watchmakers hoped that the regularity of the balance?s oscillations might suffice to render the equalizing function of the fusee unnecessary, thus lowering, among other things, production costs. This hope led to a certain number of trials. It appears that verge watches without fusee originated in Paris (Balthazar, Martinot, Gribelin, Thuret, Champion) and then spread to Rouen, via watchmakers such as Gloria. In England Tompion tried it at east once. In the 1830?s the tendency reappeared among French chronometer makers. Louis-Clément Breguet, the grandson of Abraham, seems to be the one who started the new trend. There are numerous examples of this construction in his pieces (e.g. see No. 4851 made in 1831, Antiquorum, The Art of Breguet, lot 86). His register is full of entries mentioning marine chro-nometers with a single barrel. They had a slightly different mainspring with a thicker end (already suggested by Pierre Le Roy in 1760?s). Others fol-lowed suit, among them Brosse. In this chronometer he employed another unusual feature, the balance. Unlike typical balances with steel arm, Brosse em-ployed a brass arm, possibly experimenting with Mid-dle Temperature Error. There are only fourteen known Brosse pieces, five at the Musée des Arts et Métiers, three at this sale, four sold by Antiquorum: April 12, 1997 (lot 231), April 21, 1990 (lot 397), November 11, 2001 (lot 52 a +b) and two in a private collection. His entire production was probably about 30 or 40 pieces. All are unusual; Brosse?s peers always praised his ingenuity and the high quality of his execution.