French Louis-Philippe period floorstanding regulator (circa 1840) of small size and shallow depth, signed "Chronomètre, système JAROSSAY" on the dial, and "Jarossay à Paris" on the graduated levelling brass plate situated below the pendulum. Mahogany veneered and mahogany case, plain base and removable top plinth, hiding the winding mechanism. Dial with Roman numerals and very fine micrometric graduation with Arab numerals marking the five minutes, allowing for accurate time reading with a very precise hour hand only, a sweeping seconds hand has its own smaller dial below XII.
High precision movement with Graham dead-beat escapement with low amplitude, the force provided with a weight and counterweight hung with an endless rope through a system of six pulleys (2 mobile and 4 fixed).
Large polished brass pendulum bob hung by a oval-section steel pendulum rod with precise regulation below.
The temperature compensation is achieved through a highly unusual and simple system: a second rod identical to the pendulum's is fixed from the bottom and pushes a lever that will in turn indirectly increase the pendulum's length when the temperature rises.
H : 73" (185 cm) ; W: 15 ¼" (39 cm) ; D: 6 ½” (16,5 cm)
The Parisian clockmaker Louis-Antoine Jarossay (1780-1859) was the son of Urbain Jarossay, also clockmaker in Paris for the Comte d'Artois. The latter installed the turret clock of the Saint-Germain-des-Prés church on behalf of Jean-André Le Paute (1720-1789) in 1781.
Louis-Antoine Jarossay was renowned for his ability to make high quality domestic regulators and is often recognised as one of the more inventive clockmakers of the 19th Century. He is also known to have used endless screw gears in horology, a technology that he studied in depth.
He patented the double-mainspring pulley in 1844 and the use of wormscrews in 1850. This latter invention allowed him to substantially reduce the costs of manufacture without sacrificing quality nor precision.
Tardy, Dictionnaire des horlogers français ; The Art of Horology in France, catalogue Antiquorum 1993.