Excluding the balance and the balance spring, this chronometer is absolutely identical to those of Henri Motel's late production. Its mainspring carries the signature of Bourquin and the date 1846 like those of chronometers No. 261 and 263, which were respectively sold by Motel to the Dépôt de la Marine on February 12, 1850 and December 31, 1850. It is therefore indeed the chronometer No. 262, sold to the Dépôt de la Marine on June 1, 1849, on which the signature of Motel was clearly removed frothe dial (hammered on the reverse) and replaced on the movement by that of H. Charbonnier.Please refer to J.C. Sabrier: La Longitude en mer à l'heure de Louis Berthoud et de Henri Motel, Antiquorum Editions, Geneva, 1993, pp. 646, 650 and 660. See also Motel chronometer No. 267,p. 612, fig.156.Poole's Auxiliary Compensation.This is the first form of auxiliary compensation known to have been applied to a compensation balance.In its simplest form, which has been used in a large number of chronometers, it consists simply of two small screws carried upon rigid arms united to the cross-bar of the balance, and so adjusted as to meet the rims, near their roots, as they move outwards in low temperatures. The effective lengths of the latter (and accordingly, the motion of the weights which they carry) is thus reduced slightly below its normal amount. This action is made use of by adjusting the chronometer fitted with such abalance to keep correct time, say at 90° and 60°, which would normally cause it to have a considerably increased error at 30°. The action of the check screw, however, counteracts this.The practical effect of the device is then, to halve the middle temperature error between the two standard temperatures, and greatly to reduce the error which would normally be produced in low temperature by this adjustment. Balances of this pattern are simple to make, and their popularity may be ascribed to this reason.Joseph-Tadeus Winnerl was born at Murech (Austrian Styria) on 25 January 1799. It is not known where he carried out his apprenticeship. He left his country when very young to visit the principal cities of Europe in which clockmaking was practised. Thus he worked for Kessel in Altona, and Jürgensen in Copenhagen. He arrived in Paris in 1829, where he was employed by the best clockmakers, in particular Breguet. He chose France as his adopted country and was naturalised.Toward 1832 he set up shop in the passage de Lorette in Paris, and established a workshop there for making marine chronometers.At the Exhibition of the Products of French Industry in 1839, the Central Jury awarded him a Gold Medal.In 1843 he presented to the Société d'Encouragement (Society for the Encouragement of the Arts and Sciences) an anchor escapement modified for clocks, which was the subject of a report by Baron Seguier. In the same year he presented to the same society a split second recorder that he had invented.At the 1844 Exhibition, the Central Jury awarded him an addition to the Gold Medal that he had already obtained in 1839, and he was appointed a Chevalier de la Légion d'Honneur.At the Universal Exhibition of 1855, the Jury awarded him a Grand Prix, and he was raised to the rank of Officier de la Légion d'Honneur.Appointed clockmaker to the Paris Observatory in 1850, he presented a Mémoire sur les pendules de précision to the Society of Paris Clockmakers in 1857, as well as another entitled: Règle de la construction de l'échappement duplex et modification de cet échappement pour l'appliquer aux montres à roues de rencontre.Elected Councillor of the City of Paris in 1859, he was successively re-elected until 1870, when he sold his business.Appointed Horloger Expert de la Marine by ministerial decision of 17 November 1873, he kept this office until his death.In 1876, he presented to the Academy of Science a compensated pendulum for chronometers, with a mechanism for correcting secondary errors at intermediate temperatures.Winnerl died on 25 January 1886, at Andresy, a small town in the Seine-et-Oise, where he had settled soon after closing his business. His funeral oration was pronounced by Mr. Caspari, Ingénieur en Chef du Service Hydrographique.His work consists of about 550 marine chronometers, pocket chronometers, split second recorders, and astronomical long case clocks of which two had been made for the Paris Observatory, and two for the Navy Depot. To this list should be added a large number of mantelpiece clocks, and watches, made at the request of collectors of fine clockwork.