Probably Pierre Rousseau of Pithiviers and subsequently Paris, who was the brother of André, (see lot 30), and married in 1705. 'Oignons' front the period of Louis XIV with a pirouette escapement are exceptionally rare. They are constructed on the principle of the very earliest watches to he made with balance-springs, and indeed, Huygens had in effect imagined this device to increase the amplitude of the balance which he considered to be too small. In operation, the verge staff carries not only the pallets, which engage the crown wheel in the conventional way, but also a wheel which engages a pinion on the balance staff; in effect the arc of the balance is greatly increased, and the watch appears to beat more slowly. However, the supplementary gearing for the 'pirouette' has a tendancy to increase the frictional losses and any intended gains are therefore likely to be cancelled out. Huygens quickly abandoned this stratagem, and needless to say very few examples were made. A similar oignon with "pirouette", by the same maker, is described and illustrated by A Chapiro in: La Montre Française, Editions de l'Amateur, page 96.