Fuzee
A brass cone, as shown in Figure 136, having a spiral groove cut on it to hold the chain, and interposed between the barrel and center pinion of a watch for the purpose of equalizing the pull of the mainspring and converting it into a constant force. The pull of the mainspring is greater when wound around the barrel arbor than when it has expanded to the circumference of the barrel. The principle of its construction is that by winding the fuzee chain upon its cone the mainspring is wound, and the greatest pull comes upon the smaller end of the cone, and as the pull becomes less by the unwinding of the mainspring, the leverage (by means of the chain unwinding from a smaller to a larger cone) increases, and the rate of its increase constitutes a perfect adjustment of the mainspring. The fuzee chain was first introduced by Gruet of Geneva in 1664. The fuzee is held in great esteem by English watchmakers, and possesses many excellent points, although not employed in any American made watch.
Saunier says "The power of selecting the best series of turns to include within the limits of the stopwork is so important that it must be regarded as the reason for the retention of the fuzee in chronometers; because with the fuzee we can secure with certainty a rather longer period of going and a mainspring the uncoiling of which takes place under the best possible conditions. This last observation is of the highest importance, so much so that it alone should settle the discussion between the advocates of the fuzee and of the going barrel. It explains why pocket chronometers, unless they have enormous barrels, cannot do without a fuzee. It justifies the English makers, who in their splendid high-class watches, with such excellent rates, have retained it; but they make an error when they put it in watches of the commoner class." Glasgow says, "Considering the great ease with which an ordinary marine chronometer mainspring with a fuzee can be perfectly adjusted, without any chance of resistance from adhesion or clustering, it seems strange that these men (refering to Jurgensen and Robert), who were so well acquainted with the superiority of the fuzee, should have devoted so much time to experiments with going barrel chronometers, and it is a question whether this persistence in trying to supercede the fuzee adjustment in marine chronometers has not lost this branch of the trade to France." Glasgow further says, "Notwithstanding the growing disposition amongst modern English watchmakers to praise and adopt that going barrel, all the old French watchmakers and writers on the subject agree as to the superiority of the fuzee and the tapered mainspring with a rigid attachment to the barrel."