FUSEE. 



The action of the spring transmitted by the barrel to the chain, 

 and by the chain to the fusee, has a tendency to impart to the 

 fusee a motion of rotation in the direction of the arrows. The 

 fusee is connected with the wheel, w, by means of a ratchet-wheel 

 and catch similar to that described in the case in which the 

 moving power is a weight, by means of which the fusee F 

 imparts rotation to the wheel when it turns in the direction of the 

 arrows, but does not move it when turned in the opposite 

 direction. 



These arrangements being understood, let us suppose the key 

 applied upon the square-end G of the arbor D G of the fusee, 

 and let it be turned round in the direction contrary to that 

 indicated by the arrows. The fusee will then be turned, but will 

 ,not carry the wheel w with it ; the chain c will give to the barrel 

 B a motion of revolution contrary to the direction of the arrows, 

 the chain will be gradually uncoiled from the barrel B, and will 

 be coiled upon the spiral groove of the fusee, winding itself from 

 groove to groove, ascending on the spiral until the entire length 

 of the chain has been uncoiled from the barrel B, and coiled upon 

 ,the fusee F, as represented in fig. 15. 



During this process, the external extremity of the mainspring, 

 attached to the barrel at E, is carried round with the barrel, while 

 the internal extremity is fixed to the arbor A, which does not 

 turn with the barrel. By this means the spring is more and more 

 closely coiled round the arbor A, until the entire chain has been 

 discharged from the barrel to the fusee, when the spring will be 

 coiled into the form represented in fig. 15, and in this state the 

 intensity of its force of recoil, and the consequent tension of the 

 chain c, extended from the barrel B to the fusee E, is greatest. 



Fig. 15. 



The clock being thus wound up and left to the action of the 

 spring, the tension of the chain c, directed from the fusee to the 



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