CHRONOMETERS. 91 



chanical contrivance in the figure of the superficies 

 of the fusee, to cause the chain to be removed 

 farther from the centre of the fusee as the spring 

 grows weak, so that what is lost in the spring's 

 elasticity is gained in the. length of the lever; the 

 spring's force would always be unequal upon the 

 fusee, and thus would turn it, and consequently the 

 whole machinery, unequally. All this is remedied 

 by the conical figure of the fusee. The fusee being 

 acted upon, or put in motion, by an uniform force, 

 the great wheel, which is fixed to it, is put into 

 motion, and that drives the pinion of the centre- 

 wheel, which centre-wheel drives the pinion of the 

 third wheel, and this drives the pinion of the con- 

 trate-wheel, and this the pinion of the balance- 

 wheel, which plies the two palettes on the axis of 

 the balance, and keeps the balance in motion. 



The balance in a watch is instead of a pendulum 

 in a clock, both serving to govern the motion of 

 the whole machinery. To this balance is fixed a 

 small steel spiral spring, which regulates its mo- 

 tion, and makes it equable; whence it has its 

 name of regulator. 



It is customary for watch and clock makers to 

 call that part of the movement which is designed 

 for carrying the hands round the dial plate, the 

 watch part, or going part, in contradistinction to 

 the part of the movement which contributes to the 

 striking of the hour, which they call the clock party 

 or striking part. 



The several members of the watch parts are, 1. 

 the balance, consisting of the rim, or circular part, 

 and the verge, or spindle, to which belong two 

 palettes, or leaves, that play in the teeth of the 

 crown-wheel. 2. The potence, which is the strong 



