378 NATURAL THEOLOGY. 



fusee correspond with the diminished power of 

 the spring as it uncoils. The spring exerts the 

 greatest force when it begins to uncoil itself, and 

 this force is diminished as it relaxes. To correct 

 this inequality, the fusee is formed. It is an axle 

 so contrived that, with the varying power, the 

 motion shall be uniform, and for this purpose it 

 has the form of a truncated cone with a spiral 

 groove which receives the chain. When the 

 spring is acting with the greatest intensity, the 

 chain pulls on a part of the fusee, not much re- 

 moved from the centre of its revolution, and 

 therefore with a small leverage ; but when the 

 spring acts feebly, as the spiral groove becomes 

 further and further removed from the axis of the 

 fusee, the chain is uncoiled from it with a greater 

 lever power. 



The great wheel on the base of the fusee 

 checks into leaves of the pinion of the second or 

 central wheel, and that moves, in succession, the 

 third and fourth wheels. But before we estimate 

 the effects of the respective wheels and pinions, 

 we shall pass to the scapement, or balance. 



The effect of the scapement is to preserve the 

 moving power, or " sustaining force," uniform, to 

 equalize the effect of the spring on the work ; for 

 although this is in part effected through the fusee, 

 it is not done sufficiently. 



It is interesting and improving to observe, in 

 the history of philosophy, how occurrences the 

 most familiar become important when applied by 



