COMMON THINGS CLOCKS AND WATCHES. 



the same until the clock altogether goes down. The moving 

 force of the spring, on the contrary, is subject to a continual 

 decrease of intensity. At first, when completely coiled up, its 

 intensity is greatest, but as it turns the arbor B it becomes 

 gfadually relaxed, and its intensity is continually less and less. 

 It exerts, therefore, a continually decreasing power upon the 

 wheel fixed upon the arbor, and therefore upon the hands to 

 which the motion is transmitted. 



32. As a varying power would be incompatible with that 

 uniformity and regularity which are the most essential and 

 characteristic conditions of all forms of clockwork, such a spring 

 would be quite unsuitable if some expedient were not found by 

 which its variation could be equalised. 



This has been accordingly accomplished, by a very beautiful me- 

 chanical contrivance, consisting of the combination of a flexible chain 

 and a conical barrel arranged to receive its coils, called a FUSEE. 



Fig. 14. 



This arrangement is represented in fig. 14. The mainspring is 

 attached by its inner extremity to the fixed arbor A, and by its 

 outside end at E, to a barrel B, which is capable of being turned 

 round the fixed axis A. A jointed chain is attached by one 

 extremity to the barrel at E, and being coiled several times round 

 it, is extended in the direction c, to the lowest groove of the 

 fusee E, to which its other end, e, is attached. This fusee is a 

 conical-shaped barrel, upon which a spiral groove is formed, 

 continued from the base to the summit to receive the chain. The 

 base is a toothed wheel, by which the motion imparted by the 

 mainspring and chain to the fusee is transmitted to the hands 

 through the wheelwork. The fusee is fixed upon an arbor, D G, 

 the lower end of which, projecting outside the case containing the 

 works, is formed square to receive a key made to fit it by which 

 the clock or watch is wound up. 

 24 



