HOROLOGY. 





the centre-wheel pinion : this centre pinion, with 

 the centre wheel or second wheel D', turns once 

 in an hour. The centre wheel D' works into the 

 third-wheel pinion E ; and on the same arbor is 

 E', the third wheel, which gives motion to the 

 fourth or centrate-wheel pinion G, and along with 

 it the centrate-wheel G'. The teeth of this wheel 

 are placed at right angles to its plane, and act on 

 the pinion H, called the balance-wheel pinion ; H' 

 being the balance-wheel, or scape-wheel, or crown- 

 wheel, attached to the same arbor. The balance- 

 wheel acts on the two pallets, p, p, attached to the 

 verge or arbor of the balance K ; and these being 

 placed at a distance from each other, equal to the 

 diameter of the balance-wheel, and in different 

 places, receive alternately from the scape-wheel an 

 impetus in opposite directions, which keeps up 

 the vibratory motion of the balance. Such is the 

 general arrangement of the powers and motions ; 

 we shall now proceed to the analysis. 



Mainspring and Fusee. 



The invention of the mainspring, in place of the 

 weight, was the first pre-requisite to the formation 

 of the watch. But although the mainspring was 

 applied as the maintaining power to time-pieces of 

 a very imperfect description, called watches, about 

 the middle of the sixteenth century, and although 

 the balance had, in such instruments as these, 

 assumed its present form of a vibrating ring, with 

 the greatest weight of course accumulated round 

 a circumference, it was not until the spiral hair- 

 spring was applied to the balance, some time after 

 the invention of the pendulum, as a substitute in 

 clocks for the balance itself, that a comparatively 

 useless machine was converted into a time- 

 measurer nearly as accurate, even in its ordinary 

 form, as the pendulum-clock. Though the inven- 

 tion of the balance-spring, however, was compara- 

 tively an early improvement, and the greatest the 

 watch has ever received, we must pass it over in 

 the meantime, till we briefly describe those parts 

 of the mechanism which first rendered the exist- 

 ence of the watch possible at all. 



The mainspring consists of a coil of thin elastic 

 steel ribbon, inclosed in a miniature barrel or 

 ' drum,' to the inner side of which the outer end 

 of the coil is fixed, while 

 the inner is fixed to an 

 axis at the centre of 

 the drum, round which 

 it may be wound or 

 twisted, so as, by its 

 elasticity and recoil, to 

 cause the drum to make 

 as many revolutions as it makes turns itself while 

 it unwinds. Here, then, we have the main power 

 which sets the whole mechanism of the watch in 

 motion. But it is evident that this power, if thus 

 at once applied to the wheels, would cause them 

 to move with less and less rapidity as it became 

 uncoiled, and as its springing power of course 

 became exhausted ; so that unless the wheels were 

 so constructed that only the middle turns were 

 required to be in action, and not those in which 

 it is at its greatest or its least power, a force suffi- 

 ciently equal even for ordinary purposes could not 

 be thus obtained. French spring-clocks, strange 

 to say, are still, in general, made on this defective 

 principle ; but English watches and spring-clocks 



are supplied with a 'fusee,' which corrects the 

 inequalities of the mainspring with a simplicity 

 only equalled by its ingenuity. 



The fusee, F, is a cone with a spiral groove, 

 attached to the side of the first wheel of the watch, 



and connected with the barrel or drum B, contain- 

 ing the mainspring, by a chain C, hooked, at its 

 ends, to both. 



In winding a watch, the key is placed on the 

 axis of the fusee, and the chain is wound off the 

 barrel on to the cone of the fusee. When fully so 

 wound, the spring is at its greatest power of recoil ; 

 but the chain being then round the smallest part 

 of the cone, the influence of the spring on the 

 wheels is at its least amount ; while, just as the 

 power of the spring relaxes and diminishes, the 

 cone enlarges, and its lever-influence hence in- 

 creases. The fusee, in short, is a variable lever, 

 worked by the mainspring, with more purchase 

 when it has less power, and with less purchase 

 when it has more power. It is a very beautiful 

 contrivance, completely answering the intended 

 purpose, when properly made. By means of a 

 spring contained in the interior of the fusee-wheel, 

 the watch is maintained in motion, while the fusee 

 itself is turned by the watch-key in winding up 

 the mainspring. This is called the going fusee. 

 When the watch or spring-clock has no fusee at 

 all and in very flat watches no fusee can be intro- 

 duced the barrel is immediately attached to the 

 first wheel. In every case, however, the power of 

 the spring is conveyed through the wheels, by 

 nearly the same arrangement in all watches and 

 clocks, to 



The Escapement 



On the peculiar construction of this part of the 

 mechanism, so as best to keep up the vibrations 

 of the balance, the superiority of one watch over 

 another principally depends. The vertical escape- 

 ment, represented in 

 the adjoining figure, 

 is liable, though in 

 a less degree, to the 

 same objection as 

 the old crown-wheel 

 and the crutch or 

 anchor escapements 

 in clocks. There is 

 a recoil of the scape-wheel after one of its teeth 

 has been stopped by a pallet, which interferes 

 more or less with the accuracy and uniformity of 

 the motion of the train. 



Almost immediately after the invention of the 

 balance-spring, attempts began to be made to 

 introduce an escapement which would produce 

 greater accuracy than the vertical escapement 

 Hooke, Hiiygens, Hatitefeuille, and Tompion in- 

 troduced new principles, each of which has since 

 been successfully applied, though they all, from 

 imperfect execution, failed at the time. The first 



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