MECHANISM OF A WATCH. 



If the fusee, which is omitted in this figure, were introduced, 

 it would occupy the place of the spring, and would be turned by 

 the axle imparting a like revolution to the axis of the spring by 

 means of the chain. 



When the watch is wound up, the re -action of the spring, 

 rendered uniform in its force by the fusee, imparts a motion of 

 revolution to the ratchet-wheel B, in the direction of the arrow. 

 By this motion the tooth of the ratchet-wheel in which the point 

 o of the catch is engaged, presses against the catch so as to carry 

 it round with it in the direction of the arrow ; but the catch being 

 attached to the face of the wheel c, at n, this wheel is carried 

 round also in the same direction, and with a common motion. 



The teeth of the wheel c act in those of the pinion d, which 

 is fixed upon the axle d D. Upon the same axle is fixed the 

 wheel D, so that the wheel D and the pinion d receive a com- 

 mon motion of revolution from the wheel c. 



The wheel D, in precisely the same manner, imparts a common 

 motion of revolution to the pinion e, and the wheel E ; and the 

 wheel E imparts a common motion of revolution to the pinion f 

 and the wheel F. 



This last wheel F is of the form called a crown-wheel, and 

 acts upon the pinion </, imparting to it, and to the escapement 

 wheel G, a common motion of revolution. This escapement- 

 wheel is acted upon and controlled by the pallets or other con- 

 trivances attached to the axis of the balance-wheel H, so as to 

 regulate its motion by the oscillations of that wheel in the same 

 manner as the escapement- wheel of a clock is regulated by the 

 anchor of the pendulum. 



It may be asked why so long a series of wheels and pinions are 

 interposed between the mainspring and the balance-wheel? and 

 why the first pinion d may not act directly upon the escapement- 

 wheel ? The object attained by the multiplication of the wheels 

 and pinions is to cause the mainspring, by acting through a small 

 space, to produce a considerable number of revolutions of the 

 escapement- wheel, for without that the spring would be speedily 

 relaxed, and the watch would require more frequent winding up. 

 Thus by the arrangement here shown, while the mainspring 

 causes the wheel c to revolve once, it causes the pinion d and 

 the wheel D to revolve as many times as the number of teeth 

 in c is greater than the number in d. Thus if there are ten 

 times as many teeth in c as in d, one revolution of c will produce 

 ten of d and i>. In like manner if D have ten times as many 

 teeth as e, one revolution of D will produce ten of e and E, and 

 so on. In this way it is evident that one revolution of the first 

 wheel c, which is on the axis of the fusee, can be made by the 



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