COMMON THINGS CLOCKS AND WATCHES. 



flat watches, in all of which the adoption of the cylindrical escape- 

 ment (fig. 22) enables the constructor to dispense with the fusee. 



It will, of course, he understood, that in such arrangements, 

 while the wheel c is attached to the barrel, and by it to the 

 external extremity of ^he mainspring, the ratchet-wheel B is 

 attached to the axle T B (fig. 17), and by it to the internal 

 extremity of the mainspring. 



When a fusee is used, the ratchet-wheel being fixed upon its 

 axis, and not on that of the barrel containing the mainspring, 

 this method of obtaining a maintaining power is not applicable. 

 In such cases, the object is attained by two ratchet-wheels upon 

 the axle of the fusee, having their teeth and catches turned in 

 opposite directions, one of them being impelled by a provisional 

 spring, which only comes into play when the action of the main- 

 spring is suspended during the process of winding up. 



The fusee, with its appendages, as commonly constructed, 

 without a maintaining power, is drawn in fig. 29, the grooved 

 cone, with the ratchet-wheel attached to its base, being raised 

 Fi 29 from the cavity in the 



toothed wheel c D, in which 

 it is deposited, to show the 

 arrangement more clearly, 

 and in the edge of which 

 the catch n is placed, so 

 that it shall fall into the 

 teeth of the ratchet-wheel. 



When the watch is being 

 wound up, the chain passing 

 from the barrel to the 

 grooves of the fusee, the 

 teeth of the ratchet-wheel, 

 D A B, pass freely round the 

 cavity, the catch n falling 

 from tooth to tooth, and producing the clicking noise already 

 noticed. But when the watch is going, the tension of the chain 

 draws the fusee and the ratchet-wheel attached to it round in 

 the contrary direction, and, pressing the teeth of the ratchet-wheel 

 against the catch n, carries round the wheel c D, which gives 

 motion to all the other wheels, and through them to the hands. 

 Now, it will be evident, that when the watch is being wound up, 

 and the catch n relieved from the pressure of the teeth of the 

 ratchet-wheel, no motion will be imparted to c D, and consequently 

 the movement of the entire works will be suspended. 



The modification by which a maintaining power is obtained 

 by the combination of two contrary ratchet-wheels, is shown in 

 42 



