THE WORKS OF A WATCH. 



381 



times in an hour — the common rate of a watch 

 that shows seconds. 



Having seen how the motions are regulated, we 

 may consider the rate of i evolution in the wheels, 

 according to the number of leaves in the pinions, 

 or of the teeth in the circumference of the wheels. 

 The central wheel, a, that w^hich is moved by the 

 fusee, has sixty-four teeth ; these fall into the pin- 

 ion of the third wheel, b, which has eight leaves, 

 the wheel itself having sixty teeth ; these sixty 

 teeth play into the pinion of the fourth wheel, c, 

 which has eight leaves. The central wheel going 

 round once in the hour, the fourth wheel will 

 go round sixty times in an hour, and with the 

 hand attached to its axle it will mark seconds. 



This will be more easily understood by a refer- 

 ence to the sketch. The wheel on the axis, a, to 

 which the minute-hand is attached, turns round 

 once in an hour. Its sixty-four teeth play upon 

 the pinion on the axle, b ; as this has eight leaves, 

 it will revolve once for every eight teeth of a, and 

 consequently eight times during the whole revolu- 

 tibn of A, that is, in an hour. The wheel on the 

 same axle, b, has sixty teeth, which turn the eight- 

 leafed pinion of c ; it will, therefore, turn the axle. 



