COMMON THINGS CLOCKS AND WATCHES. 



mutual adaptation of the intermediate wheels and pinions, to 

 impart as many revolutions as may be desired to the escapement- 

 wheel G. 



The wheels which govern the motion of the hands are those 

 which appear in the figure between the watch face and the frame 

 XT. The relative power of the mainspring aud balance-wheel 

 must be so regulated that the wheel D shall make one revolution 

 in an hour. The axis upon which this wheel is fixed passing 

 through the centre of the dial, carries the minute hand, which 

 therefore revolves with it, making one complete revolution on the 

 dial in an hour. 



Upon this axle of the minute hand is fixed a pinion k, which 

 drives the wheel /, on the axle of which is fixed the pinion m, 

 which drives a wheel p, through the centre of which the axle 

 of the minute hand passes without being fixed upon it. Upon the 

 axle of the minute hand a small tube is placed, within which 

 it can turn. Upon this tube the hour hand, as well as the 

 wheel p, is fixed. The pinion k, therefore, fixed upon the axis of 

 the minute hand, imparts motion to the hour hand by the inter- 

 vention of the wheel /, the pinion i, and the wheel p. Since the 

 hour hand must make one revolution while the minute hand makes 

 twelve, it is necessary that the relative numbers of the teeth of 

 these intermediate wheels shall be such as to produce that 

 relation between the motions of the hands. An unlimited variety 

 of combinations would accomplish this, one of the most usual 

 being the following : 



Pinion it 8 teeth. 



Wheel I 24 



Pinion m . . . . 8 ,, 

 Wheels 32 



By this arrangement^ will make eight revolutions, while m and 

 7 make thirty- two ; or, what is the same, p will make one revo- 

 lution, while m and I make four. In like manner, / will make 

 eight revolutions, while k, and therefore the minute hand, makes 

 twenty-four ; or, what is the same, I will make four revolutions, 

 while k and the minute hand make twelve. It follows, therefore, 

 that />, and therefore the hour hand, makes one revolution, while 

 k, and therefore the minute hand, makes twelve, which is the 

 necessary proportion. 



In this case there is no seconds hand : but, if there were, its 

 motion would be regulated in like manner by additional wheels 

 and pinions. 



36. The manner in which the moving power of a weight, and 

 the regulating power of a pendulum are applied in a clock to 

 SO 



