8S CHRONOMETERS. 



which it occasions at every revolution, are con- 

 tained 1 20 times in 7200, the number of vibrations 

 performed by the pendulum in an hour. 



To determine the number of teeth for the wheels 

 E E, and their pinions e, f> it must be remarked, 

 that one revolution of the wheel E must turn the 

 pinion e as many times as the number of teeth in 

 the pinion is contained in the number of teeth in 

 the wheel. Thus, if the wheel E contains 72 teeth, 

 and the pinion e 6, the pinion will make twelve 

 revolutions in the time that the wheel makes one; 

 for each tooth of the wheel drives forward the 

 tooth of the pinion; and when the six teeth of the 

 pinion are moved, a complete revolution is per- 

 formed ; but the wheel E has, by that time, only 

 advanced six teeth, and has still 66 to advance, 

 before its revolution is completed, which occasions 

 eleven more revolutions of the pinion. For the 

 same reason, the wheel F having 60 teeth, and the 

 pinion f 6, the pinion will make ten revolutions 

 while the wheel performs one. Now, the wheel F, 

 being turned by the pinion e, makes twelve revo- 

 lutions for one of the wheel E ; and the pinion f 

 makes ten revolutions for one of the wheel F; con- 

 sequently the pinion f performs 10 times 12, or 

 120 revolutions, in the time the wheel E performs 

 one. But the wheel G, which is turned by the 

 pinion f t occasions 60 vibrations in the pendulum 

 each time it turns round; consequently the wheel 

 G occasions 60 times 120, or 7200 vibrations of 

 the pendulum, while the wheel E performs one 

 revolution ; but 7200 is the number of vibrations 

 made by the pendulum in an hour, and conse- 

 quently the wheel E performs but one revolution 

 in an hour, and so of the rest. From this reasoning, 

 it is easy to discover how a clock may go for any 



