CHRONOMETERS. 89 



length of time without being wound up: 1. By 

 increasing the number of teeth in the wheels; 

 2. By diminishing the number of teeth in the 

 pinions; 3. By increasing the length of the cord 

 that suspends the weight; 4. By increasing the 

 length of the pendulum; and 5. By adding to 

 the number of wheels and pinions. But, in pro- 

 portion as the time is augmented, if the weight 

 continues the same, the force which it communi- 

 cates to the last wheel G H, will be diminished. 

 It only remains to take notice of the number of 

 teeth in the wheels which turn the hour and minute- 

 hands. The wheel E performs one revolution in 

 an hour; the wheel N N, which is turned by the 

 axis of the wheel E, must likewise make one revo- 

 lution in the same time; and the minute-hand is 

 fixed to the socket of this wheel. The wheel N 

 has 30 teeth, and acts upon the wheel O, which has 

 likewise 30 teeth, and the same diameter; conse- 

 quently the wheel O takes one hour to a revolution: 

 now the wheel O carries the pinion p, which has 

 six teeth, and which acts upon the wheel q q, of 

 72 teeth ; consequently the pinion p makes twelve 

 revolutions while the wheel q q makes one; and, 

 of course, the wheel q q takes twelve hours to one 

 revolution, and upon the socket of this wheel the 

 hour-hand is fixed. 



All that has been said here concerning the revo- 

 lutions of the wheels, &c. of clocks, is equally 

 applicable to the general movements of watches. 



Thus it is plain — 1st, That the weight P turns 

 all the wheels, and at the same time continues the 

 motion of the pendulum; 2nd, That the quickness 

 of the motion and wheels is determined by that of 

 the pendulum; 3rd, That the wheels point out the 

 parts of time divided by the uniform motion of the 



