COMMON THINGS CLOCKS AND WATCHES. 



Balance-wheel. 34. Its vibrations uniform. 35. General explana- 

 tion of a watch. 36. Of a clock moved by a weight. 37. Method 

 of regulating the rate. 



22. IP the action of the anchor of the pendulum upon the 

 escapement- wheel be attentively considered, it will be perceived 

 that one tooth only of the escapement passes the anchor for each 

 double vibration made by the pendulum. Thus, if we suppose 

 that when the pendulum is at the extreme left of its range, the 

 right-hand pallet is between the teeth m' and n' t the tooth ' will 

 escape from the pallet c when the pendulum, swinging from left 

 to right, comes to the vertical position, which is the middle of its 

 swing. While it rises to the extreme right of its range, the tooth 

 n' advances to the place which m' previously occupied, and at the 

 same time the tooth m advances to the place which n previously 

 occupied ; but, at the same time, the pallet A, carried to the right, 

 enters between m and the succeeding tooth, and arrests the further 

 progress of the wheel. When the pendulum then swings to the 

 left, the wheel continues to be arrested until it arrives at the 

 middle of its swing, when the tooth below m escapes from the 

 pallet A, but at the same moment the pallet c enters below the 

 tooth which is above n', and receiving it at the end of the swing, 

 stops the motion of the wheel. Thus it appears,, that tooth after 

 tooth, in regular succession, falls upon the pallet c upon the arrival 

 of the pendulum at the extreme left of its play after each double 

 oscillation. 



If the pendulum be so constructed that it shall vibrate in a 

 second, and that it be desired that the escapement-wheel shall 

 make a complete revolution in a minute, that is during sixty 

 vibrations of the pendulum, the wheel must have thirty teeth. 

 In that case, one tooth passing the anchor during each double 

 oscillation from right to left, and back from left to right, thirty 

 teeth, that is the whole circumference of the wheel, will pass the 

 anchor in thirty double oscillations, or in sixty single swings of the 

 pendulum, the time of each swing being one second. 



23. The manner in which different rates of revolution can be 

 imparted to the different hands of a clock or watch, by tooth 

 and pinion work, is easily rendered intelligible. 



The wheels commonly used in watch and clockwork are formed 

 from thin sheets of metal, usually brass, which are cut into 

 circular plates of suitable magnitude, upon the edges of which 

 the teeth are formed. The edges of the wheels thus serrated are 

 brought together, the teeth of each being inserted between those 

 of the other, so that if one be made to revolve upon its axle, its 

 teeth pressing upon those of the other, will impart a motion of 

 revolution to the other. 

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