WATCH 



6212 



WATCH 



to protect the face; this stylo is called a hunt- 

 ing case, because such covers were once used 

 almost exclusively on watches carried to the 

 hunt. If the face is unprotected by such a 

 cover, the watch is called open-faced. 



The works, commonly called the movement, 

 consists of a train of wheels, the spring which 

 turns them, and the escapement which regu- 

 lates their speed. The train of wheels oper- 



TRAIN OF WHEELS IN A WATCH 



(a) Mainspring, connected with stem- winding 



apparatus. 



(b) Center wheel, always in center; connected 



with wheels which drive second, minute 

 and hour hands. 



(c) Balance wheel. 



(rf) Escape wheel, moving back and forth timing 

 movement of other wheels. 



ates on the same principle as the wheels of a 

 clock. The second hand is attached to a wheel 

 which revolves once a minute, the minute hand 

 once an hour, and the hour hand once in 

 twelve hours. These various wheels are con- 

 nected by pinions, as shown in the illustration; 

 the number of teeth on both pinion and wheel 

 are arranged to give the proper number of 

 revolutions. The largest of the wheels, known 

 as the barrel, contains the mainspring, whose 

 unwinding turns the barrel. The barrel is con- 

 nected with the stem-winding device. A little 

 click or tooth catches the teeth of the ratchet 

 on the barrel and prevents it from slipping. 

 At the other end of the train is the escape- 

 ment, consisting of the escape wheel, the pal- 

 let, the fork, roller and roller pin, balance 

 wheel and hairspring. This device controls the 

 movement of the whole train of wheels and 

 it therefore takes the place of the pendulum in 

 a clock. 



The escape wheel has fifteen hooks or teeth. 

 The pallet is an anchorlike piece, with two 

 horns so shaped that first one and then the 

 other grips a tooth of the escape wheel. These 

 horns allow only one tooth at a time to slip 

 by. The pallet is fastened to a fork, which in 

 turn is fastened to the balance wheel by means 

 of a small disk called the roller. The roller pin 

 alternately holds and releases the fork, thus 

 allowing the escape wheel to turn and setting 

 the entire train of wheels in motion. The bal- 

 ance wheel takes the place in watches that was 

 once taken by the balance and the pendulum in 

 clocks. It is made so that it balances per- 

 fectly, its weight being equally distributed 

 throughout its circumference. The tiny screws 

 on its rim are put in for this purpose and also 

 to give the weight necessary for 18,000 vibra- 

 tions an hour. The motion of the balance 

 wheel is controlled by a fine hairspring of steel, 

 which is fastened to the balance wheel. In 

 most modern watches the tension in the hair- 

 spring can be regulated by a small lever. The 

 entire movement of a watch is set between two 

 metal plates, usually of brass, in which the 

 wheels are fastened. 



Stop Watches. The mechanism of a stop 

 watch is like that of the ordinary watch, ex- 

 cept that pressure on a spring is required to set 

 the train of wheels in motion. In the simplest 

 form the wheel which carries the seconds hand 

 is released by a push on the stem of the watch. 

 A second pressure stops the wheel, and a third 



TRAIN OF WHEELS 



Assembled in a row, to show more clearly their 

 relation to one another. 



pressure drives it back until the hand points 

 to the zero. This last result is brought about 

 by a cam which flies around when touched by 

 the lever. All stop watches, no matter how 

 complex, are elaborations of this simple device. 

 Watch Manufacture. The making of watches 

 by hand seems to have originated in Germany 

 about the year 1500. In that country, in Swit- 

 zerland and in England, it received its highest 

 development during the next three centuries, 

 and Swiss watches especially have retained their 

 reputation for excellence up to the present 



