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 THE 



SCIENTIF- 

 ICALLY 

 BUILT 



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Know "the Works" of the 

 Watch You Buy 



T 



The most dependable moderate price 

 watch in the world 



and up 



HE hairspring upon the balance wheel 

 of a watch is similar in function to the 

 effect of gravity upon a pendulum in 

 a clock. A pendulum swings so far to the left or right and is 

 stopped and swung back to the point of impulse by gravity. 

 A hairspring retards the balance wheel of a watch and re- 

 volves it back to the point of impulse, which impulse is 

 given by the escapement. 



Therefore, as the hairspring controls the speed and arc of 

 vibration of the balance, or its resultant, time, it is of the 

 utmost importance to the time-keeping quality of the move- 

 ment that the balance and hairspring be mated in perfect 

 ratio as to the weight of the balance and the proper rela- 

 tion of that weight to the center of gravity and the strength 

 of the spring. 



To determine this absolute ratio, John Logan, a famous Waltham ho- 

 rologist, invented a vibratory machine (illustrated above) which so accu- 

 rately mates the Waltham balance wheel and the hairspring, so perfectly 

 selects the right hairspring for the particular balance wheel, that when 

 finally assembled in the watch the watch is a natural time-keeper. This 

 is one reason why the Waltham watch is famous for its close and con- 

 stant time-rate. 



The foreign watch balance and hairspring are of varying construction. 

 They are made by hand — one at a time — therefore it is impossible even 

 for a skilled watchmaker to determine the ratio weight of the balance to 

 the strength of the hairspring. 



Its determination is by the uncertain rule of thumb method in trying va- 

 rious hairsprings until one is found which approximately performs its 

 function. 



This is yet another reason why the Waltham watch, due to standardized 

 exclusive machinery, standardized material, absolute measurements and 

 known ratios, is the watch you should insist upon buying — 

 And why the world's leading horologists came to Waltham for time. 



This story is continued in a beautiful booklet in which you will find a 



liberal watch education. Sent free upon request. Waltham Watch Company, 



Waltham, Mass. 



WALTHAM 



THE WORLD'S WATCH OVER TIME 



'Mention The Geographic — It identifies you' 



