638 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



In order that these electric regulators, whatever system is adopted, 

 should work with constancy and regularity, it is obvious that they 

 require constant attention and care. The proper state of the various 

 pieces, that of the regulating clock, and above all the maintenance of 

 the battery, are conditions of the first necessity. This is so evident 

 that we need not insist on it. But since, after all, one of these 

 conditions may fail, it is plain that the very thing which constitutes 

 the superiority of this arrangement over ordinary clocks, namely, the 



'Flo. 418. Breguet's illuminated clock 



working together of all the timepieces of the town or railway, would 

 be a great disadvantage in case of an interruption. It is advisable, 

 therefore, not only that the regulators should be independent, as we 

 have seen to be the case in Garnier's system, but the motion should 

 not depend on a single regulating clock. By dividing the town into 

 departments, each of which possesses a regulator, such a great incon- 

 venience as this is diminished in like proportion. 



