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delicate adjustment of the two machines 

 is necessary. If such were to be the case, 

 it is obvious that the system would not 

 be suitable for use in central stations, 

 where the service must be carried on day 

 and night, and perferably, by a staff not 

 composed of skilled electricians. If a 

 battery of alternators be already running 

 in parallel, and it be desired to add 

 another machine, the obvious precaution 

 which an ordinary attendant would take 

 is to excite its field, and to run the 

 machine up to the proper speed before 

 joining it to the circuit. Some devices 

 have been introduced for indicating the 

 coincidence of phases by means of glow- 

 lamps, but as the use of these requires 

 careful attention and quickness of per- 

 ception on the part of the operator, it 

 would be preferable to so construct the 

 machines that absolute coincidence of 

 phase should not be required. If each 

 alternator is driven by its own engine 

 and if the latter is provided with a good 

 governor, there will be no difficulty in 

 obtaining very approximately the right 



