ELECTRICAL ENERGY. 221 



2. In the case of the traction systems, when the economical area of 

 direct distribution is passed, boosters should be employed directly or 

 in connection with batteries, to a distance of 10 or 12 miles from a 

 station, and beyond this rotary transformers, whether with or without 

 batteries, should be used. 



3. In the case of direct current lighting systems, the energy should 

 be transmitted to storage batteries situated at centers of consumption 

 either directly or by means of a rotary transformer and distributed 

 from them. 



4. Where batteries are used it is best to place them at the end of 

 feeder wires to obtain the advantage of a constant load on the wire. 



5. The best system for the long-distance transmission of energy for 

 general purposes is the three-phase alternating system. 



6. Commercial transmissions are in successful operation for distances 

 of 35 miles, and for voltages as- high as 15,000 volts. 



Experience with these plants shows that the transmission to 50 miles 

 with a pressure of 20,000 volts is practicable; beyond these limits the 

 transmission would be more or less experimental. 



