SPECIAIL, METHODS OF DISTRIBUTION. 89 
methods of alternating current transmission to cases like 
that of Fig. 5o. 
Better than any method of increasing the loss in the 
line are various methods of increasing the working voltage. 
These effect the same or greater economy in copper with 
less loss of energy and are in very many cases preferable 
to any boosting scheme. Some of them are simply ap- 
plicable without any changes in the arrangement of the 
motors, while others require special motors or special 
arrangements of them. 
The application of the Edison three-wire system is the 
most generally known of these. Its principles are by this 
time very familiar to the public, consisting virtually of 
  
  
F16. 5I. 
employing two working devices in series as regards the 
voltage of transmission, while each separate device, con- 
nected between one of the transmission wires and the 
neutral wire, receives only the voltage for which it is de- 
signed. ‘T'he application of this device to railway work is 
well shown in Fig. 51. 'The outside terminals of the two 
generators are connected to two trolley wires while the 
neutral is connected to the track system. Hence each 
motor works on about 500 volts, while the transmission of 
the total energy is at 1000 volts. 
In this case the neutral wire is the track, which ordi- 
narily, as we have seen, has a rather good conductivity so 
that the saving in copper is very material. If the loads on 
the two sides of the system were perfectly balanced so that 
there would be no steady flow through the mneutral wire,