SPECIAI, METHODS OF DISTRIBUTION, 95 
the drop without raising the working voltage at the motors. 
The ordinary three-wire system involves complication in 
the general wiring and does not secure mnearly as much 
economy in copper as would be desirable; the system of 
Fig. 54, while giving Cons;iderable economy on the high 
voltage side requires a special arrangement of motors; and 
finally the self contained three-wire system, with several 
excellent properties, demands two trolleys. 
What is really wanted for long interurban lines is some 
way of raising the working pressure on the line, without 
wasting much energy or introducing troublesome complica- 
tions. . It must be clearly understood that as a matter of 
economy the higher the voltage the better, providing that 
voltage can be utilized. If there were no practical objec- 
tions to employing a 2000 volt trolley system it would cer- 
tainly be used in preference to juggling with a nominal 500 
volt system in the rather vain attempt to cheat Ohm’s law 
out of its due tribute of copper. By far the simplest way 
of dealing with the long distance lines now frequently 
found is to face the matter squarely and see what can be 
done in the line of a higher working pressure on the line 
and at the motors. It is all very well to work out the most 
economical methods for supplying 500 volt motors at long 
distances, but all such are wasteful in the extreme com- 
pared with systems working, so far as transmission is con- 
cerned, with 1000 volts or more. Boosters and the three- 
wire system merely make the best of a very bad matter. 
In the early days of electric railways even 3500 volts 
was considered rather too high a voltage for motors and 
dynamos adapted to the severe strains of railway work. 
A few years of experience have shown that with proper 
care 500 volt apparatus is entirely reliable and in very 
many railway systems the working pressure is, save at 
times of very heavy load, nearer 600 volts than 500. The 
saving in copper introduced by even a moderate increase in 
working pressure is very considerable, since, other things 
being equal, the weight of copper required is inversely as 
the square of the voltage. The following table gives the