SPECIAI, METHODS OF DISTRIBUTION. 87 
properly applied for railway purposes it should become 
the equivalent of an enormous overcompounding applied, 
not to the whole system, but only to such parts of it as re- 
quire reinforcement. ‘Take the case of a simple interurban 
road (Fig. 50). Its office, let us suppose, is to connect 
cities C and D in addition to handling a considerable local 
trafficin D and a larger.one in C. The power station, 
at A, was originally devoted to the local work in Cand now 
has to be utilized to operate the whole system. The dis- 
tance from A to B, the center of distribution in D, is ten 
miles. Under what circumstances and how may the 
boosting system be profitably employed? Let the maxi- 
  
F1c. s50. 
mum sustained output in D be 500 amperes, including 
both local traffic and interurban cars. From what has 
already been said it is clear that if these 500 amperes were 
needed continuously the booster system would be simply a 
rat hole into which the management would pour about 
$8000 per year. On the other hand if the 500 amperes is 
a maximum load reached normally only a couple of hours 
a day, boosting could be profitably employed. No system 
is better fitted for furnishing additicnal power over moder- 
ate distances during brief periods of excessive load. Just 
how long boosting could be used to advantage would de- 
pend on the character of the variations in the load. The 
general rule regarding the economics of the matter is that 
a drop in the line great enough to necessitate boosting at 
average load is never justified, while if at an economical 
average drop the drop at maximum load is too great to be