FUNDAMENTAL PRINCIPLES. 13 
terminal drop just asif the load were concentrated at its 
middle point. Hence, for all practical purposes, by making 
this assumption, equations (1), (4), (5) can be used in 
calculating the line. 
To keep the voltage approximately uniform over a 
linear system of distribution is comparatively easy. Inthe 
most favorable case, a number of uniform loads moving uni-- 
formly, the drop is half that met with in the most unfavor- 
able distortion of the load, 7. e., bunching at the end of the 
line. ‘This latter condition brings the worst possible load 
upon the station, barring short circuits. Although long 
stretches of uniform conductor often occur in railway prac- 
tice it is usual to reinforce the working conductor by feed- 
ers variously arranged, as will be shown later. Such feed- 
ers were very necessary in the early days when trolley wire 
as small as No. 4 was used, but now, when No. oo is very 
  
  
  
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A i : 
BIG: 7. 
commonly employed, elaborate feeding systems are less 
necessary for linear working. ‘The most important linear 
distributions are likely to come in long interurban roads, 
which often demand special methods of feeding. What- 
ever these may be, the uniform working conductor is of 
sufficient importance in every system to warrant this dis- 
cussion of its general properties. 
As a corollary to this general investigation, it is evi- 
dent that in dealing with any linear system such as A B, 
Fig. 6, the best point for the power station isat the middle 
point of the line, since under the conditions of uniform load 
supposed, this point would give the smallest average drop. 
Since I, in such case is one-half of its value when the whole 
line is fed from A, the total copper by equation (5) is re- 
duced to one-fourth the amount for the same loss. 
Considering now the branched type of distribution, 
shown in Fig. 2, it is best to take it up in the simplest 
available form. ‘This, Fig. 7, shows a main line, A B D,