FUNDAMENTAIL PRINCIPLES. TS 
to its own conditions. ‘T'aking now a drop for each line, 
according to the dictates of economy or convenience, and fig- 
uring the conductors from (10) with the respective currents, 
an area is found for the conductor belonging to each line. 
Then the cross section of copper required from A to the 
first branch is [¢#2]1 -+ [cm]m—+ . . . . ‘That from the 
first to the second branch is [¢ 72]m + [c m]n—+-- 
and so on. In practice the conductors would be 1nstalled 
of the nearest convenient size, neglecting small variations 
of K from the calculated amount at the termini of the 
various lines. 
The same procedure applies to all sorts of independent 
lines radiating and fed from a common center, whether or 
not these lines have any sections in common. 
We have thus far assumed all lines to be uniformly 
loaded all along their lengths. It often happens how- 
  
  
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ever that for some cause a line is loaded unequally. In 
the long run, grades partially compensate themselves, 
since as many cars run down by gravity as go up by the 
expenditure of extra power, so that their effect shows 
more in the variations of power required than in the total 
amount. Not infrequently, however, from the effect of 
grades, curves or local cars in an extended system, there 
is a regular demand for extra power at some point of the 
line, This is shown in Fig. 9. Here the line, A B, is 
divided into ten sections, each equally loaded, except 
that at 8 the load is three times the normal. Now it has 
just been shown that a uniformly distributed load is the 
same in effect as if it were concentrated at the middle 
point of the loaded line; that is, the electrical loads, like 
mechanical ones, act as if concentrated at their center of