DIRECT FEEDING SYSTEMS. 71 
load can be considered as concentrated at the middle point of 
each section. Determining the center of gravity of the three 
existing sections by Fig. 47, constructed like Fig. 10, we 
find thiscenter at e. Combining with this the effect of the 
proposed extension, it appears that the addition of this 
extra load would shift the center of gravity to ¢!, a dis- 
tance of somewhat less than soo ft. ‘T'ransferring these 
points to Fig. 46 we have the theoretical location for the 
power station. 
Its practical location is, however, a very different mat- 
ter. Very many things besides cost of copper for distribu- 
tion enter into the problem. In the first place ¢ may fall 
in a locality in which 
f real estate is very valu- 
able, so that it will pay 
to shift the center of 
distribution a consider- 
able distance rather than 
endure the cost of a site 
for the power station at 
e. Again e may be in- 
convenient with respect 
F1c. 47. to coal and water sup- 
ply. The cost of carting 
coal or pumping the water for condensation purposes may 
very easily outweigh the saving in copper due to distribu- 
ting from the theoretical point. It will perhaps be found 
that there is a considerable region within which the station 
can profitably be shifted to obtain cheap land, coal and 
water. It is not difficult to form an idea of the extent of 
this region. 'T'o do so, however, we need an approximate 
idea of the cost of copper for distributing the necessary 
power from the point e. This is very quickly obtained. 
We can consider a load of sixteen cars as concentrated at @ 
(Fig. 47). 'Thisis approximately 3500 ft. frome. Sim- 
ilarly six cars are at 4, 5000 ft., and four cars at ¢, 3o00ft. 
We have seen in studying Fig. 10 that the total weight of 
copper required for such a system is 
a=10