128 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
four miles, and the total amount of feeder copper relatively 
very small. In a less extreme case a closer calculation of 
feed copper would be required, and the matter could be 
examined with any necessary degree of precision. 
With two generating stations we may as a first ap- 
proximation assume that on the whole 400 k. w. is trans- 
mitted an average distance of 274 miles, say, 14,000 ft., 
and 100 k.w., a distance of, say, 40,000 ft. For the firstitem 
there would be mnecessary about sixty-six tons of copper 
and for the second about 134 tons, in all about 200 tons, 
costing, say, $36,000. 
Now if the power is transmitted from A to B we shall 
have a saving as before of $14,600 in the gross cost of gen- 
erating power, but lose about ten per cent in final efficiency 
since the net efficiency of line and apparatus will be 
roughly eighty per cent as against ninety per cent for the 
loss in feeders as above. For a 10,000 volt transmission 
about twenty tons of copper will be required costing, say, 
$5600. ‘The transformers and rotary converters with the 
requisite accessory apparatus may be lumped together at 
about $50 per kilowatt capacity. Allowing 400 k.w. capacity 
at the substation the cost of transmission line and appar- 
atus would be between $25,000 and $30,000. Assuming 
the latter and charging off ten per cent for interest and de- 
preciation we have a fixed charge of $3000 against the 
plant. Allowing four men at $75 a month each at the 
substation and five per cent extra on the plant for main- 
tenance of line and repairs we have a total charge against 
the transmission of $3000 - $3600 + $1500 4 10 per cent of 
the yearly energy which at 1.3 cts. per kilowatt hour would 
cost about $4745, in all about $12,845, showing a small 
saving in favor of the transmission of power. ‘The differ- 
ence, however, is so small that it could easily be thrown on 
the other side of the balance sheet by a slight change in 
local conditions, or on the other hand it might chance to be 
increased. The exact state of the case would have to be 
determined by a thorough examination of the change of 
cost of power with size of station in the localities in ques-