Motive power. To represent clearly the costs, etc., of the three
systems under this head, let us assume a road. Take, if you please, a
double line 6 miles long, and operating 24 cars with speed of 6 miles
an hour, and running 20 hours out of 24. This would call for 48 horses
on the track and 192 horses in the stables, or a total of 240 horses;
at $160, counting harness, etc., this would cost $38,400.

With electricity we will proceed as follows: The weight of car with 30
passengers and motor attachments would be about 9,000 lb. It is easily
calculated that to propel the same at the specified rate on a level
would take about 1.75 horse power, a total of 42 horse power. To make
allowances for grades we can calculate that, if the entire road was
one gradient of three per cent., each car would take about 6.4 horse
power, or since only 12 are going up, a total of 76.8 horse power. It
will be fair now to take the average of these two, or 59.4 horse power
for an average road. Allowing 35 per cent. loss from engine to work
done in actually propelling car, we would have to have 91.3 horse
power. Allowing a good safety factor, it would be well to put in a 150
horse power plant. This would cost complete $7,000; necessary dynamos,
$3,500. Among these figures should be counted cost of conductor of
sufficient size to allow of but three per cent. in energy to overcome
its resistance. This I have calculated using a potential of 600 volts;
and find that the total cost of six miles copper conductor is $16,000
with above conditions. The total cost is now seen to be $26,500.

As to cables, since the recovery of energy available for tractive
purposes is but 35 percent., then the engine of 169 horse power
represents what must be had. Allowing a generous factor of safety, let
us say that a 250 is all sufficient. This would cost complete and
erected about $12,000. The cable would cost $15.000, and gears, etc.,