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., $8,000, making a total of $35,000.

The ratio of the three systems stands:  Electricity, 1; cable, 1.09; horse, 1.45.

4th.  Construction of tramway.

Figures upon this point must necessarily be either averages or approximations.  The nature of the locality socially, naturally, and we grieve to say it, politically, has a strong influence upon its construction.  Estimating on single track only, a horse road would cost as an average $9,000 per mile.  With electricity we have several methods we can avail ourselves of:  Surface, costing about $10,000; overhead double conductor, $15.696; underground, $23,500.

With cable but one method, the underground, is possible.  This cost is variously estimated at from $30,000 to $110,000 per mile; however, the latter figure is excessive.  A fair average would be $35,000.

The ratio of constructions could be fairly placed as follows, putting electricity as 1, by taking the average of the three methods at $16,732:  Horse road, 0.53; cable, 2.09.