ELECTRIC LIGHTING. 83 



and solid hydrocarbons, I speak thus plainly and with full 

 confidence. 



There is yet another consideration, and one of vital im- 

 portance, to be taken into account, viz., that whether we 

 use the electric light derived from a dynamo-electric source, 

 or coal-gas our primary source of illuminating power is 

 coal, or rather the chemical energy derivable from the com- 

 bination of its hydrogen and carbon with oxygen. Now 

 this chemical energy is a limited quantity, and the progress 

 of Science can no more increase this quantity than it can 

 make a ton of coal weigh 21 cwts. by increasing the quan- 

 tity of its gravitating energy. 



The demonstrable limit of scientific possibilities is the 

 economical application of this limited store of energy, by 

 converting it into the demanded form of force without 

 waste. The more indirect and roundabout the method of 

 application, the greater must be the loss of power in the 

 course of its transfer and conversion. In heating the boiler 

 that sets the dynamo-electric machine to work, about one- 

 half the energy of the coal Is wasted, even with the best 

 constructed furnaces. This merely as regards the quantity 

 of water evaporated. In converting the heat-force into 

 mechanical power raising the piston, etc., of the steam- 

 engine this working half is again seriously reduced. In 

 further converting this residuum of mechanical power into 

 electrical energy, another and considerable loss is suffered 

 in originating and sustaining the motion of the dynamo- 

 electric machine, in the dissipation of the electric energy 

 that the armature cannot pick up, and in overcoming the 

 electrical resistances to its transfer. 



I am unable to state the amount of this loss in trust- 

 worthy figures, but should be very much surprised to learn 

 that, with the best arrangements now known, more than 

 one-tenth of the original energy of the coal is made practi- 

 cally available. This small illuminating residuum may, and 

 doubtless will, be increased by the progress of practical 

 improvement; but from the necessary nature of the prob- 

 lem, the power available for illumination at the end of the 

 series must always be but a small portion of that employed 

 at the beginning. 



