132 SCIENCE IN SHORT CHAPTERS. 



and conversion. In heating tlie 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 con- 

 verting 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 consider- 

 able 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 trustworthy 

 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 practically available. This 

 small illuminating residuum may, and doubtless will, be in- 

 creased by the progress of practical improvement ; but, from 

 the necessary nature of the problem, the power available for 

 illumination at the end of the series must always be but a small 

 portion of that employed at the beginning. 



In burning the gas derived from coal we obtain its illuminat- 

 ing power directly, and if we burn it properly we obtain nearly 

 all. The coke residuum is also directly used as a source of 

 heat. The chief waste of the original energy in the gas-works 

 is represented by that portion of the coke that is burned under 

 the retorts, and in obtaining the relatively small amount of 

 steam-power demanded in the works. These are far more 

 than paid for by the value of the liquid hydrocarbons and the 

 ammonia salts, when they are properly utilized. 



In concluding my narrative I may add that after Mr. Starr's 

 death the % patentees offered to engage me on certain terms to 

 carry on his work. I declined this, simply because I had seen 

 enough to convince me of the impossibility of any success at 

 all corresponding to their anticipations. During the interven- 

 ing thirty years I have abstained from further meddling with 

 the electric light, because all that I had seen then, and had 

 heard of since, has convinced me that although as a scientific 

 achievement the electric light is a splendid success its practi- 

 cal application to all purposes where cost is a matter of serious 

 consideration is hopeless, and must of necessity continue to 

 be so. 



Whoever can afford to pay some shillings per hour for a 



