SCIENCE IN RELATION TO THE ARTS. 211 



temperature to which the particles of solid carbon in the flame are 

 raised, and Dr. Tyndall has shown that, of the radiant energy set up 

 in such a flame, only the -^ part is luminous ; the hot products of com- 

 bustion carry off at least four times as much energy as is radiated, so 

 that not more than one hundredth part of the heat evolved in combus- 

 tion is converted into light. This proportion could be improved, how- 

 ever, by increasing the temperature of combustion, which may be ef- 

 fected either by intensified air-currents or by regenerative action. Sup- 

 posing that the heat of the products of combustion could be commu- 

 nicated to metallic surfaces, and be transferred by conduction or other- 

 wise to the atmospheric air supporting combustion in the flame, we 

 should be able to increase the temperature accumulatively to any point 

 within the limit of dissociation ; this limit may be fixed at about 2,300 

 C, and can not be very much below that of the electric arc. At such 

 a temperature the proportion of luminous rays to the total heat pro- 

 duced in combustion would be more than doubled, and the brilliancy 

 of the light would at the same time be greatly increased. Thus im- 

 proved, gas-lighting may continue its rivalry with electric lighting 

 both as regards economy and brilliancy, and such rivalry must neces- 

 sarily result in great public advantage. 



In the domestic grate radiant energy of inferior intensity is re- 

 quired, and I for one do not agree with those who would like to see 

 the open fire-place of this country superseded by the Continental stove. 

 The advantages usually claimed for the open fire-place are, that it is 

 cheerful, " pokable," and conducive to ventilation ; but to these may 

 be added another of even greater importance, viz., that the radiant 

 heat which it emits passes through the transparent air without warm- 

 ing it, and imparts heat only to the solid walls, floor, and furniture of 

 the room, which are thus constituted the heating surfaces of the com- 

 paratively cool air of the apartments in contact with them. In the 

 case of stoves, the heated air of the room causes deposit of moisture 

 upon the walls in heating them, and gives rise to mildew and germs 

 injurious to health. It is, I think, owing to this circumstance that 

 upon entering an apartment one can immediately perceive whether or 

 not it is heated by an open fire-place ; nor is the unpleasant sensation 

 due to stove-heating completely removed by mechanical ventilation ; 

 there is, moreover, no good reason why an open fire-place should not be 

 made as economical and smokeless as a stove or hot-water apparatus. 



In the production of mechanical effect from heat, gaseous fuel also 

 presents most striking advantages, as will appear from the following 

 consideration. When we have to deal with the question of converting 

 mechanical into electrical effect, or vice versa, by means of the dynamo- 

 electrical machine, we have only to consider what are the equivalent 

 values of the two forms of energy, and what precautions are necessary 

 to avoid losses by the electrical resistance of conductors and by fric- 



