CONCLUSION. 295 



America are about to be illuminated by this system, of which 

 we believe we have not heard the last word. 



It is already certain that a more complete study of the 

 division of the light will lead to results more satisfactory 

 than those already known. 



In order that some idea may be formed of the improve- 

 ments within our reach, it will suffice for me to say that, in 

 the investigations hitherto made, the various elements that 

 play an important part in the magnitude of the effect pro- 

 duced have not been sufficiently attended to. Thus, for 

 example, a well-known relation between the resistance of the 

 external circuit and that of the generator can greatly increase 

 the proportion of the useful work. Nor should it be for- 

 gotten that the intensity of the light varies in proportion ever 

 so much greater than that of the intensity of the electric 

 current. It is already known that the calorific action pro- 

 duced by the current varies as the square of its intensity, 

 but the resulting light varies in a still higher ratio; for, accord- 

 ing to Preece, a platinum wire heated to 2,600 F. gives forty 

 times as much light as when it is heated to 1,900 F. This 

 explains why the division of the light is attended by so great 

 a loss ; since with each weakening of the current resulting 

 from this division, there is a loss of light which may, under 

 certain conditions, attain the eleventh power of the ratio of 

 the diminution of the current. 



All these considerations show that the solution of the 

 lighting problem requires much further investigation before 

 it becomes altogether practical ; but we believe that no one 

 of the questions belonging to it is insoluble, and that before 

 long we shall witness at least a partial transformation in 

 public illumination. 



