472 FRAGMENTS OF SCIENCE 



In this way the dark rays emitted by the incandescent 

 carbons are converted into light rays of all colors. Still, 

 so powerless are these invisible rays to excite vision that 

 the eye has been placed at a focus competent to raise 

 platinum foil to bright redness, without experiencing any 

 visual impression. Light for light, no doubt, the amount 

 of heat imparted by the incandescent carbons to the air is 

 far less than that imparted by gas flames. It is less, be- 

 cause of the smaller size of the carbons, and of the com- 

 parative smallness of the quantity of fuel consumed in a 

 given time. It is also less because the air cannot pene- 

 trate the carbons as it penetrates a flame. The tempera- 

 ture of the flame is lowered by the admixture of a gas 

 which constitutes four-fifths of our atmosphere, and which, 

 while it appropriates and diffuses the heat, does not aid 

 in the combustion; and this lowering of the temperature by 

 the inert atmospheric nitrogen renders necessary the com- 

 bustion of a greater amount of gas to produce the neces- 

 sary light. In fact, though the statement may appear 

 paradoxical, it is entirely because of its enormous actual 

 temperature that the electric light seems so cool. It is 

 this temperature that renders the proportion of luminous 

 to non-luminous heat greater in the electric light than in 

 our brightest flames. The electric light, moreover, re- 

 quires no air to sustain it. It glows in the most perfect 

 air vacuum. Its light and heat are therefore not pur- 

 chased at the expense of the vitalizing constituent of the 

 atmosphere. 



Two orders of minds have been implicated in the de- 

 velopment of this subject: first, the investigator and dis- 

 coverer, whose object is purely scientific, and who cares 

 little for practical ends; secondly, the practical mechani- 



