ARTIFICIAL LIGHT 



291 



D 



electric light, it has become the most convenient and 

 effective method of lighting. 



199. How Lamps Make Light. Before animal oils or 

 carbon oils can burn in a flame, they must be vaporized, 

 that is, changed into a gas. The flame on the wick of 

 a tallow candle melts the tallow. The liquid tallow is 

 drawn up the wick and evaporated. The 

 flame raises this vapor to the kindling point, 

 at which temperature the carbon and hy- 

 drogen unite with the oxygen. The small 

 carbon particles, as they unite with the 

 oxygen, become so hot that they are self- 

 luminous. These glowing particles of car- 

 bon in the flame of the candle are the 

 light-producing part of the flame. If the 

 flame is cooled slightly by blowing at it, a 

 black smoke will come from it. This smoke 

 is composed of unburned carbon. CANDLE FLAME 



The light of a carbon oil lamp is made A, combustible 



, . , , i i gases from the 



by the glowing white carbon particles dur- me ited candle, 

 their oxidation. The carbon oil is &> bluish flame. 



C, luminous 



ing 



vaporized as it gets to the top of the wick, flame. D, hottest 

 If the burner of a lamp is not clean, not mo^lnvSe^" 

 enough air can pass through the holes 

 below the flame and the vaporized oil cannot get suf- 

 ficient oxygen for complete oxidation; the result is that 

 the lamp smokes and poisonous gases come from it. If the 

 wick is turned too high, not enough oxygen can enter the 

 burner to oxidize the gas and smoking also results. A 

 good oil lamp, well cared for, will not produce any smoke 

 or bad odor, but will make a good light. 



Gas lamps with a broad, open flame make light in the 

 same way as the oil lamp, namely, by the glowing par- 



