LIGHT, COLOR, AND SOUND 115 



carbon heated by outside means, such as mantle gas-burners, 

 electric incandescent lamps, electric arc lamps, etc. 



A flame is caused by the glowing of solid particles that 

 have been volatized, converted into vapor, and rendered 

 luminous by intense heat. The flame of a common lamp 

 or candle is produced by the oil or melted tallow rising be- 

 tween the fibers of the wick through capillary attraction 

 (attraction which causes liquids to go up into minute open- 

 ings). When the wick is ignited, the oil* is heated to a state 

 of vapor, which inflames as the oil first raised is used in burn- 

 ing. Other portions are attracted up the fibers, become 

 vapor, and are burned likewise. In this way a constant, 

 and steady combustion is maintained. The flame of a lamp 

 is hollow, not solid, as the heated vapor must combine 

 with oxygen before combustion can ensue. Hence, only 

 the portions that come in contact with the air are trans- 

 formed into flame. The vapor that rises from the wick in 

 the center rises unburned. The hollow part of the flame 

 is indicated by the darker and less luminous portion seen 

 just above the wick. 



115. Standard of Light. The only standard of light 

 used in this country is the English standard candle. The 

 unit is one candle-power, which is the amount of light given 

 off by a spermaceti candle, weighing 1200 g. and burning 

 120 grains per hour. Photometry is that part of the science 

 of light that deals with the measurement of luminosity. 



116. Importance of Proper Lighting. The problem of 

 an adequate amount of light presents itself to every manu- 

 facturer and city-dweller. With the increasing value of 

 space and the constant crowding of buildings, the natural 



