34 SCIENCE OF HOME AND COMMUNITY 



consisted of some -open receptacle like a shell, filled with oil, 

 in which was placed a wick of some fibrous material. These 

 lamps gave a very weak and flickering light and gave off 

 much smoke. It was a long time before a chimney was in- 

 vented. The first lamp with a chimney was made about 

 one hundred twenty-five years ago by a Swiss named 

 Argand. 



Various kinds of oils have been used. During the first half 

 of the nineteenth century whale oil was in common use in 

 this country. This was later replaced by kerosene, which 

 has been in use for only about fifty years. 



The plan of lighting a house by gas carried to different 

 rooms through pipes was first tried about one hundred 

 twenty years ago. A little less than a hundred years 

 ago gas was first used to light the streets of an American 

 city. 



Finally came the electric light. The arc lamp for street 

 lighting was first used about forty years ago. A little later, 

 for use indoors, appeared the incandescent lamp, which is so 

 widely used to-day. 



Burning of the candle. When the candle is first lighted 

 the heat melts the paraffin, this liquid is drawn up the wick 

 by capillarity, the heat then changes the liquid to gas, and 

 the gas burns with a flame. The elements in the gas unite 

 with the oxygen of the air, and gases are given off, chiefly 

 carbon dioxid and water vapor. An ordinary flame consists 

 of two parts, a bluish inner portion and a yellowish outer 

 portion. This inner part consists of the unburned gas formed 

 by heating the liquid. The outer part consists of the burning 

 gases. The light of the flame is due to small particles of 

 carbon which become intensely hot, and glow, thus giving 

 off light. The yellowish color is due to the presence of small 

 quantities of compounds of a metal called sodium, which is 

 present in minute quantities even on the dust particles of 

 the air. 



