224 WATER, HEAT, AIR, AND LIGHT IN THE HOUSE 



candles originally took place in the household, and in- 

 volved much painstaking work. A wick was dipped into 

 the melted fat, allowed to cool, and then dipped again, 

 until the desired thickness was obtained. 



In modern candle-making (Fig. 208) the wick is set in a 

 mould, and the melted fatty material or paraffin (cf. 

 121) is poured around it in the mould. In former times 

 "snuffers" were required to remove the charred wick 

 inside the flame; nowadays, snuffers are not needed. 

 The reason for this is that in the modern candle one of the 

 threads of the wick is pulled more tightly 

 than the others. As a result the tip of 

 the wick curves outward to the edge of 

 the flame (Fig. 42, 49), where the air 

 oxidizes it completely. 



Kerosene Lamps. The discovery of petroleum 

 in Pennsylvania in 1859 (cf. Fig. 98, 121) had 

 a decided effect upon the world's lighting and 

 heating problems; for it furnished gasoline, kero- 

 sene, paraffin, etc. Gasoline has too low a flash- 

 ing point (cf. 122) to permit its use with a wick, 

 in lamps. Kerosene cannot be burned with a 

 wick alone, as the true oils can (cf. 224), because 

 it smokes. To increase the air supply, and so to 

 prevent smoking, kerosene lamps have chimneys. 

 The heated air and gases carried upward by convection create a draft; 

 thus fresh portions of air are drawn into the burner below the flame. 



To increase the amount of kerosene that can burn in a given time, 

 and, therefore, to get a more intense light, men use central draft 

 burners. These have circular wicks (Fig. 209), and air is drawn to the 

 inside of the circular flame as well as to the outside of it. 



253. Gas for Lighting. Illuminating gas is formed 

 when soft coal is heated in closed retorts (cf. 124), and 



Fig. 209. 



Central Draft Burner. 

 Air gets at the wick 

 both inside and out- 

 side. 



