68 



THE EEA8ON WHY. 



f Neither do meu light a candle, and put it under a bushel, but on a candle- 

 stick ; and it giveth light unto all that are in the house." MATT. v. 



Because the hot air and gas produced by the burning of the 

 candle ascends rapidly. 



245. Wliy will a piece of paper hel& about an inch below 

 the flame of a candle scarcely become warmed? 



Because the heat ascends ; and only a little of it falls upon the 

 paper, and that by radiation. 



240. Why does the lower part of 

 the flame of a candle (D) burn of a 

 blue colour ? 



Because the hydrogen of the tallow, 

 having a stronger affinity for the oxy- 

 gen of the air than carbon has, ignites 

 first. Pure hydrogen burns with a 

 bluish flame. 



247. Why does the middle of the 

 flame (c) look dark ? 



Because it is occupied with gaseous 

 vapours, derived from the tallow, which 

 have not yet ignited. 



248. Wliy does the upper part of 

 the flame (v) produce a bright 

 yellow light? 



Because it is in this part of the 

 flame that the hydrogen of the candle, 

 and the oxygen of the air, combine, 

 there is just sufficient carbon mixed 

 with the hydrogen to improve its illuminating power. 



249. Why is there a fringe of pale light (A) around the 

 upper part of the flame ? 



Because some of the carbon escnpes in a state of incandesence, 

 and as soon as it reaches the air it combines with oxygen, and so 

 forms carbonic acid gas. 



If any dark body, such as the bladi of a knife, be held between the ey and 



