THE KEASON WHY. 71 



' When his candle shined upon my head, and when by his light I walked 

 through darkness." JOB xxix. 



264. Why do tallow candles require snuffing ? 



Because the oxygen of the air cannot reach the wick through the 

 body of flame therefore the unconsumed carbon accumulates upon 

 the wick. 



265. Why do composite and wax candles not require 

 snuffing ? 



Because their wicks are made by a series of plaits, by which they 

 are bent to meet the oxygen of the air, and consumed. 



266. Why does setting a glass upon a lamp increase its 

 brilliancy, though it shortens the -flame ? 



Because it conducts an increase of air to the flame, and the 

 greater supply of oxygen causes the escaping vapour of oil to be all 

 rapidly consumed. 



267. Why does a candle burn dimly ivhen the ivick has 

 become loaded with carbon ? 



Because the carbon radiates the heat, and disperses it, and 

 reduces the heat of the flame below that temperature which is 

 essential to its luminosity. 



268. What differences characterise the combustion of 

 carbon and of hydrogen ? 



The combustion of carbon takes place without the production of 

 flame. The charcoal (or carbon in any other form) being heated to 

 redness, enters directly into combination with the oxygen of the 

 surrounding air, and the carbonic acid gas, being invisible, passes 

 away unobserved. 



But in the combustion of hydrogen the heat developed is so 

 intense as to render the gas itself luminous, just as iron may be 

 heated to a red or white heat. 



269. What has become, of the candle when it has been burnt ? 

 It has been resolved partly into carbonic acid gas which, though 



unpcrceived, has diffused itself through the surrounding air ; and 

 partly into water, which escaped in the form of thin vapour. 



270. Has any part of the candle been consumed or lost ? 



