Because the _carbon_ of the wick comes into immediate contact with the _oxygen_ of the air. 257. _Why does holding a candle "upside down" put it out?_ Because the melted grease runs down too rapidly, and at too low a temperature to undergo combustion. It therefore _reduces the heat_, and extinguishes the flame. [Verse: "Lord, what is man that thou takest knowledge of him! or the son of man, that thou makest account of him."--PSALMS CXLIV.] 258. _Why is it more difficult to blow out the flame of a candle with a cotton wick than one with a rush wick?_ Because the cotton wick imbibes more of the combustible materials, and holds in its loose texture the inflammable gases in a state ready for combustion. 259. _Why does blowing sharply at a candle flame put it out?_ Because the breath drives away the vapour of the grease which, becoming gaseous, supports the flame. And because too rapid a flow of cold air reduces the temperature below the point at which combustion can be maintained. 260. _Why will a gentle puff of breath, if given speedily after the flame is extinguished, rekindle it?_ Because the _oxygen_ of the air combines with the _carbon_ and _hydrogen_ that are still escaping from the _heated wick_, and re-lights it. 261. _Why will not a similar puff rekindle the flame of a rushlight?_ Because its wick retains but _little heat_, and holds a comparatively small amount of combustible matter in a _volatile state_. 262. _Why is a fire, when it is very low, sometimes put out by blowing it?_ Because the too rapid flow of cold air _reduces the temperature_ of the burning mass. 263. _Why will a piece of paper twisted like an extinguisher put out a candle?_ Because, before the flame of the candle can ignite the paper, _the oxygen contained within it is consumed_, and the flame is suffocated. [Verse: "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 when the wick 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?_