Q. _Why is not the END of a long wick BURNT OFF, as it hangs over the flames?_ A. Because the length of the wick so diminishes _the heat of the flame_, that it is not _hot_ enough to burn it off. Q. _Why do PALMER'S METALLIC WICKS never need SNUFFING?_ A. The wick is divided into two parts, each of which _bends outward_ to the outside of the flame; where the _end is intensely heated_, and _separated_ from the wick by the current of air up the candle. Q. _Why do common CANDLES require to be SNUFFED?_ A. Because the heat of the flame is _not sufficient to consume the wick_; and the _longer_ the wick grows, the _less heat_ the flame produces. Q. _Why do WAX CANDLES NEVER need SNUFFING?_ A. The wick of _wax_ candles is made _of very fine thread_, which the heat of the flame is sufficient to consume: but the wick of _tallow_ candles is made _of coarse cotton_, which is too substantial to be consumed by the heat of the flame, and must be cut off by _snuffers_. Q. _Why does a PIN, stuck in a RUSH-LIGHT, EXTINGUISH it?_ A. Because a _pin_ (being a good conductor), _carries away the heat of the flame from the wick_, and prevents the combustion of the tallow. Q. _What is the SMOKE of a CANDLE?_ A. Solid particles of carbon separated from the wick and tallow, but not consumed. Q. _Why are SOME particles consumed and not OTHERS?_ A. The _combustion of the carbon_ depends upon its _combining with the oxygen of the air_: but as the outer surface of the flame _prevents the access of air to the interior parts_, therefore much of the carbon of those parts passes off in smoke. Q. _Why do LAMPS SMOKE?_ A. Either because the _wick is cut unevenly_, or else because _it is turned up too high_. Q. _Why does a LAMP SMOKE when the WICK is cut UNEVENLY?_ A. 1st--Because the _points of the jagged edge_ (being very easily separated from the wick,) _load the flame with more carbon than it can consume_: and 2ndly--As the heat of the flame is _greatly diminished by these bits of wick_, it is unable to consume _even the usual quantity of smoke_. Q. _Why does a LAMP SMOKE when the WICK is turned up too HIGH?_ A. Because more carbon is separated from the wick _than can be consumed by the flame_. Q. _Why do not "Argand burners" smoke?_ A. Because a current of air passes through the _middle of the flame_; and therefore the carbon of the _interior_ is consumed, as well as that _in the outer coating of the flame_. Q. _Why does a LAMP-GLASS DIMINISH the SMOKE of a lamp?_ A. Because it both _concentrates and reflects the heat of the flame_; in consequence of which, the heat is so greatly increased, _that very little carbon escapes unconsumed_. CHAPTER VI. ANIMAL HEAT. Q. _What is the cause of ANIMAL HEAT?_ A. Animal heat is produced _by the combustion of hydrogen and carbon_ in the capillary veins. Q. _What are CAPILLARY VEINS?_