A Guide To The Scientific Knowledge Of Things Familiar Part 9

Q. _Which burns the quicker, a BLAZING fire, or a RED HOT one?_

A. A _blazing_ fire burns out the fuel quickest.

Q. _Why do BLAZING COALS BURN QUICKER than red hot ones?_

A. In red hot coals, only the _mere surface_ is in a state of combustion, because the carbon is _solid_; but in a _blazing_ fire, (where the gases are escaping), the _whole volume of the coal throughout_ is in a state of decomposition.

Q. _What is SMOKE?_

A. _Unconsumed_ parts of fuel (princ.i.p.ally carbon), separated from the solid ma.s.s, and carried up the chimney by the current of hot air.

Q. _Why is there MORE SMOKE when COALS are FRESH added, than when they are red hot?_

A. Carbon (being solid), requires a great degree of heat to make it unite with oxygen, (or, in other words, to bring it into a state of perfect combustion): when coals are fresh laid on, _more carbon is separated_ than can be _reduced to combustion_; and so it flies off in smoke.

Q. _Why is there so LITTLE SMOKE with a RED HOT FIRE?_

A. When a fire is red hot, the _entire surface_ of the coals is in a _state of combustion_; so a very little flies off unconsumed, as smoke.

Q. _Why are there DARK and BRIGHT SPOTS in a CLEAR cinder FIRE?_

A. Because the _intensity_ of the combustion is _greater in some parts_ of the fire, than it is in _others_.

Q. _Why is the intensity of the combustion so unequal?_

A. Because the air flies to the fire in various and unequal currents.

Q. _Why do we see all sorts of GROTESQUE FIGURES in hot COALS?_

A. Because the _intensity_ of combustion is so _unequal_, (owing to the gusty manner in which the air flies to the fuel; and the various shades of red, yellow, and white heat mingling with the black of the unburnt coal), produce strange and fanciful resemblances.

Q. _Why does PAPER BURN more readily than wood?_

A. Merely because it is of a _more fragile texture_; and, therefore, its component parts are more easily heated.

Q. _Why does WOOD BURN more readily than coal?_

A. Because it is not so _solid_; and, therefore, its elemental parts are more easily separated, and made hot.

Q. _When a FIRE is LIGHTED, why is PAPER laid at the BOTTOM, against the grate?_

A. Because paper (in consequence of its fragile texture), so very readily catches fire.

Q. _Why is WOOD laid on the top of the paper?_

A. Because wood, (being more _substantial_), _burns longer_ than paper; and, therefore, affords a _longer contact of flame_ to heat the coals.

Q. _Why would not paper do without wood?_

A. Because paper burns out so _rapidly_, that it would not afford sufficient _contact of flame_ to heat the coals to combustion.

Q. _Why would not WOOD do WITHOUT shavings, straw, or paper?_

A. Because wood is too _substantial_ to be heated into combustion, by the flame issuing from a mere _match_.

Q. _Why would not the paper do as well, if placed on the TOP of the coals?_

A. As every blaze _tends upwards_, if the paper were placed on the _top_ of the fire, its blaze would afford _no contact of flame_ to fuel lying _below_.

Q. _Why should COAL be placed ABOVE the wood?_

A. As every flame tends _upwards_, if the wood were _above the coal_, the _flame_ would not rise _through the coal_ to heat it.

Q. _Why is a FIRE KINDLED at the LOWEST BAR of a grate?_

A. As every flame tends _upwards_; when a flame is made at the _bottom_ of a fire, it _ascends through the fuel_ and heats it: whereas, if the fire were lighted from the _top_, the flame would _not come into contact_ with the fuel piled below.

Q. _Why does COAL make such EXCELLENT FUEL?_

A. Because it is so very _hard_ and _compact_, that it burns away very slowly.

Q. _Why will CINDERS become RED HOT, quicker than COALS?_

A. Because they are _more porous_ and _less solid_; and are, therefore, sooner reduced to a state of combustion.

Q. _Why will not IRON CINDERS burn?_

A. Iron cinders are _cinders saturated with oxygen_; they are unfit for fuel, because they can imbibe _no more oxygen_, being saturated already.