244. _Why will a piece of paper, held three or four inches over the
flame of a candle, become scorched?_
[Verse: "Neither do men light a candle, and put it under a bushel,
but on a candlestick; 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. _Why will a piece of paper held 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_.
[Illustration: Fig. 2.--DIAGRAM SHOWING THE COMBUSTION OF A CANDLE.]
246. _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 _oxygen_ 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. _Why does the upper part of the flame_ (B) _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, and 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_ escapes 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 blade of a knife, be held between
the eye and the flame of the candle, so as to shut off the light
of the more luminous part, the pale fringe around the flame will
be found distinctly perceptible. _Incandesence_ means _heated to
whiteness_.
[Verse: "How oft is the candle of the wicked put out? and how oft
cometh their destruction upon them?"--JOB XXI.]
250. _Why does the flame terminate in a point?_
Because cold air rushes towards the flame in every direction, and
is carried upward. At the point where the flame terminates the cold
currents have so _reduced the temperature_ that combustion can no
longer be sustained.
251. _Why, if you hold anything immediately over the flame, will the
flame lengthen?_
Because, by preventing the rapid escape of the heated air, you maintain
a temperature which _increases the combustion_ at the point of the
flame.
252. _Why should persons whose clothes take fire, throw themselves
down?_
Because flame spreads most rapidly in an _upward_ direction.
253. _Why should persons whose clothes are on fire roll slowly about
when they are down?_
Because they thereby _press out_ the fire.
254. _Why does pressing a flame or a spark put it out?_
Because it prevents the contact of the flame or spark with the _oxygen_
of the air.
Extinguishers put out the flame of candles in the same manner. A
person dies from "suffocation" through the absence of oxygen; and
it is literally practicable to _"suffocate" a fire_.
255. _Why does the wick turn black as it burns?_
Because it consists principally of _carbon_.
256. _Why, when the point of the wick turns out and meets the air, does
it exhibit a bright spark?_
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?_
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
unperceived, 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?_
No; there is no such thing as "loss" in the operations of nature. Every
particle of the candle, now invisible, exists either in the form of
_gas_, _vapour_, or _water_, with, perhaps, a few solid particles that
may be called _ashes_, but which are too minute to excite attention.
[Verse: "I know that whatsoever God doeth, it shall be for ever:
nothing can be put to it, nor anything taken from it; and God doeth it
that men should fear before him."--ECCLES. III.]
The economy of nature should teach us a very impressive
lesson--_nothing is suffered to be wasted_, not even the slightest
atom. As soon as any body has fulfilled its purpose in one state
of being, it is passed on to another. The candle, existing no
longer as a candle, is flying upon the wings of the air as
_carbonic acid gas_, and as _water_. These probably find their
way to the garden or the field, where the carbonic acid gas forms
the _food of the plant_, and the water affords it a refreshing
_drink_. And can it be supposed that the Almighty Being, who has
thus economised the existence of the _material_ creation, should
be less mindful of the immaterial _soul_ of man? There _is_ an
eternity before us, the certainty of which is evidenced even by
the laws of the material creation.