294. _Why does paper ignite more readily than wood?_
Because its texture is less _dense_ than that of wood; its particles
are therefore more _readily heated_ and decomposed.
295. _But if articles of loose texture are bad conductors of heat, why
do they so easily ignite?_
The fact that they are _bad conductors_ assists their ignition. The
heat which would pass from particle to particle of the dense substance
of iron, and be _conducted away_, accumulates in the interspaces of
paper, and ignites it.
296. _Why does wood ignite less readily than paper?_
Because its substance is _denser_ than that of paper; it therefore
requires a higher degree of heat to inflame its substance.
297. _Why does wood, when ignited, burn longer than paper?_
Because, being a denser substance, it submits a _larger number of
particles_, within a given space, to the action of the heat, and the
formation of gases.
298. _Why do we, in lighting a fire, first lay in paper, then wood, and
lastly coals?_
Because the paper is more easily ignited than wood, and wood than
coals; therefore the _paper_ assists the ignition of the _wood_, and
the _wood_ assists the ignition of the _coals_.
[Verse: "It is a good thing to give thanks unto the Lord, and to
sing praises unto thy name, O Most High."--PSALM XCII.]
299. _Why will not wood ignite by the flame of a match?_
It will do so, unless there is a great disproportion between the size
of the wood and the flame of a match. A _thin_ piece of wood will
ignite, but a square block will not, because the heat of the flame is
insufficient to raise the temperature of a _large surface_ to the point
that will drive out its gases.
300. _Why do we place the paper under the wood, and the wood under the
coals?_
Because heat and flame, when surrounded by air, have a strong tendency
to spread themselves _upwards_.
301. _Would it be possible to light the coals by putting the paper and
the wood upon the top?_
It would be possible; but the loss of heat would be so great, that a
_much larger quantity_ of paper and wood would be required.
302. _Why does a poker laid across the top of a dull fire revive it?_
Because the poker _radiates_ the heat it receives from the fire
downward upon the fuel.
Because, also, it divides the ascending air, and thereby _creates
currents_.
The amount of good which the poker does to the fire is very slight
indeed. Generally, the housewife stirs the fire first, and blows
or brushes away the ashes that prevent the influx of air. She then
places the poker upon the top, and the popular mind supposes that
the poker "draws" the fire. The custom of placing a poker over
the fire is of very remote antiquity. It was once believed that
forming _a cross_, by placing the poker over the bars, protected
the fire from the hostility of malignant _witches_!
303. _Why should fire-places be fixed as low as possible in rooms?_
Because heat _ascends_, and when the fire-places are high the lower
parts of the room are _inadequately warmed_.
Also, as currents of air fly towards the fire, elevated fire-places
_cause drafts_ about the persons of the inmates to a much greater
extent than they would if they were lower down.
[Verse: "Unto thee, O God, do we give thanks: for that thy name is
near thy wondrous works declare."--PSALM LXXV.]
304. _Why, if a piece of paper be laid with its flat surface upon the
fire, will it "char," but not ignite?_
Because, as in the case of the proper candle-extinguisher, the
_carbonic acid gas_ accumulating beneath it prevents its igniting.
305. _Why, if you direct a current of air towards the paper, will it
burst into a blaze?_
Because the carbonic acid gas is displaced by a current of air
containing _oxygen_.
306. _Why does water extinguish fire?_
Because it _saturates the fuel_, and prevents the gases thereof from
combining with the oxygen of the air.
307. _As water contains oxygen, why does not the oxygen of the water
support the fire?_
Because the affinity between the _hydrogen_ and _oxygen_ of the water
is so strong that fire cannot separate them.
Water may be decomposed by _heat_, as will be hereafter explained.
But the heat of an ordinary fire is insufficient. There is,
however, some reason for believing that, in cases of very large
fires, such as the accidental burning of houses, &c., when the
supply of water thrown upon the fire is very deficient, the water
_does_ become _decomposed_, and add to the fury of the flames.
308. _Why does the blacksmith sprinkle water upon the coals of his
forge?_
The blacksmith uses _small coals_ because the small pieces thereof are
more easily ignited than large lumps would be, and they convey heat
better by completely surrounding the articles put into the fire. He
sprinkles water on the coal dust _to hold its particles together by
cohesion_, until the heat forms it into a cake. A strong blast of hot
hair drives the vapour of the water away, and leaves a porous mass to
the action of the fire.
309. _Why, when the blacksmith thrusts a heated iron into a tankard of
water, do we recognise a peculiar smell?_
Because the intense heat disengages a small volume of the gases of
which water is formed.
[Verse: "Oh the depth of the riches both of the wisdom and knowledge
of God! how unsearchable are his judgments, and his ways past finding
out."--ROM. XI.]
310. _Which gas do we (in this instance) recognise by the smell?_
The _hydrogen_ gas. Oxygen gas possesses no odour.
311. _What is Spontaneous Combustion?_
Spontaneous combustion is that which occurs in various bodies when they
become highly heated by _chemical changes_.
312. _Why is heat developed during chemical changes?_
Because, as all bodies contain _latent caloric_, the disturbance of the
atoms of which those bodies are composed, during the new combinations
that constitute _chemical changes_, frequently sets the caloric free,
and an _accumulation of caloric_ produces spontaneous combustion.
313. _Does a match ignite spontaneously when drawn over a rough
surface?_
No. Because in this case the combustion arises from heat _applied by
friction_.
314. _Does phosphorous ignite spontaneously when held in a warm hand?_
Phosphorous will ignite when held in a warm hand, but it does not then
produce spontaneous combustion, because it ignites through the agency
of _applied heat_.
315. _But if a piece of dry phosphorous be sprinkled with powdered
charcoal it will ignite, without the application of heat. Why is this?_
Because the _carbon_ (charcoal) absorbs _oxygen_ from the air, and
conveys it to the _phosphorous_. Here are _chemical changes_ which
develope heat, and produce _spontaneous combustion_.
316. _Why do hay-stacks sometimes take fire?_
Because the hay, having become damp, decays, and passes on to a state
of _fermentation_, in which _chemical changes occur_, during which
heat is evolved. Hay, taking fire under these circumstances, would
exhibit _spontaneous combustion_.
[Verse: "Who hath woe? who hath sorrow? who hath contentions? who
hath babbling? who hath words without cause? who hath redness of the
eyes? * * * They that tarry long at the wine."--PROV. XXIII.]
317. _What substances are liable to produce spontaneous combustion?_
All substances which contain sugar, starch, and other components
liable to _fermentation_. All bodies that evolve, under low degrees of
temperature, _inflammable gases_. And all organic bodies undergoing
decay.
Grain, cotton, hemp, flax, coals, oily and greasy substances.
318. _What is the Ignis Fatuus (sometimes called "Will-o'-the-Wisp",
"Corpse Candles," and "Jack-o'-Lantern")?_
It is a flame produced by spontaneous combustion, caused by the decay
of animal or vegetable bodies, which evolve _phosphoretted hydrogen_
gas, under circumstances attended by a low degree of heat, sufficient
to ignite the gases. It is mostly seen over marshy places, and
burial-grounds.
Many a "Ghost Story" has owed its origin to these singular but
harmless appearances. People, ignorant of the cause, have been
terrified at the effect. To the fancy of an affrighted mortal,
the simple flame of the _Ignis Fatuus_ has assumed the form of
a departed friend, and even found a supernatural voice. If,
excited by a momentary daring, the beholder moved towards the
light upon which he gazed, it fled from him. If he turned from
it and walked away, it followed him, step by step. The darkness
of a lonely road, or the sacred solitude of a burial-place, have
been sufficient accessories to authenticate the appearance of a
spirit. And yet how simple the phenomenon? Matters so volatile as
those which produce the _Ignis Fatuus_ would naturally be driven
back by the motion in the air caused by an advancing body; and, on
the other hand, a body moving from them would create a current in
which the _Ignis Fatuus_ would follow. Poisonous gases, escaping
from decaying bodies, pass into the air and take fire. They are
thereby converted into harmless compounds. Thus we see that the
"ghost" which terrifies the mind of the ignorant, becomes a
"guardian angel" to the educated.
319. _Has spontaneous combustion ever occurred in living bodies?_
It has occurred in numerous instances to persons habituated to the
excessive use of spirits.
320. _Why should spontaneous combustion occur in the case of the
drunkard?_
Because spirituous drinks contain a large proportion of ALCOHOL, one
of the constituents of which is _hydrogen_. The vital energies of
the drunkard, being destroyed by excess, chemical agencies obtain an
ascendancy, and it is supposed that the _hydrogen_ of the alcohol
combines with the _phosphorous_ of the body to form _phosphoretted
hydrogen_, which ignites spontaneously, and literally consumes the
living temple.
[Verse: "Drought and heat consume the snow waters; so doth the grave
those which have sinned."--JOB XXIV.]
Cases of spontaneous combustion are of rare occurrence. But they
are sufficiently well authenticated by high medical authority,
in many parts of the world, to present an awful warning to
the inveterate drunkard. The cases of which we have read the
particulars present details of the most appalling description. How
signally the Almighty displeasure at intemperance is expressed,
when the very drink which imparts the mad pleasure of intoxication
is made the _direct_ instrument by which the drunkard is destroyed!