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<h2>CHAPTER XV.</h2> 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? [Pg 77] 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. <hr class="bible-verse" /> "It is a good thing to give thanks unto the Lord, and to sing praises unto thy name, O Most High."—Psalm xcii. <hr class="bible-verse" /> 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. [Pg 78] 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. <hr class="bible-verse" /> "Unto thee, O God, do we give thanks: for that thy name is near thy wondrous works declare."—Psalm lxxv. <hr class="bible-verse" /> 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? [Pg 79] Because the intense heat disengages a small volume of the gases of which water is formed. <hr class="bible-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. <hr class="bible-verse" /> 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 [Pg 80] which heat is evolved. Hay, taking fire under these circumstances, would exhibit spontaneous combustion. <hr class="bible-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. <hr class="bible-verse" /> 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? [Pg 81] 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. <hr class="bible-verse" /> "Drought and heat consume the snow waters; so doth the grave those which have sinned."—Job xxiv. <hr class="bible-verse" /> 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! <hr class="chap" /> <div style="break-after:column;"></div>

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