"God looked down from heaven upon the children of men, to see if there were any that did understand that did see God."—Psalm liii.
1.Why should we seek knowledge?
Because it assists us to comprehend thegoodness and power of God.
And it gives us power over the circumstances and associations by which we are surrounded: the proper exercise of this power will greatly promote our happiness.
2.Why does the possession of knowledge enable us to exercise power over surrounding circumstances?
Knowledge enables us to understand that, in order to live healthily, we require to breathe fresh and pure air. It also tells us that animal and vegetable substances, undergoing decay, poison the air, though we may not be able to see, or to smell, or otherwise discover the existence of such poison. Knowing this, we become careful to remove from our presence all such matters as would tend to corrupt the atmosphere. This is only one of the countless instances in which knowledge gives us power over surrounding circumstances.
3.Name some other instances in which knowledge gives us power.
Knowledge ofGeographyand ofNavigationenables the mariner to guide his ship across the trackless deep, and to reach the sought-for port, though he had never before been on its shores.
Knowledge ofChemistryenables us to separate or to combine the various substances found in nature. Thus we obtain useful andprecious metals from what at first appeared to be useless stones; transparent glass from pebbles, through which no light could pass; soap from oily substances; and gas from solid bodies.
"Give instruction to a wise man, and he will be yet wiser; teach a just man, and he will increase in learning."—Proverbs ix.
Knowledge ofMedicineenables the physician to overcome the ravages of disease, and to save suffering patients from sinking prematurely to the grave.
Knowledge ofAnatomyand ofSurgeryenables the surgeon to bind up dangerous fractures and wounds, and to remove, even from the internal parts of bodies, ulcers and diseased formations that would otherwise be fatal to life.
Knowledge ofMechanicsenables man to increase his power by the construction of machines. The steam-ship crossing the ocean in opposition to wind and tide, the railway locomotive travelling at 60 miles an hour, and the steam-hammer beating blocks of iron into useful shapes, are evidences of the power which man acquires through a knowledge of mechanics.
Knowledge ofElectricityenables man to stand in comparative safety amid the awful war of the elements. Lightning, the offspring of electricity, has a tendency to strike upon lofty objects by which it may be attracted. By its mighty powers churches or houses may be instantly levelled with the dust. But man, knowing that electricity is strongly attracted by particular substances, raises over lofty buildings rods of steel communicating with bars that descend into the ground. The lightning, rushing with indescribable force toward the steeple, is attracted by the bar of steel, and conducted harmlessly to the earth. Man may thus be said to take even lightning by the hand, and to divert its destroying force by the aid of Knowledge. And in countless other instances "Knowledge is Power."
4.Why do we breathe air?
Because the air containsoxygen, which is necessary to life.
5.Why is oxygen necessary to life?
Because it combines with thecarbonof the blood, and formscarbonic acid gas.
"Be not as the horse, or as the mule, which have no understanding: whose mouth must be held with the bit and bridle."—Psalm xxxii.
6.Why is this combination necessary?
Because we are so created that the substances of our bodies are constantly undergoing change, and this resolving of solid matter into a gaseous form, is the plan appointed by our Creator to remove the matter calledcarbonfrom our systems.
7.Why do our bodies feel warm?
Because, in the union ofoxygenandcarbon, heat is developed.
8.What is this union of oxygen and carbon called?
It is calledcombustion, which, in chemistry, means the decomposition of substances, and the formation of new combinations, accompanied by heat; and sometimes by light, as well as heat.
9.What is formed by the union of oxygen and carbon?
Carbonic acid gas.
10.What becomes of this carbonic acid gas?
It is sent out of our bodies by the compressure of the lungs, and mingles with the air that surrounds us.
11.Is this carbonic acid gas heavier or lighter than the air?
Pure carbonic acid gas is the heaviest of all the gases. That which is sent out of the lungs is not pure, because the whole of the air taken into the lungs at the previous inspiration has not been deprived of itsoxygen, and the nitrogen is returned. Therefore the breath sent out of the lungs may be said to consist ofair, with a large proportion ofcarbonic acid gas.
12.What is the composition of air in its natural state?
It consists ofoxygen,nitrogen, andcarbonic acid gas, in the proportions of oxygen 20 volumes, nitrogen 79 volumes, and carbonic acid gas 1 volume. It also contains a slight trace of watery vapour.
13.What is the state of the air after it has once been breathed?
It has parted with about one-sixth of its oxygen, and taken up an equivalent of carbonic acid. And were the same air to be breathedsix times successively, it would have parted withallits oxygen, and could no longer sustain life.
"A prudent man forseeth the evil, and hideth himself; but the simple pass on, and are punished."—Proverbs xxvii.
14.Is the impure air sent out of the lungs lighter or heavier than common air?
At first, being rarefied by warmth, it islighter. But, if undisturbed, it would becomeheavieras it cooled, and would descend.
15.Why is it proper to have beds raised about two feet from the ground?
Because at night, the bed-room being closed, the breath of the sleeper impregnates the air of the room with carbonic acid gas, which, descending, lies in its greatest density near to the floor.
16.What are the chief sources of carbonic acid gas?
The vegetable kingdom (as will be hereafter explained), the combustion of substances composed chiefly of carbon, the breathing of animals, and the decomposition of carbonic compounds.
17.Is breathing a kind of combustion?
It is. In the breathing of animals, the burning of coals, or of wood, or candles, &c., similar changes occur. Theoxygenof the air combines with thecarbonof the substance said to be burnt, and formscarbonic acid gas, which unfits the air for the purposes of either breathing or of burning, until it has been renewed by admixture with the air.
18.What is carbon?
It is one of the elementary bodies, and is very abundant throughout nature. It abounds mostly in vegetable substances, but is also contained in animal bodies, and in minerals. The form in which it is most familiar to us is that ofcharcoal, which is carbon almost pure.
19.What is meant by an elementary body?
An elementary body is one of those substances in which chemistry is unable to discover more than one constituent. For instance, the chemist finds that water is composed ofoxygenandhydrogen. Water is therefore acompoundbody. Butcarbonconsists ofcarbon only, and therefore it is called a simple, or elementary body.
"Where no wood is, there the fire goeth out: so where there is no tale-bearer, the strife ceaseth."—Proverbs xxvi.
20.Why is it dangerous to burn charcoal in rooms?
Because, being composed ofcarbonthat is nearly pure, its combustion gives off a large amount ofcarbonic acid gas.
21.What is the effect of carbonic acid gas upon the human system?
It induces drowsiness and stupor, which, if not relieved by ventilation, would speedily cause death.
22.What is the reason that people feel drowsy in crowded rooms?
Because the large amount of carbonic acid gas given off with the breaths of the people, makes the air poisonous and oppressive.
23.What other causes of drowsiness are there?
The candles, gas, or fires that may be burning in the rooms where people are assembled. Three candles produce as much carbonic acid gas as one human being; and it is probable that one gas-light produces as much carbonic acid gas as two persons.
24.Have people ever been poisoned by their own breaths?
In the reign of George the Second, the Rajah of Bengal took some English prisoners in Calcutta, and put 146 of them into a place which was called the "Black Hole." This place was only 18 feet square by 16 feet high, and ventilation was provided for only by two small grated windows.One hundred and twenty-three of the prisoners died in the night, and most of the survivors were afterwards carried off by putrid fevers. Many other instances have occurred, but this one is the most remarkable.
25.What is oxygen?
Oxygen is one of the most widely diffused of the elementary substances. It is a gaseous body.
"Stand in awe and sin not: commune with your own heart upon your bed and be still"—Psalm iv.
26.Why do persons who are walking, or riding upon horseback feel warmer than when they are sitting still?
Because as they breathe more rapidly, the combustion of thecarbonin the blood is increased by theoxygeninhaled, and greater heat is developed.
27.Why does the fire burn more brightly when blown by a bellows?
Because it receives, with every current of air, a fresh supply ofoxygen, which unites with thecarbonandhydrogenof the coals, causing more rapid combustion and increased heat.
28.Why does not the oxygen of the air sometimes take fire?
Because oxygen,by itself, is incombustible. The wick of a candle, which retains the slightest spark, being immersed in oxygen, will instantly burst into a brilliant flame; and even a piece of iron wire made red-hot, and dipped in oxygen, will burn rapidly and brilliantly. Oxygen, though non-combustible of itself, is the most powerfulsupporter of combustion.
29.Why do we know that oxygen will not burn of itself?
Because when we immerse a burning substance into a jar of oxygen, it immediately burns with intense brilliancy; but directly it is withdrawn from the oxygen, the intensity of the flame diminishes, and the oxygen which remains isunaffected.
30.Why do we know that oxygen is necessary to our existence?
Because animals placed in any kind of gas, or in any combination of gases, where oxygendoes not exist, die in a very short time.
31.Where is oxygen found?
It is found in the air, mixed withnitrogen; in water combined withhydrogen; in the tissues of vegetables and animals; in our blood; and in various compounds called, from the presence of oxygen,oxides.
32.Why is the oxygen of the air mixed so largely with nitrogen?
Becauseoxygenin any greater proportion than that in which it is found in the atmosphere, would be too exciting to the animalsystem. Animals placed inpure oxygendie in great agony from fever and excitement, amounting to madness.
"As vinegar is to the teeth, and as smoke to the eyes, so is the sluggard to him that sent him."—Proverbs x.
33.What is nitrogen?
Nitrogen is an elementary body in the form of gas.
34.Where is nitrogen found?
It is chiefly found in the air, of which it constitutes 79 out of 100 volumes. It may be mixed with oxygen in various proportions; but in the atmosphere it is uniformly diffused. It is found in most animal matter,except fat and bone. It is not a constituent of thevegetable acids, but it is found in most of thevegetable alkalies.
35.What are acids?
Acids are a numerous class of chemical bodies. They are generally sour. Usually (though there are exceptions) they have a great affinity for water, and are easily soluble therein; they unite readily with mostalkalies, and with the variousoxides. All acids are compounds of two or more substances. Acids are found in all the kingdoms of nature.
36.What are alkalies?
Alkalies are a numerous class of substances that have a great affinity for, and readily combine with,acids, formingsalts. They exercise peculiar influence upon vegetable colours, turning blues green, and yellows reddish brown. But they will restore the colours of vegetable blues which have been reddened byacids; and, on the other hand, theacidsrestore vegetable colours that have been altered by thealkalies. Alkalies are found in all the kingdoms of nature.
37.Could animals live in nitrogen?
No; they would immediately die. But a mixture ofoxygenandnitrogen, in equal volumes, constitutesnitrous oxide, which gives a pleasurable excitement to those who inhale it, causing them to be merry, almost to insanity; it has, therefore, been calledlaughing gas.
38.Why does nitrous oxide produce this effect?
Because it introduces into the body moreoxygenthan can be consumed. It, therefore, deranges the nervous system, and beinga powerful stimulant, gives an unnatural activity to the nervous centres and the brain.
"Lord, make me know mine end, and the measure of my days, that I may know how frail I am."—Psalm xxxix.
39.In what proportions are the atmospheric gases found in the blood?
The mean quantity of the gases contained in the human blood has been found to be equal to 1-10th of its whole volume. Invenousblood, the average quantity ofcarbonic acidis about 1-18th, that ofoxygenabout 1-85th, and that ofnitrogenabout 1-100th of the volume of the blood. Inarterialblood their quantities have been found to becarbonic acidabout 1-14th,oxygenabout 1-38th, andnitrogenabout 1-72nd.
40.Then is nitrogen taken into the blood from the air?
Such a supposition is highly improbable. It is probably derived fromnitrogenised food, just ascarbonic acidis derived fromcarbonised food.
41.What is venous blood?
Venous blood is that which is returning through theveinsof the body from the organs to which it has been circulated.
42.What is arterial blood?
Arterial blood is that which is flowing from the heart through thearteriesto nourish the parts where those arteries are distributed.
43.What is the difference between venous and arterial blood?
Venous blood containsmorecarbonic acid, andlessoxygen and nitrogen than arterial blood.
44.Will nitrogen burn?
It will not burn, nor will it support combustion.
45.What is the difference between "burning" and "supporting combustion?"
Oxygen gas will not burn of itself, but it aids the decomposition by fire of bodies that are combustible. It is therefore called asupporter of combustion. But hydrogen gas,though it burns of itselfwill extinguish a flame immersed in it. It is therefore said to be a body which willburn, butwill not support combustion.
"As coals are to burning coals, and wood to fire; so is a contentious man to kindle strife."—Proverbs xxvi.
46.What becomes of the nitrogen that is inhaled with the air?
It is thrown off with the breath, mixed withcarbonic acid gas, and flies away to be renewed by a fresh supply of oxygen.
47.Where does nitrogen find a fresh supply of oxygen?
In the atmosphere. Nitrogen is said to possess a remarkable tendency tomixwith oxygen, without having a positive chemicalaffinityfor it. That is to say, neither theoxygennor thenitrogenundergoes any change by the union, except that ofadmixture. The oxygen and the nitrogen still possess their own peculiar properties. Oxygen and nitrogen are found in nearly the same proportions in all climates, and at all altitudes.
48.In combustion does any other result take place besides the union of oxygen and carbon forming carbonic acid gas?
Yes. Usuallyhydrogenis present, which in burning unites withoxygen, and formswater.
49.What is hydrogen?
Hydrogen is an elementary gas, and is the lightest of all known bodies.
50.Will hydrogen support animal life?
It will not. It proves speedily fatal to animals.
51.Will hydrogen support combustion?
Although it will burn, yielding a feeble bluish light, it will, if pure, extinguish a flame that may be immersed in it. Hydrogen will thereforeburn, but will notsupport combustion.
52.Why will hydrogen explode, if it will not support combustion?
When hydrogen explodes it is always in combination withoxygen,or with the common air, which containsoxygen.Twomeasures of hydrogen andoneof oxygen form a most explosive compound.
"As smoke is driven away, so drive them away: as wax melteth before the fire, so let the wicked perish at the presence of God."—Psalm xlvi.
53.Why does hydrogen explode, when mixed with oxygen, upon being brought in contact with fire?
Because of its strong affinity foroxygen, with which, upon the application of heat, it unites to form water.
54.Where does hydrogen chiefly exist?
In the form ofwater, where it exists in combination withoxygen.Elevenparts of hydrogen, andeighty-nineof oxygen, form water.
55.Is hydrogen found elsewhere?
It is never found but in a state of combination; united with oxygen, it exists inwater; with nitrogen, inammonia; with chlorine, inhydro-chloric acid; with fluorine, inhydro-fluoric acid; and in numerous other combinations.
56.Is the gas used to illuminate our streets, hydrogen gas?
It is; but it is combined with carbon, derived from the coals from which it is made. It is therefore calledcarburetted hydrogen, which meanshydrogenwithcarbon.
57.How is hydrogen gas obtained from coals?
It is driven out of the coals by heat, in closed vessels, which prevent its union withoxygen.
58.What becomes of the water which is formed by the burning of hydrogen in oxygen?
It passes into the air in the form of watery vapour. Frequently it condenses, and may be seen upon the walls and windows of rooms where many lights or fires are burning. Sometimes, also, portions of it become condensed in the globes of the glasses that are suspended over the jets of gas.A large volume of these gases forms only a very small volume of water.
59.What becomes of the carbonic acid gas which is produced by combustion?
It is diffused in the air, which should be removed by adequate ventilation.
"I will both lay me down in peace and sleep: for thou, Lord, only, makest me dwell in safety."—Psalm iv.
60.What proportion of carbonic acid gas is dangerous to life?
Any proportion over the natural one of 1 per cent. may be regarded asinjurious. But toxicologists state thatfive per cent.of carbonic acid gas in the atmosphere isdangerousto life.
61.What are toxicologists?
Persons who study the nature and effects of poisons and their antidotes.
62.Which kind of combustible used for lighting tends most to vitiate the air?
Assuming all the lights to be of the same intensity, the degree in which the substances burnt would vitiate the atmosphere may be gathered from the number of minutes each would take to exhaust a given quantity of air. This has been found to be: rape oil, 71 minutes; olive oil, 72; Russian tallow, 75; town tallow, 76; sperm oil, 76; stearic acid, 77; wax candles, 79; spermaceti candles, 83; common coal gas, 98; canal coal gas, 152. Thus it is shown that rape oil ismost destructiveof the atmosphere, and that coal gas is theleast destructive.
63.Is an escape of hydrogen gas from a gas-pipe dangerous to life?
It is dangerous, first, byinhalation. There are no less than six deaths upon record of persons who were killed by sleeping in rooms near to which there was a leakage of gas.
It is dangerous, secondly, byexplosion.
In 1848, an explosion of gas occurred in Albany-street, Regent's-park, London. The gas accumulated in a shop for a very short time only. It had been escaping from a crack in the meter for about one hour and twenty minutes. The area of the room was about 1,620 cubic feet. When the gas exploded, it blew out the entire front of the premises, carried two persons through a window into an adjoining yard, and forced another person on to the pavement on the opposite side of the street, where she was killed. The effect of the explosion was felt for more than a quarter of a mile on each side of the house, and most of the windows in the neighbourhood were shattered. The iron railings over the area of the house directly opposite were snapped asunder; and a part of the roof, and the back windows of another house, were carried to a distance of from 200 to 300 yards. The pavement was torn up for a considerablelength, and the damage done to 103 houses was afterwards reported to amount to £20,000. Other serious explosions have taken place. The explosions of "coal damp," which frequently occur in mines, are of a similar character.
"O Lord, our Lord, how excellent is thy name in all the earth! who hast set thy glory above the heavens."—Psalm viii.
64.What proportion of hydrogen gas with atmospheric air will explode?
According to the researches of Sir Humphrey Davy,sevenoreightparts ofair, tooneofgas, produce the greatest explosive effect; whilelargerproportions of gas are less dangerous. A mixture ofequal partsof gas and air will burn, but it will not explode. The same is the case with a mixture oftwoofair, orthreeofair, andoneofgas; butfourofairandoneofgasbegin to be explosive, and the explosive tendency increases up tosevenoreightofairandoneofgas, after which the increased proportion of gas diminishes the force of the explosion.
65.What is the best method of preventing the explosion of gas?
Observe the rule,never to approach a supposed leakage with a light. Fortunately the gas, which threatens our lives, warns us of the danger by its pungent smell. The first thing to be done is to open windows and doors, and to ventilate the apartment. Then turn the gas off at the main, and wait a short time until the accumulated gas has been dispersed.
66.Does hydrogen gas rise or fall when it escapes?
Beingtwelve times lighter than common airitrises, and therefore it would be better for ventilation to open the window at thetopthan at thebottom. But all gases exhibit a strong tendency todiffuse themselves, and therefore they do not rise or fall in the degree that might be anticipated.
67.What proportion of hydrogen in the air is dangerous to life, if inhaled?
One-fiftieth part has been found to have aserious effectupon animals. The effects it produces upon the human system are those of depression, headache, sickness, and general prostration of the vital powers. It is therefore advisable to observe precautions in the use of gas.
"From the place of his habitation he looketh upon all the inhabitants of the earth."—Psalm xxxiii.
68.What proportion of gas in the air may be recognised by the smell?
By persons of acute powers of smelling it may be recognised when there isonepart ofgasinfive hundred parts of atmospheric air; but it becomes very perceptible when it formsonepart ina hundred and fifty. Warning is, therefore, given to us long before the point of danger arrives.
69.What other sources of hydrogen are there in our dwellings?
It arises from the decomposition of animal and vegetable substances, containingsulphurandhydrogen. These give off a gas calledsulphuretted hydrogen, from which the fætid effluviam of drains and water-closets chiefly arise. We should, therefore, take every precaution to secure effective drainage, and to keep drain-traps in proper order.
70.May the use of gas for purposes of illumination be considered highly dangerous?
Not if it is intelligently managed. The appliances for the regulation of gas are so very simple and perfect, that accidents seldom arise except from neglect. In England 6,000,000 tons of coal are usually consumed in the manufacture of gas, producing 60,000,000,000 cubic feet of gas. And yet accidents are of very uncommon occurrence.
71.What is heat?
Heat is a principle in nature which, like light and electricity, is best understood by itseffects. We popularly call that heat, which raises the temperature of bodies submitted to its influence.
72.What is caloric?
Caloric is another term for heat. It is advisable, however, to use the termcaloricwhen speaking of thecauseof heat, and ofheatas theeffectof the presence ofcaloric.
"While the earth remaineth, seed-time and harvest, and cold and heat, and summer and winter, and day and night, shall not cease."—Gen. viii.
73.What is the source of caloric?
The sun is its chief source. But caloric, in some degree, existsin every known substance.
74.What are the effects of caloric?
Heat which, in proportion to its intensity, acts variously upon all bodies, causingexpansion,fusion,evaporation,decomposition,&c.
75.Why is caloric called a repulsive agent?
Because its chief effects are toexpand,fuse,evaporate, ordecomposethe substances upon which it acts.
76.What is an attractive agent, in contradistinction to a repulsive agent?
Chemical attraction, or affinity, is an attractive agent—as when bodies seek of their own natures to unite and form some new body.
77.When is a body said to be hot?
When it holds so muchcaloricthat it diffuses heat to surrounding objects.
78.When is a body said to be cold?
When it holds lesscaloricthan surrounding objects, and absorbs heat from them.
79.How may caloric be excited to develop heat?
By any means which cause agitation, or produce an active change in the condition of bodies. Thus friction, percussion, sudden condensation or expansion, chemical combination, and electrical discharges, all developeheat.
80.Why do "burning glasses" appear to set fire to combustible substances?
Because they gather into one point, orfocus, several rays ofcaloricas they are travelling from the sun, and the accumulation of caloric developes that intensity ofheatwhich constitutesfire.
81.What is a focus?
In optics, it is the point or centre at which, or around which, divergent rays are brought into the closest possible union.
"Yet man is born to trouble, as the sparks fly upward.—I would seek unto God, and unto God would I commit my cause."—Job v.
82.What is fire?
It is a violent chemical action attending the combustion of the ingredients offuelwith theoxygenof the air.
83.What are the properties of fire?
It imparts heat, which has the effect of expanding both fluids and solids.
It cannot exist without the presence of combustible materials.
It has a tendency to diffuse itself in every direction.
It cannot exist without oxygen or atmospheric air.
84.What elements take part in the maintenance of a fire?
Hydrogen, carbon, and oxygen. Hydrogen and carbon exist in thefuel, and oxygen is supplied by theair.
85.How does the combustion of a fire begin?
A match made of phosphorous and sulphur (highly inflammable substances) is drawn over a piece of sand-paper; thefrictionof the match induces the presence ofcaloric, which developesheat, and ignites the match, the burning of which is sustained by theoxygenof the air. The flame is then applied to paper or wood, and the heat of the flame is sufficient to drive outhydrogen gas, which unites with theoxygenof the air, and burns, imparting greater heat to thecarbonof the coals, which assumes the form of carbonic acid gas by union withoxygen, and in a little while all the conditions ofcombustionare established.
86.What are the properties of heat?
It may exist withoutfireorlight.
It is not sensible tovision.
It makes an impression upon ourfeelings.
It acts powerfully uponall bodies.
It has noweight.
It attends, or is connected with,all the operations of nature.
It radiates fromall bodiesin straight lines, and in alldirections.
It strikes most powerfully indirect lines.
Its rays may be collected into afocus, just as the rays of the sun.
It may bereflectedfrom a polished surface.
It is more easilyconductedby some substances than by others.
"For my days are consumed like smoke, and my bones are burned as an hearth."—Psalm cii.
87.What is animal heat?
Animal heat is derived from the slow combustion ofcarbonin the blood of animals with theoxygenof the air which the animals breathe.
88.What is latent heat?
Latent heat (or more properlylatent caloric) is that which exists, in some degree, in allbodies, though it may be imperceptible to thesenses.
89.Is there latent caloric in ice, snow, water, marble, &c?
Yes; there is some amount ofcaloricin all substances.
A blacksmith may hammer a small piece of iron until it becomesred hot. With this he may light a match, andkindle the fire of his forge. The iron has become more dense by the hammering, and it cannot again be heated to the same degree by similar means, until it has been exposedin fire, toa red heat. Is it not possible that, by hammering, the particles of iron have been driven closer together, andthe latent heatdriven out? No further hammering will force the atoms nearer, and therefore no further heat can be developed. But when the iron hasagain absorbed caloric, by being plunged in a fire, it is again charged with latent heat. Indians producesparksby rubbing togethertwo pieces of wood. Two pieces of ice may be rubbed together until sufficient warmth is developed tomelt them both. The axles of railway carriages frequently becomered hotfromfriction.
90.Have vegetables heat?
Yes; whenever oxygen combines with carbon to form carbonic acid gas, an extrication of heat takes place, however minute the amount. Such a combination occurs much more extensively during the germination of seeds and the impregnation of flowers, than at any other time. In the germination of barley heaped in rooms, previous to being converted into malt, it is well known that aconsiderable amount of heat is developed.
91.Has any investigation of this subject ever been carefully made?
Yes. Lamarck, Senebier, and De Candolle, found the flowers of theArum Maculatum, between three and seven o'clock in the afternoon, as much as 7 deg. Reaum. warmer than the external air. Schultz found a difference of 4 deg. to 5 deg. between the heat of the spathe of theCanadian pinnatifoliumand the surroundingair, at six to seven o'clock p.m. Other observations have established differences of as much as 30 deg. between the temperature of the spathe of theArum cordifolium, and that of the surrounding atmosphere.
"And there are diversities of operations, but it is the same God which worketh in all."—Corinthians xii.
92.Have plants sometimes a temperature lower than that of the surrounding air?
Yes. It has not only been found that under particular circumstances the heat of certain parts of plants is elevated to a very remarkable degree, but that, under nearly all circumstances, they have a temperature different from that of the external air, beingwarmer in winter, and cooler in summer.
93.How many kinds of combustion are there?
There arethree, viz., slow oxydation,when little or no light is evolved; a more rapid combination,when the heat is so great as to become luminous; and a still more energetic action,when it bursts into flame.
94.Why does phosphorous look luminous?
Because it is undergoing slowcombustion.
95.Why do decayed wood, and putrifying fish, look luminous?
Because they are undergoing slowcombustion. In these cases the heat and light evolved are at no one time very considerable. But thetotal amount of heat, and probably oflight, generated through the lengthy period of this slow oxydation,amounts to exactly the same as would be evolved during the most rapid combustion of the same substances.
96.What is flame?
It is gaseous matter burning at avery high temperature.
97.Why, when we put fresh coals upon a fire, do we hear the gas escaping from the coals without taking fire?
Because, the fire being slow, the temperature is not high enough to ignite the gas.
"I will praise thee, O Lord, with my whole heart; I will show forth thy marvellous work."—Psalm ix.
98.What is the gas which escapes from the coals?
Carburetted hydrogen.
99.Why, if we light a piece of paper, and lay it where the gas is escaping from the coals, will it burst into flame?
Because the lighted paper gives aheat sufficientto ignite the gas; and because also hydrogen requires the contact offlameto ignite it.
100.Why, when the coals have become heated, will the hydrogen burst into flame?
Because thecarbonof the coals, and theoxygenof the air, have begun to combine, and have greatly increased theheat, and have produced a rapid combustion,so nearly allied to flame, that itignites the hydrogen.
101.What temperature is required to produce flame?
That depends upon the nature of the combustible you desire to burn. Finely divided phosphorous and phosphorated hydrogen will take fire at a temperature of 60 deg. or 70 deg.; solid phosphorous at 140 deg.; sulphur at 500 deg.; hydrogen and carbonic oxide at 1,000 deg. (red heat); coal gas, ether, turpentine, alcohol, tallow, and wood, at about 2,000 deg. (incipient white heat). When once inflamed they willcontinue to burn, and will maintain a very high temperature.
102.What is smoke?
Smoke consists of small particles ofcarbonofhydrogen gas, andother volatile matters, which are driven off by heat and carried up the chimney.
103.Is it not a waste of fuel to allow this matter to escape?
It is, as it might all be burnt up by better management.
104.How may the waste be avoided?
By putting on only a little coals at a time, so that the heat of the fire shall be sufficient to consume these volatile matters as they escape.
"And the strong shall be as tow, and the maker of it as a spark, and they shall both burn together, and none shall quench them."—Isaiah i.
105.Why is there so little smoke when the fire is red?
Because thehydrogenand thevolatileparts of thecoalhave already been driven off and consumed, and the combustion that continues is principally caused by thecarbonof the coals, and the oxygen of the air.
106.Will carbon, burnt in oxygen, produce flame and smoke?
It burns brightly, but it produces neither flame nor smoke.
107.Why do not charcoal and coke fires give flame?
Because thehydrogenhas been driven off by the processes by which charcoal and coke are made.
108.What is a conductor of heat?
A conductor of heat is any substance through which heat isreadily transmitted.
109.What is a non-conductor of heat?
A non-conductor is any substance through which heat willnotpass readily.
110.Name a few good conductors.
Gold, silver, copper, platinum, iron, zinc, tin, stone,and all dense solid bodies.
111.Name a few non-conductors.
Fur, wool, down, wood, cotton, paper, andall substances of a spongy or porous texture.
112.How is heat transmitted from one body to another?
By Conduction, Radiation, Reflection, Absorption and Convection.
113.What is the Conduction of heat?
It is the communication of heat from one body to anotherby contact. If I lay a penny piece upon the hob, it becomes hot byconduction.
114.What is the Radiation of heat?
The transmission of heat by aseries of rays. If I hold my handbefore the fire, the rays of heat fall upon it, andmy hand receives the heat through radiation.
"Sing praises to the Lord, which dwelleth in Zion, declare among the people his doings."—Psalm ix.
115.What is the Reflection of heat?
The reflection of heat is thethrowing backof its rays towards the direction whence they came. In a Dutch oven the rays of heat pass from the fire to the oven, and arereflectedback again bythe bright surface of the tin. There is, therefore, considerable economy of heat in ovens, and other cooking utensils constructed upon this plan.
116.What is the Absorption of heat?
The absorption of heat is the taking of it up by the body to which it is transmitted or conducted. Heat was conveyed to my hand byradiation, andtaken upby my hand byabsorption.
117.What is the Convection of heat?
The convection of heat is the transmission of itthrougha body or a number of bodies, or particles of bodies, by those substances whichfirst received it; as when hot water rises from the bottom of a kettle and imparts heat to the cold water lying above it.
118.Why does not a piece of wood which is turning at one end, feel hot at the other end?
Because wood isa bad conductor of heat.
119.Why is wood a bad conductor of heat?
Because the arrangement of the particles of which it is composed does not favour the transmission ofcaloric.
120.Why do some articles of clothing feel cold, and others warm?
Because some are bad conductors of heat,and do not draw off much of the warmth of our bodies; while others arebetter conductors, andtake up a larger portion of our warmth.
"The fining pot is for silver, and the furnace for gold: but the Lord trieth the hearts."—Proverbs xvii.
121.Which feels the warmer, the conductor or non-conductor?
The non-conductor, as it does not readilyabsorbthe warmth of our bodies.
122.What substances are the best conductors of heat?
Gold, silver, copper, and most substances of close and hard formation, &c.
123.What substances are the worst conductors of heat?
Fur, eider down, feathers, raw silk, wood, lamp-black, cotton, soot, charcoal, &c.
124.Why has the toasting-fork a wooden handle?
Because wood is notso good a conductoras metal, therefore the wood prevents the heat from being transmittedby conductionto our hands.
125.Why has the coffee-pot a wooden handle?
Because the metal of the coffee-pot would otherwiseconduct the heat to the hand; but wood,being a bad conductor, prevents it.
126.Why does hot water in a metal jug feel hotter than in an earthenware one?
Because metal, being a good conductor,readily delivers heat to the hand; butearthenware, being an indifferent conductor, parts with the heat slowly.
127.How can we ascertain that wood prevents the conduction of heat to the hand?
By passing the top of the finger along the wooden handle of the coffee-pot, until it reaches the point where the wood meets the metal. The wooden handle will be found to becool, but the metal will feelvery hot.
128.Of what use are kettle-holders?
Being made ofbad conductors, such as wood, paper, or woollen cloth, they will not readilyconductthe heat from the kettle to the hand.
"Wisdom is the principal thing; therefore get wisdom: and with all thy getting get understanding."—Proverbs iv.
129.Will a kettle-holder, being a bad conductor, sometimes conduct heat to the hand?
Yes. But so slowly that the hand will notfeel the inconvenience of too much heat.
130.Why does hot metal feel hotter than heated wool, though they may both be of the same degree of temperature?
Because metal gives out heatmore rapidly than wool, by which it is mademore perceptible to our feelings.
131.Which would become cold first—the metal or the wool?
Thewool, because, although the metal conducts heat more rapidly, to a substance in contact with it, it does notradiate heatas well as ablack and rough substance.
132.Why do iron articles feel intensely cold in winter?
Because iron is one of the best conductors, and draws off heat from the hand very rapidly.
133.What is the cause of the sensation called cold?
When we feel cold, heat is beingdrawn off from our bodies.
134.What is the cause of the sensation called heat?
When we feel hot, our bodies areabsorbing heatfrom external causes.
The condition here implied is that of health, and of ordinary circumstances. A person in a condition of fever, suffering from intense heat arising from a diseased state of the blood, could not be said to beabsorbing heat. Nor could such a description apply to a person who, by a very rapid walk, has raised the temperature of his body considerably above its natural state, by theinternal combustionwhich has already been described. A person feeling hot in bed, from excessive clothes, feels hot from thedevelopment of heat internally, which is notconducted awaywith sufficient rapidity to maintain the natural temperature of the body.
135.If a person, sitting before a fire-place, without a fire, were to set one foot upon a rug, and the other upon the stone hearth, which would feel the colder?
The foot on the stone, because stone is a good conductor, and wouldconduct the warmth of the foot away from it.
"The earth is the Lord's, and the fulness thereof; the world, and they that dwell therein."—Psalm xxiv.
136.What does the hearth-stone do with the heat that it receives?
It delivers it to the surrounding air, and to any other bodies with which it may bein contact—and as it parts with heat,it takes up more from any body hotter than itself.
137.When there is no fire in a room, what is the relative temperature of the various things in the room?
They are all of the same temperature.
138.If all the articles in the room are of the same temperature, why do some feel colder than others?
Because they differ in their relative powers ofconduction. Those that are the best conductors feel coldest, as they convey away the heat of the hand most rapidly.
If you lay your hand upon thewoollen table cover, or upon thesleeve of your coator mantle, it will feelneither warm nor cold, under ordinary circumstances. But if you raise your hand from the table cover, or coat, and lay it on the marble mantel piece, the mantel-piece will feelcold. If now you return your hand from the mantel-piece to the table cover or coat,a sensation of warmth will become distinctly perceptible. This will afford a good conception of the relativepowers of conduction of wool and marble.
139.How long does a substance feel cold or hot to the touch?
Until it has brought the part touching it to the same temperature as itself.
140.When do substances feel neither hot nor cold?
When they are of the same temperature as our bodies.
141.Why, under these circumstances, do they feel neither hot nor cold?
Because they neither take heat from, nor supply it to, the body.
142.Which would feel the warmer, when the fire was lighted, the hearth-rug or the hearth-stone?
The hearth-stone, because it is agood conductor, and would not onlyreceive heatreadily, but wouldpart with it as freely(therebymaking its heatperceptible). But the hearth-rug,being a bad conductor, would part with its heat very slowly, and it would therefore beless perceptible.
"Fire and hail; snow and vapour; stormy wind fulfilling his word."—Psalm cxlviii.
143.Would the hearth-stone feel hotter than the hearth-rug though both were of the same temperature?
It would feelhotter than the hearth-rug, because it would part with its heat so rapidly that it would be themore perceptible.
144.But if the hearth-stone and the hearth-rug were both colder than the hand, which would feel the colder of the two?
Then the hearth-stone would feel the colder, because,being a good conductor, it wouldtake heatfrom the hand more freely than the hearth-rug, which is abad conductor.
145.Why would the hearth-stone feel comparatively hotter in the one case, and colder in the other?
Because,being a good conductor, it would conduct heat rapidlytothe hand when hot, and take heat rapidlyfromthe hand when cold.