The Wilkinsons were having a small party,—it consisted of themselves and
Uncle Bagges—at which the younger members of the family, home for the
holidays, had been just admitted to assist after dinner. Uncle Bagges
was a gentleman from whom his affectionate relatives cherished
expectations of a testamentary nature. Hence the greatest attention was
paid by them to the wishes of Mr. Bagges, as well as to every
observation which he might be pleased to make.
“Eh! what? you sir,” said Mr. Bagges, facetiously addressing himself to
his eldest nephew, Harry,—“Eh! what? I am glad to hear, sir, that you
are doing well at school. Now—eh? now, are you clever enough to tell me
where was Moses when he put the candle out?”
“That depends, uncle,” answered the young gentleman, “on whether he had
lighted the candle to see with at night, or by daylight, to seal a
letter.”
“Eh! Very good, now! ’Pon my word, very good,” exclaimed Uncle Bagges.
“You must be Lord Chancellor, sir—Lord Chancellor, one of these days.”
“And now, uncle,” asked Harry, who was a favourite with the old
gentleman, “can you tell me what you do when you put a candle out?”
“Clap an extinguisher on it, you young rogue, to be sure.”
“Oh! but I mean, you cut off its supply of oxygen,” said Master Harry.
“Cut off its ox’s—eh? what? I shall cut off your nose, you young dog,
one of these fine days.”
“He means something he heard at the Royal Institution,” observed Mrs.
Wilkinson. “He reads a great deal about chemistry, and he attended
Professor Faraday’s lectures there on the chemical history of a candle,
and has been full of it ever since.”
“Now, you sir,” said Uncle Bagges, “come you here to me, and tell me
what you have to say about this chemical, eh?—or comical; which?—this
comical chemical history of a candle.”
“He’ll bore you, Bagges,” said Mr. Wilkinson. “Harry, don’t be
troublesome to your uncle.”
“Troublesome! Oh, not at all. He amuses me. I like to hear him. So let
him teach his old uncle the comicality and chemicality of a farthing
rushlight.”
“A wax candle will be nicer and cleaner, uncle, and answer the same
purpose. There’s one on the mantel-shelf. Let me light it.”
“Take care you don’t burn your fingers, or set anything on fire,” said
Mrs. Wilkinson.
“Now, uncle,” commenced Harry, having drawn his chair to the side of Mr.
Bagges, “we have got our candle burning. What do you see?”
“Let me put on my spectacles,” answered the uncle.
“Look down on the top of the candle around the wick. See, it is a little
cup full of melted wax. The heat of the flame has melted the wax just
round the wick. The cold air keeps the outside of it hard, so as to make
the rim of it. The melted wax in the little cup goes up through the wick
to be burnt, just as oil does in the wick of a lamp. What do you think
makes it go up, uncle?”
“Why—why, the flame draws it up, doesn’t it?”
“Not exactly, uncle. It goes up through little tiny passages in the
cotton wick, because very, very small channels, or pipes, or pores, have
the power in themselves of sucking up liquids. What they do it by is
called cap—something.”
“Capillary attraction, Harry,” suggested Mr. Wilkinson.
“Yes, that’s it; just as a sponge sucks up water, or a bit of lump-sugar
the little drop of tea or coffee left in the bottom of a cup. But I
mustn’t say much more about this, or else you will tell me I am doing
something very much like teaching my grandmother to—you know what.”
“Your grandmother, eh, young sharpshins?”
“No—I mean my uncle. Now, I’ll blow the candle out, like Moses; not to
be in the dark, though, but to see into what it is. Look at the smoke
rising from the wick. I’ll hold a bit of lighted paper in the smoke, so
as not to touch the wick. But see, for all that, the candle lights
again. So this shows that the melted wax sucked up through the wick is
turned into vapour; and the vapour burns. The heat of the burning vapour
keeps on melting more wax, and that is sucked up too within the flame,
and turned into vapour, and burnt, and so on till the wax is all used
up, and the candle is gone. So the flame, uncle, you see, is the last of
the candle, and the candle seems to go through the flame into
nothing—although it doesn’t, but goes into several things, and isn’t it
curious, as Professor Faraday said, that the candle should look so
splendid and glorious in going away?”
“How well he remembers, doesn’t he?” observed Mrs. Wilkinson.
“I dare say,” proceeded Harry, “that the flame of the candle looks flat
to you; but if we were to put a lamp glass over it, so as to shelter it
from the draught, you would see it is round,—round sideways, and running
up to a peak. It is drawn up by the hot air; you know that hot air
always rises, and that is the way smoke is taken up the chimney. What
should you think was in the middle of the flame?”
“I should say, fire,” replied Uncle Bagges.
“Oh, no! The flame is hollow. The bright flame we see is something no
thicker than a thin peel, or skin; and it doesn’t touch the wick. Inside
of it is the vapour I told you of just now. If you put one end of a bent
pipe into the middle of the flame, and let the other end of the pipe dip
into a bottle, the vapour or gas from the candle will mix with the air
there; and if you set fire to the mixture of gas from the candle and air
in the bottle, it would go off with a bang.”
“I wish you’d do that, Harry,” said Master Tom, the younger brother of
the juvenile lecturer.
“I want the proper things,” answered Harry. “Well, uncle, the flame of
the candle is a little shining case, with gas in the inside of it, and
air on the outside, so that the case of flame is between the air and the
gas. The gas keeps going into the flame to burn, and when the candle
burns properly, none of it ever passes out through the flame; and none
of the air ever gets in through the flame to the gas. The greatest heat
of the candle is in this skin, or peel, or case of flame.”
“Case of flame!” repeated Mr. Bagges. “Live and learn. I should have
thought a candle-flame was as thick as my poor old noddle.”
“I can show you the contrary,” said Harry. “I take this piece of white
paper, look, and hold it a second or two down upon the candle-flame,
keeping the flame very steady. Now I’ll rub off the black of the smoke,
and—there—you find that the paper is scorched in the shape of a ring;
but inside the ring it is only dirtied, and not singed at all.”
“Seeing is believing,” remarked the uncle.
“But,” proceeded Harry, “there is more in the candle-flame than the gas
that comes out of the candle. You know a candle won’t burn without air.
There must be always air around the gas, and touching it like, to make
it burn. If a candle hasn’t got enough air, it goes out, or burns badly,
so that some of the vapour inside of the flame comes out through it in
the form of smoke, and this is the reason of a candle smoking. So now
you know why a great clumsy dip smokes more than a neat wax candle; it
is because the thick wick of the dip makes too much fuel in proportion
to the air that can get to it.”
“Dear me! Well, I suppose there is a reason for everything,” exclaimed
the young philosopher’s mamma.
“What should you say, now,” continued Harry, “if I told you that the
smoke that comes out of a candle is the very thing that makes a candle
light? Yes; a candle shines by consuming its own smoke. The smoke of a
candle is a cloud of small dust, and the little grains of the dust are
bits of charcoal, or carbon, as chemists call it. They are made in the
flame, and burnt in the flame, and, while burning, make the flame
bright. They are burnt the moment they are made; but the flame goes on
making more of them as fast as it burns them; and that is how it keeps
bright. The place they are made in, is in the case of flame itself,
where the strongest heat is. The great heat separates them from the gas
which comes from the melted wax, and, as soon as they touch the air on
the outside of the thin case of flame, they burn.”
“Can you tell how it is that the little bits of carbon cause the
brightness of the flame?” asked Mr. Wilkinson.
“Because they are pieces of solid matter,” answered Harry. “To make a
flame shine, there must always be some solid—or at least liquid—matter
in it.”
“Very good,” said Mr. Bagges,—“solid stuff necessary to brightness.”
“Some gases and other things,” resumed Harry, “that burn with a flame
you can hardly see, burn splendidly when something solid is put into
them. Oxygen and hydrogen—tell me if I use too hard words, uncle—oxygen
and hydrogen gases, if mixed together and blown through a pipe, burn
with plenty of heat but with very little light. But if their flame is
blown upon a piece of quicklime, it gets so bright as to be quite
dazzling. Make the smoke of oil of turpentine pass through the same
flame, and it gives the flame a beautiful brightness directly.”
“I wonder,” observed Uncle Bagges, “what has made you such a bright
youth.”
“Taking after uncle, perhaps,” retorted his nephew. “Don’t put my candle
and me out. Well, carbon or charcoal is what causes the brightness of
all lamps, and candles, and other common lights; so, of course, there is
carbon in what they are all made of.”
“So carbon is smoke, eh? and light is owing to your carbon. Giving light
out of smoke, eh? as they say in the classics,” observed Mr. Bagges.
“But what becomes of the candle,” pursued Harry, “as it burns away?
where does it go?”
“Nowhere,” said his mamma, “I should think. It burns to nothing.”
“Oh, dear, no!” said Harry, “everything—everybody goes somewhere.”
“Eh!—rather an important consideration that,” Mr. Bagges moralised.
“You can see it goes into smoke, which makes soot for one thing,”
pursued Harry. “There are other things it goes into, not to be seen by
only looking, but you can get to see them by taking the right
means,—just put your hand over the candle, uncle.”
“Thank you, young gentleman, I had rather be excused.”
“Not close enough down to burn you, uncle; higher up. There,—you feel a
stream of hot air; so something seems to rise from the candle. Suppose
you were to put a very long slender gas-burner over the flame, and let
the flame burn just within the end of it, as if it were a chimney,—some
of the hot steam would go up and come out at the top, but a sort of dew
would be left behind in the glass chimney, if the chimney was cold
enough when you put it on. There are ways of collecting this sort of
dew, and when it is collected it turns out to be really water. I am not
joking, uncle. Water is one of the things which the candle turns into in
burning,—water coming out of fire. A jet of oil gives above a pint of
water in burning. In some lighthouses they burn, Professor Faraday says,
up to two gallons of oil in a night, and if the windows are cold the
steam from the oil clouds the inside of the windows, and, in frosty
weather, freezes into ice.”
“Water out of a candle, eh?” exclaimed Mr. Bagges. “As hard to get, I
should have thought, as blood out of a post. Where does it come from?”
“Part from the wax, and part from the air, and yet not a drop of it
comes either from the air or the wax. What do you make of that, uncle?”
“Eh? Oh! I’m no hand at riddles. Give it up.”
“No riddle at all, uncle. The part that comes from the wax isn’t water,
and the part that comes from the air isn’t water, but when put together
they become water. Water is a mixture of two things, then. This can be
shown. Put some iron wire or turnings into a gun-barrel open at both
ends. Heat the middle of the barrel red-hot in a little furnace. Keep
the heat up, and send the steam of boiling water through the red-hot
gun-barrel. What will come out at the other end of the barrel won’t be
steam; it will be gas, which doesn’t turn to water again when it gets
cold, and which burns if you put a light to it. Take the turnings out of
the gun-barrel, and you will find them changed to rust, and heavier than
when they were put in. Part of the water is the gas that comes out of
the barrel, the other part is what mixes with the iron turnings, and
changes them to rust, and makes them heavier. You can fill a bladder
with the gas that comes out of the gun-barrel, or you can pass bubbles
of it up into a jar of water turned upside down in a trough, and, as I
said, you can make this part of the water burn.”
“Eh?” cried Mr. Bagges. “Upon my word! One of these days, we shall have
you setting the Thames on fire.”
“Nothing more easy,” said Harry, “than to burn part of the Thames, or of
any other water; I mean the gas that I have just told you about, which
is called hydrogen. In burning, hydrogen produces water again, like the
flame of the candle. Indeed, hydrogen is that part of the water, formed
by a candle burning, that comes from the wax. All things that have
hydrogen in them produce water in burning, and the more there is in them
the more they produce. When pure hydrogen burns, nothing comes from it
but water, no smoke or soot at all. If you were to burn one ounce of it,
the water you would get would be just nine ounces. There are many ways
of making hydrogen, besides out of steam by the hot gun-barrel. I could
show it you in a moment by pouring a little sulphuric acid mixed with
water into a bottle upon a few zinc or steel filings, and putting a cork
in the bottle with a little pipe through it, and setting fire to the gas
that would come from the mouth of the pipe. We should find the flame
very hot, but having scarcely any brightness. I should like you to see
the curious qualities of hydrogen, particularly how light it is, so as
to carry things up in the air; and I wish I had a small balloon to fill
with it and make go up to the ceiling, or a bag-pipe full of it to blow
soap-bubbles with, and show how much faster they rise than common ones,
blown with the breath.”
“So do I,” interposed Master Tom.
“And so,” resumed Harry, “hydrogen, you know, uncle, is part of water,
and just one-ninth part.”
“As hydrogen is to water, so is a tailor to an ordinary individual, eh?”
Mr. Bagges remarked.
“Well, now then, uncle, if hydrogen is the tailor’s part of the water,
what are the other eight parts? The iron turnings used to make hydrogen
in the gun-barrel, and rusted, take just those eight parts from the
water in the shape of steam, and are so much the heavier. Burn iron
turnings in the air, and they make the same rust, and gain just the same
in weight. So the other eight parts must be found in the air for one
thing, and in the rusted iron turnings for another, and they must also
be in the water; and now the question is, how to get at them?”
“Out of the water? Fish for them, I should say,” suggested Mr. Bagges.
“Why, so we can,” said Harry. “Only, instead of hooks and lines, we must
use wires—two wires, one from one end, the other from the other, of a
galvanic battery. Put the points of these wires into water, a little
distance apart, and they instantly take the water to pieces. If they are
of copper, or a metal that will rust easily, one of them begins to rust,
and air-bubbles come up from the other. These bubbles are hydrogen. The
other part of the water mixes with the end of the wire and makes rust.
But if the wires are of gold, or a metal that does not rust easily,
air-bubbles rise from the ends of both wires. Collect the bubbles from
both wires in a tube, and fire them, and they turn to water again; and
this water is exactly the same weight as the quantity that has been
changed into the two gases. Now then, uncle, what should you think water
was composed of?”
“Eh? well—I suppose of those very identical two gases, young gentleman.”
“Right, uncle. Recollect that the gas from one of the wires was
hydrogen, the one-ninth of water. What should you guess the gas from the
other wire to be?”
“Stop—eh?—wait a bit—eh?—oh!—why, the other eight-ninths, to be sure.”
“Good again, uncle. Now this gas that is eight-ninths of water is the
gas called oxygen that I mentioned just now. This is a very curious gas.
It won’t burn in air at all itself, like gas from a lamp, but it has a
wonderful power of making things burn that are lighted and put into it.
If you fill a jar with it——”
“How do you manage that?” Mr. Bagges inquired.
“You fill the jar with water,” answered Harry, “and you stand it upside
down in a vessel full of water too. Then you let bubbles of the gas up
into the jar and they turn out the water and take its place. Put a
stopper in the neck of the jar, or hold a glass plate against the mouth
of it, and you can take it out of the water and so have bottled oxygen.
A lighted candle put into a jar of oxygen blazes up directly and is
consumed before you can say Jack Robinson. Charcoal burns away in it as
fast, with beautiful bright sparks—phosphorus with a light that dazzles
you to look at—and a piece of iron or steel just made red-hot at the end
first, is burnt in oxygen quicker than a stick would be in common air.
The experiment of burning things in oxygen beats any fire-works.”
“Oh, how jolly!” exclaimed Tom.
“Now we see, uncle,” Harry continued, “that water is hydrogen and oxygen
united together, that water is got wherever hydrogen is burnt in common
air, that a candle won’t burn without air, and that when a candle burns
there is hydrogen in it burning, and forming water. Now, then, where
does the hydrogen of the candle get the oxygen from, to turn into water
with it?”
“From the air, eh?”
“Just so. I can’t stop to tell you of the other things which there is
oxygen in, and the many beautiful and amusing ways of getting it. But as
there is oxygen in the air, and as oxygen makes things burn at such a
rate, perhaps you wonder why air does not make things burn as fast as
oxygen. The reason is, that there is something else in the air that
mixes with the oxygen and weakens it.”
“Makes a sort of gaseous grog of it, eh?” said Mr. Bagges. “But how is
that proved?”
“Why, there is a gas, called nitrous gas, which, if you mix it with
oxygen, takes all the oxygen into itself, and the mixture of the nitrous
gas and oxygen, if you put water with it, goes into the water. Mix
nitrous gas and air together in a jar over water, and the nitrous gas
takes away the oxygen, and then the water sucks up the mixed oxygen and
nitrous gas, and that part of the air which weakens the oxygen is left
behind. Burning phosphorus in confined air will also take all the oxygen
from it, and there are other ways of doing the same thing. The portion
of the air left behind is called nitrogen. You wouldn’t know it from
common air by the look; it has no colour, taste, nor smell, and it won’t
burn. But things won’t burn in it, either; and anything on fire put into
it goes out directly. It isn’t fit to breathe,—and a mouse, or any
animal, shut up in it, dies. It isn’t poisonous, though; creatures only
die in it for want of oxygen. We breathe it with oxygen, and then it
does no harm, but good; for if we breathed pure oxygen, we should
breathe away so violently, that we should soon breathe our life out. In
the same way, if the air were nothing but oxygen, a candle would not
last above a minute.”
“What a tallow-chandler’s bill we should have!” remarked Mrs. Wilkinson.
“‘If a house were on fire in oxygen,’ as Professor Faraday said, ‘every
iron bar, or rafter, or pillar, every nail and iron tool, and the
fire-place itself; all the zinc and copper roofs, and leaden coverings,
and gutters, and pipes, would consume and burn, increasing the
combustion.’”
“That would be, indeed, burning ‘like a house on fire,’” observed Mr.
Bagges.
“‘Think,’” said Harry, continuing his quotation, “‘of the Houses of
Parliament, or a steam-engine manufactory. Think of an iron-proof
chest—no proof against oxygen. Think of a locomotive and its
train,—every engine, every carriage, and even every rail would be set on
fire and burnt up.’ So now, uncle, I think you see what the use of
nitrogen is, and especially how it prevents a candle from burning out
too fast.”
“Eh?” said Mr. Bagges. “Well, I will say I do think we are under
considerable obligations to nitrogen.”
“I have explained to you, uncle,” pursued Harry, “how a candle, in
burning, turns into water. But it turns into something else besides
that; there is a stream of hot air going up from it that won’t condense
into dew; some of that is the nitrogen of the air which the candle has
taken all the oxygen from. But there is more in it than nitrogen. Hold a
long glass tube over a candle, so that the stream of hot air from it may
go up through the tube. Hold a jar over the end of the tube to collect
some of the stream of hot air. Put some lime-water, which looks quite
clear, into the jar; stop the jar, and shake it up. The lime-water,
which was quite clear before, turns milky. Then there is something made
by the burning of the candle that changes the colour of the lime-water.
That is a gas, too, and you can collect it, and examine it. It is to be
got from several things, and is a part of all chalk, marble, and the
shells of eggs or of shell-fish. The easiest way to make it is by
pouring muriatic or sulphuric acid on chalk or marble. The marble or
chalk begins to hiss or bubble, and you can collect the bubbles in the
same way that you can oxygen. The gas made by the candle in burning, and
which also is got out of the chalk and marble, is called carbonic acid.
It puts out a light in a moment; it kills any animal that breathes it,
and it is really poisonous to breathe, because it destroys life even
when mixed with a pretty large quantity of common air. The bubbles made
by beer when it ferments, are carbonic acid, so is the air that fizzes
out of soda-water,—and it is good to swallow though it is deadly to
breathe. It is got from chalk by burning the chalk as well as by putting
acid to it, and burning the carbonic acid out of chalk makes the chalk
lime. This is why people are killed sometimes by getting in the way of
the wind that blows from lime-kilns.”
“Of which it is advisable carefully to keep to the windward,” Mr.
Wilkinson observed.
“The most curious thing about carbonic acid gas,” proceeded Harry, “is
its weight. Although it is only a sort of air, it is so heavy that you
can pour it from one vessel into another. You may dip a cup of it and
pour it down upon a candle, and it will put the candle out, which would
astonish an ignorant person; because carbonic acid gas is as invisible
as the air, and the candle seems to be put out by nothing. A soap-bubble
or common air floats on it like wood on water. Its weight is what makes
it collect in brewers’ vats; and also in wells, where it is produced
naturally; and owing to its collecting in such places it causes the
deaths we so often hear about of those who go down into them without
proper care. It is found in many springs of water, more or less; and a
great deal of it comes out of the earth in some places. Carbonic acid
gas is what stupifies the dogs in the Grotto del Cane. Well, but how is
carbonic acid gas made by the candle?”
“I hope with your candle you you’ll throw some light upon the subject,”
said Uncle Bagges.
“I hope so,” answered Harry. “Recollect it is the burning of the smoke,
or soot, or carbon of the candle that makes the candle-flame bright.
Also that the candle won’t burn without air. Likewise that it will not
burn in nitrogen, or air that has been deprived of oxygen. So the carbon
of the candle mingles with oxygen, in burning, to make carbonic acid
gas, just as the hydrogen does to form water. Carbonic acid gas, then,
is carbon or charcoal dissolved in oxygen. Here is black soot getting
invisible and changing into air; and this seems strange, uncle, doesn’t
it?”
“Ahem! Strange, if true,” answered Mr. Bagges. “Eh?—well! I suppose it’s
all right.”
“Quite so, uncle. Burn carbon or charcoal either in the air or in
oxygen, and it is sure always to make carbonic acid, and nothing else,
if it is dry. No dew or mist gathers in a cold glass jar if you burn dry
charcoal in it. The charcoal goes entirely into carbonic acid gas, and
leaves nothing behind but ashes, which are only earthy stuff that was in
the charcoal, but not part of the charcoal itself. And now, shall I tell
you something about carbon?”
“With all my heart,” assented Mr. Bagges.
“I said that there was carbon or charcoal in all common lights,—so there
is in every common kind of fuel. If you heat coal or wood away from the
air, some gas comes away, and leaves behind coke from coal, and charcoal
from wood; both carbon, though not pure. Heat carbon as much as you will
in a close vessel, and it does not change in the least; but let the air
get to it, and then it burns and flies off in carbonic acid gas. This
makes carbon so convenient for fuel. But it is ornamental as well as
useful, uncle. The diamond is nothing else than carbon.”
“The diamond, eh? You mean the black diamond.”
“No; the diamond, really and truly. The diamond is only carbon in the
shape of a crystal.”
“Eh? and can’t some of your clever chemists crystallise a little bit of
carbon, and make a Koh-i-noor?”
“Ah, uncle, perhaps we shall, some day. In the meantime I suppose we
must be content with making carbon so brilliant as it is in the flame of
a candle. Well; now you see that a candle-flame is vapour burning, and
the vapour, in burning, turns into water and carbonic acid gas. The
oxygen of both the carbonic acid gas and the water comes from the air,
and the hydrogen and carbon together are the vapour. They are distilled
out of the melted wax by the heat. But, you know, carbon alone can’t be
distilled by any heat. It can be distilled, though, when it is joined
with hydrogen, as it is in the wax, and then the mixed hydrogen and
carbon rise in gas of the same kind as the gas in the streets, and that
also is distilled by heat from coal. So a candle is a little gas
manufactory in itself, that burns the gas as fast as it makes it.”
“Haven’t you pretty nearly come to your candle’s end?” said Mr.
Wilkinson.
“Nearly. I only want to tell uncle, that the burning of a candle is
almost exactly like our breathing. Breathing is consuming oxygen, only
not so fast as burning. In breathing we throw out water in vapour and
carbonic acid from our lungs, and take oxygen in. Oxygen is as necessary
to support the life of the body, as it is to keep up the flame of a
candle.”
“So,” said Mr. Bagges, “man is a candle, eh? and Shakespeare knew that,
I suppose, (as he did most things,) when he wrote—
‘Out, out, brief candle!’
“Well, well; we old ones are moulds, and you young squires are dips and
rushlights, eh? Any more to tell us about the candle?”
“I could tell you a great deal more about oxygen, and hydrogen, and
carbon, and water, and breathing, that Professor Faraday said, if I had
time; but you should go and hear him yourself, uncle.”
“Eh? well! I think I will. Some of us seniors may learn something from a
juvenile lecture, at any rate, if given by a Faraday. And now, my boy, I
will tell you what,” added Mr. Bagges, “I am very glad to find you so
fond of study and science; and you deserve to be encouraged; and so I’ll
give you a what-d’ ye-call-it?—a Galvanic Battery on your next
birth-day; and so much for your teaching your old uncle the chemistry of
a candle.”