When your brother forgets the apples which he has set to roast, what happens to them?

They turn quite black, as you have seen more than once.

It is always black, then, that these things turn, is it not? and a fine rich _charcoaly_ black, as you may see if you please to observe charcoal closely, for just such is the color of little burnt cakes, over-roasted chestnuts, and potatoes in their skins, which have been dropped into the fire.

But there is a common term by which we can express more accurately the misfortune which has befallen all these various things--slices of bread, mutton-chops, apples, cakes, chestnuts, potatoes, and what-not, when "burnt," "over-toasted," "over-roasted," or "over-baked." We may call them _carbonized_, or more simply _charred_ or _charcoaled_; though the word _charred_ is generally used only for burnt _wood_. But _carbon_ being the princ.i.p.al ingredient of _charcoal_, and _charcoal_ being one of the purer forms in which we get at _carbon_, they are almost synonymous terms, and you may call your burnt food _carbonized_, or _charred_, or _charcoaled_, whichever you prefer.

The next question is, how did charcoal or carbon get into the food so as to justify our talking of its being _carbonized_ or _charred_? Even when we use charcoal stoves for cooking, the charcoal does not jump out and get into the mutton-chops, etc., you may be sure. Then it is clear it must have been in them before they were brought to the fire to be cooked; and such is indeed the case, only its black face escaped notice because it was in such gay-looking company, and kept itself hid behind the others like a needle lost in a match-box. Set fire to the matches, and you will soon have nothing left but the needle, which will then strike your eye at once. And so with our burnt food; the fire has carried off all the other ingredients, and the charcoal is left behind alone, exposed to everybody's view, as if on purpose to teach them that it was always there; in the apples, i.e., the potatoes, mutton-chops, etc., which seemed so tempting when the black rogue was hid, but from which now, when he is there by himself, they turn away in disgust.

Charcoal is, in fact, a much more generally distributed substance than you have been used to suppose, dear child. That which comes from burnt wood is most easily observed, because there is a much larger proportion of charcoal in wood than anywhere else; but there is not a morsel, however small, of any animal or vegetable whatsoever, which does not contain charcoal. In the sugar which you crunch, in the wine which you drink, there is charcoal. I could even find some in the water you wash in if I were to try hard. There is charcoal in the goose-quill which I hold in my hand at this moment, and in the paper on which I am writing, and in the handkerchief on my knee. If I hold them all three in the light of my wax taper, I shall soon see them turn black and betray the presence of our friend. It exists in the wax taper itself, as also in the candle, as also in the oil lamp. If I were to hold a piece of flat gla.s.s above their flame, I should collect enough of it to blacken the tip of anybody's nose who presumed to doubt the fact.

There is a portion of it in the air; a portion of it in the earth.

Where is it not? In short, all the stones of all the buildings in the world are filled with it from top to bottom. _Charcoal,_ under his more scientific and important name of _carbon,_ may be called one of the great lords of the world. His domain is so extensive that one might go round the world without getting out of it; he is even worse than the Marquis of Carabas.

After this you will never, I hope, want to persuade me you do not eatcharcoal; for, indeed, you would be puzzled to escape doing so. Of all the things you see on the dinner-table there is but one in which you will not find it--viz., the salt-cellar; and even while saying this, I mean only, in the _salt_ itself, for as to the salt-cellar, clear and transparent as its gla.s.s may be, there is charcoal in it!

Our bodies, therefore, are full of charcoal. Everything that we eat supplies them with enormous quant.i.ties of it, which take up their quarters in every corner of our organs. It is one of the princ.i.p.al materials of the vast collection of structures of which I spoke to you in the early part of these letters, and of which the blood, the steward of the body, is the universal master-builder. If you remember, I told you then that these structures fell to pieces of themselves, in proportion as the workmen went on building, and that the blood, which brings fresh materials on its arrival from the lungs and heart, carries away the refuse ones on its return. And, of all these refuse materials, old charcoal is one of those which takes up the most room, as fresh charcoal took up a great deal of room in the new materials. The blood, as he goes back again, has his pockets quite crammed with it, and if he did not try hard to get rid of it as fast as possible, he would be disabled from being of any further use.

Now it is in the lungs that he clears himself of it. He gives it up to the air, which has need of it for a very interesting operation, of which I shall tell you more by and bye; and in return the air gives him something which is quite indispensable to him, for without it he would not dare to return to the organs, as his authority would no longer be recognised.

In the same way, the charcoal-seller goes to market with his charcoal and receives silver in exchange.

If he were to go home without money his wife would receive him with abuse.

But what is the indispensable thing which the blood obtains in his marketing?

Remember its name well: it is OXYGEN.

And we must speak of it with respect, for we are talking here of a very great and powerful personage, very superior even to CARBON. If CARBON be one of the great lords of the world, OXYGEN is its king.

There is a certain substance, my dear child, of which many people, especially little girls, do not even know the name, but which yet const.i.tutes of itself alone a good half of everything we are acquainted with in the world. And this substance is the very thing I have just named to you. It is OXYGEN.

Ascend into the air as high as you can go, viz., to forty miles or so from the ground, as we said before; _oxygen_ forms the fifth part of that vast aerial ocean which surrounds the globe on every side.

There it is free--is _itself_--if I may use the expression; it is in the condition of _gas_; that is to say, it eludes our sight, though there is no difficulty in ascertaining its presence, when one knows how to set about it.

Go down into the depths of the sea. People think they have good reasons for believing this to be two and a half miles deep on an average, which would give a pretty little sum total of tons for its whole weight, as you will be convinced, if you take the trouble of observing the s.p.a.ce it covers on a map of the world;--to say nothing of lakes, rivers, streams, the water in the clouds, the water scattered throughout the interior or on the surface of continents, including that with which you wash your face every morning.

Oxygen enters in the proportion of eight-ninths into the composition of this incalculable ma.s.s. _Eight-ninths_, you understand, which is very near being the whole nine; in every nine pounds of water there are eight pounds of oxygen, the remainder being left for another substance, of which we shall have occasion to speak presently, and which is called _hydrogen_.

The earth on which you tread is full of oxygen. So far as we have penetrated hitherto into the interior of the globe, we have found king Oxygen everywhere: hidden under a thousand forms, connected with a heap of substances, not one of which could exist without him; imprisoned in a thousand combinations, and always ready to resume his natural condition if his prison-house be destroyed. The whole surface of the earth, plains, hills, mountains, towns, deserts, cultivated fields, everything you would look down upon, if on a clear day you could be carried high enough in a balloon to take in the whole earth at a glance:--all that may be considered as an immense reservoir of oxygen, out of which we should see it escaping in gigantic waves, if some superhuman chemist were to take it into his head to put our poor little globe into a retort of the same kind as chemists use among us. To give you an example; the stones of our fine buildings, in which we have already discovered the presence of _carbon_, are almost half made up of _oxygen_. In a stone which weighs 100 lbs. there are 48 lbs. of oxygen, and the first chemist who pa.s.ses by could make them come out of it if he chose, if he were to use a little trouble and skill.

I enumerated to you last time many of the substances in which _carbon_ is to be found; but as regards _oxygen_ we must give up all attempt at making a list; it would comprehend the whole dictionary. Touch whatever lies under your hand--in your room--in the house--wherever you may go--I will almost defy you to put your finger upon anything--metals excepted--which is not crammed with oxygen. Your very body, to conclude with, would become so small a thing, were the oxygen it contains extracted from it, that you would be perfectly amazed.

So when I told you oxygen was king of the world, I did not say too much, did I? Between ourselves too, it is a great misfortune that people live on so complacently in total ignorance of this all-important material, which is connected with everything, which insinuates itself everywhere, which we make use of every instant of our lives, which may almost be said to be in some sort our very selves, since it const.i.tutes three-fourths of our body, but whose name nevertheless would, I am certain, make many pretty little mouths pout, if one were to utter it in a drawing-room.

This is really the case. Many young ladies who are proud to know who Caractacus was, would be ashamed to know anything about oxygen. There is a foolish notion that women have no business with such subjects, probably because children are supposed not to breathe and mothers are not required to watch over them?

This reminds me that we are on the road to explain _respiration,_ which I had almost forgotten in lifting up this corner of the veil behind which Nature hides her most valuable secrets from the idle and ignorant.

It is _oxygen_ then, which the blood carries off triumphantly from his interview with the air in the cells of the lungs; and, by the way, it is, thanks to this oxygen that it returns from the lungs to the heart, and so from the heart to the organs, with that beautiful rosy tint which distinguishes _arterial_ from _venous_ blood.

Now the blood gives out this oxygen on its road every time it performs the journey, and the perpetual course it performs from the lungs to the organs, and from the organs to the lungs, has for its chief object the perpetual renovation of this previous provision, which is as perpetually consumed.

Do you ask of what use it is? Does the blood leave it at random in our organs, and is it one of the materials with which our steward is constantly providing the little workmen of the body for their various constructions?

No, my dear child. The proverb _"One cannot live upon air,"_ is a very true one, although it is equally true that we cannot live without air. Air does not nourish our organs; on the contrary, it consumes them, and what we eat, serves to supply in precisely the same proportion its insatiable appet.i.te. When we leave off eating, from whatever cause, the air does not leave off too. He goes on always just the same, and that is the reason why people who are starved to death are so thin.

(The air has consumed the vital parts.)

You did not expect this; but now prepare yourself to go on from one surprise to another. To begin with, I shall have to stop here and explain to you before we go any further--can you guess what? Nay, I am sure you cannot; FIRE.

There is not much connection, you will say, between _fire_ and _breathing_.

But there you are mistaken. It is precisely the same thing, as I will prove to you next time.

LETTER XXI.

COMBUSTION.

Have you never, my dear child, whilst warming your little feet on the hearth in winter-time, asked yourself, _What is fire?_ that great benefactor of man; fire, without which part of the world would be uninhabitable by us during at least a third of the year; fire, without which we could not bake a morsel of bread, and would have to eat our meat raw; fire, which lights up the night for us, and without which we should have to go to bed when the hens go to roost; fire, which subdues metals, and without which we should have neither iron, nor copper, nor silver, nor anything that is manufactured from those materials; fire, without which, in short, human industry could not rise to much higher results than that of the monkey and of the beaver?

We are all of us, it is true, so much accustomed to fire that we do not pay much attention to it, and have a sort of persuasion that lucifer matches have existed from all eternity. But the first men, who were nearer neighbors to that great discovery whence all others have originated--the first men treated fire with more respect than we do.

It was to them one of the mighty things of the world. The ancient Persians made a G.o.d of it, and told how Zoroaster, their prophet, went to seek it in heaven, pa.s.sing thither from the top of the Himalayas, the highest chain of mountains in the known world.

The old Greeks pretended that Prometheus stole it from the G.o.ds, to make a present of it to man, which came to nearly the same thing as the Persian account. The Romans had their _sacred fire_, which the celebrated Vestals were bound to keep lighted, on pain of death to whoever should let it go out. At the present day we do not stand upon such ceremonies, but warm our feet at it quite familiarly, without wishing for anything further. But you would see a terrible revolution in the world if some Prometheus reversed were, some fine morning, to steal it from us, and carry it back to its ancient owners. Every branch of human industry would suddenly stop, as if by enchantment, and in the course of a very few years the poor little framework of human society, of which we are now so proud, would totally change its aspect, and the whole world would be turned topsy-turvy.

But do not be alarmed; there is no danger of the sort. Fire is not a present once made to man, but liable to be taken away from him at will.

It is a law of nature which existed before the human race came into being, and which will doubtless continue to exist when the human race shall have disappeared. The existence of fire is connected in the most intimate way with that of that great king of the world of whom we spoke last time--Oxygen. Fire is the wedding-feast of Oxygen with other substances!

When kings are married, what rejoicings there are! what a commotion!

what illuminations! It is only right and proper, then, that the king of the world should have rejoicings and illuminations at his weddings also. And they have never been wanting. The rejoicings are the warmth which rejoices us; the illuminations, the flame which gives us light.

But man, in his dealings with nature, is an imperious subject, such as few earthly kings are troubled with--happily for them! Whenever he wants warmth and light he forces the king of the world to get married, and then takes advantage of the feast; nothing worse than that.

"How so?" you exclaim. "If I want to make a fire with stones or iron, I should never succeed. Is this because oxygen never unites himself with those substances, nor with heaps of others which are equally useless in lighting a fire? Yet you told me that oxygen was to be met with almost everywhere."

It is a fair question, my dear child; but my answer is, that what you said last is precisely the reason why all substances are not fit for making fire of. When oxygen is already there, as he is in stones, for instance, the marriage is over--the feast cannot begin again. Kings are like other people in this respect; their weddings are only celebrated once. If you had happened to be present at the moment when oxygen was united to the materials of which stones are composed, you would have seen a feast of which I should like to have heard some news.

I was not there myself either; but learned men in these latter days have succeeded in breaking the bonds which united oxygen with the primitive substances in certain fragments of stone, and with these substances thus freed, and consequently able to remarry, they have been enabled to give us, in miniature, the spectacle of the festivities of a fresh wedding. And I can a.s.sure you it is enough to make one shudder, to think of the time when such a marriage must have taken place on a large scale.

With regard to _iron_ the case is quite different.

You have without doubt heard tell of Louis XIV. (of France), that proud king who was called _le Grand_, and who is said to have heard himself compared to the sun, without smiling. It seems that he one day took it into his head to marry, it is difficult to say why, with Madame de Maintenon, the old wife of a poor paralytic poet named Scarron, who, as such, however, was only known by some few farces. Do you suppose that the palace of Versailles was illuminated in honor of this marriage?

Not a bit of it. It was a disgraceful marriage, which they were bound to keep secret. The ceremony was conducted mysteriously and without lighting a single candle more than ordinary.

I do not pretend to say that oxygen has any of these weaknesses, nor that he is any more partial to marrying with one body more than with another. In the good G.o.d's great world, outside of the family of man, they know nothing of our foolish pride, of our little weaknesses. It is nevertheless a fact that this dear monarch has his preferences, and that all his marriages are not made in this fashion.

Leave those pretty little scissors of yours, with which you would try in vain to make a fire, outside your window for two or three days, and then observe the dreadful, scaly, red stain which you are sure to find on them afterwards, and which is called _rust._ Have you any idea whence it proceeds? I will tell you. It comes from the oxygen, which has been making one of those cheerless secret marriages with the iron of your scissors. So there have been no pretty sights nor sounds, no lights nor cheerful noises to entertain anybody, and though people may have wished for them ever so much, they have had to do without them.

I will tell you the true reason of these marriages _incognito._ It is because oxygen is but feebly attracted by iron, who does not stand so high in his good graces as many other bodies, and so (to continue the joke) he unites slowly and languidly with him, as we may say.