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 god of it, and told how Zoroaster, their prophet, went to seek it in heaven, passing 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 gods, 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 assure 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 God'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.
Now tell me, when you set fire to a bit of paper, how long does it take to burn?
Half a minute, at the utmost, you answer.
Very good. And how long does it take to produce that rust-stain, even though it is probably not a hundredth part the size of the paper?
Two or three days, is your reply, for so I told you my self.
Here is a strange difference indeed; but from it you may discover why you have not seen any signs of rejoicing or illuminations at the iron wedding. These are always in proportion to the quantity of oxygen which is being married at once—and this was—oh, such a slow affair! When the quantity is very small indeed, the festal illuminations are very small indeed too, and in fact escape observation altogether. In the same way that you would not be conscious of little bits of thread laid delicately one after another on your back, whereas you would plainly feel a large sheet, were it to fall on your shoulders. Yet what is the large sheet but a great quantity of little bits of thread? Only in that case they would all come upon you at once, like the marriage illuminations of burning paper.
Wait a little longer and we shall finish.
What is there, then, in the paper which pleases the oxygen so much that he unites himself to it so readily, and in such large quantities?
What is there? Two substances of high degree, who have actually risen to the dignity of a royal alliance, by the important part they play in the world; one of these, charcoal or carbon, we know quite well already; the other I have only mentioned to you in connection with water, HYDROGEN. Thanks to gas companies, everybody in these days knows hydrogen, at least by name. But before proceeding, I will just tell you that it is by far the lightest body that is known. It is forty and a half times lighter than air, which is not very heavy itself, although in the mass it has its weight, as we have seen.
The true province of hydrogen is water, where it keeps house with oxygen, in proportion of one to eight pounds, as you may remember I stated in my last letter. But beside this, hydrogen and carbon are in a manner inseparable friends, whom one invariably meets side by side in all animal and vegetable substances. In wood, coal, oil, tallow, and spirits of wine; in everything in short that we call combustibles, because the name of combustion has been given to this marriage of oxygen with other bodies, hydrogen and carbon keep themselves shut up very discreetly and very quietly; like two children playing at hide-and-seek. You have sometimes played at hide-and-seek yourself, no doubt? Now, if some naughty child had come behind you with a lighted candle, what would you have done? You would have had to turn out, whether you liked it or not, and be caught. Well! this is what happens to our two friends, when you bring the paper to the fire. The heat forces them out, and the oxygen, which is always at hand, seizes upon them. In a twinkling they are married, and a beautiful flame springs up into the air, which lasts till everything has disappeared.
Hydrogen and carbon! These, then, are the two great combustibles, the two parents of fire; and as nature has lavished them upon us in what we may call inexhaustible quantities; when you hear people lamenting and saying that wood is disappearing, that coal is diminishing, and that the human race will end by not knowing how to warm themselves, do not disturb yourself in the least.
There is more hydrogen in a bucket of water than is wanted to cook a large dinner. There is as much and more carbon in our stone quarries than in our coal pits, and when all the woods in the world are cut down (which I trust will never be!) do you know what we shall do? Why, we shall take to burning the mountains. The Jura mountains in Switzerland, for instance, (to take the most favorable case) are great masses of carbon, without its ever being visible. Everything depends upon knowing how to make it come out of its hiding place; but that will de done when it is wanted: more difficult matters have been accomplished already. As to oxygen, whether carbon comes to him from a log of wood or from a building stone; whether the hydrogen comes from a candle or a glass of water, is a matter of perfect indifference to him. He only considers persons, not their origin, and marries as willingly in one case as in the other.
So we have returned to the subject of respiration, on which I always seem to be turning my back; but now the question is, what brings us to it again? And this is the explanation.
When the oxygen picked up in the lungs by the blood has traveled with it to the organs, he finds there two well-known friends—hydrogen and carbon.
You smile, and exclaim at once, "Then he marries them, does he?"
Yes, my dear child; and it is only for that purpose he enters our bodies at all. And this is why I could not make you understand the nature of respiration until I had explained that of fire to you. As I have told you before, it is the same thing. Invite air into your body by the bellows of your chest, or drive it into the fire by the kitchen bellows—it is always king Oxygen whom you are sending to his wedding.