Remember, when needful, the contempt of this Persian prince, my dear child; and let me beg of you, work for yourself. The dance of labor is worth quite as much as that of the ball-room, when you give your heart to it. It is even worth more, very often; and next time I will tell you why.
LETTER XXV.
CARBONIC ACID.
We are going to make acquaintance to-day with a new personage, who well deserves our attention. It is the child of oxygen and carbon, [Footnote: This is the name learned men have given to Charcoal.] though not in the same way that you are the child of your parents.
To tell you how it is made is more than I am able. It is a gas, or if you like the word better, it is an air; for when we say "gas," we mean "air;" only it is always a different sort of air from the air of the atmosphere, which learned people are not in the habit of calling gas. I cannot, therefore, show you carbonic acid itself, for it cannot be seen any more than the air which fills an empty glass. But I can tell you where there is some, and you even probably know it by its effects, although you have never heard its name.
Do you remember, on your aunt's wedding-day, that there was a sparkling wine called champagne, at the grand breakfast? You smile, so I conclude somebody gave you a little to taste; and if so, you will remember how sharp it felt to your tongue. Do you remember, too, how the cork flew out when they were opening the bottle, and how the noise of the "pop!" startled more little girls than one? It was carbonic acid which sent the cork flying in that wild way; the carbonic acid which was imprisoned in the bottle, in desperately close quarters with the wine, and which accordingly flew out, like a regular goblin, the moment the iron wire which held down the cork was removed. What sparkled in the glass, making that pretty white froth which phizzed so gently, as if inviting you to drink, was the carbonic acid in the wine, making its escape in thousands of tiny bubbles. What felt so sharp to your tongue was the same carbonic acid, in its quality of acidity, for thence it has its name; the word acid being borrowed from a Latin word signifying the sharp pungent taste, almost fine-pointed as it were, peculiar to all substances which we call acids.
It is carbonic acid also which causes the froth in beer and in new wine when bottled. It is he who makes soda-water sparkle and sting the tongue, and ginger-beer the same, if you happen to like it; and so far you have no particular reason for thinking ill of him. But beware. It is with him as with a good many others who have sparkling spirits, who make conversation effervesce with gayety, and who are very seductive in society when you have nothing else to do but to laugh over your glass, but whose society is fatal to the soul which delivers itself up to them. This charming carbonic acid is a mortal poison to any one who allows it to get into his lungs.
You remember what a violent headache your servant suffered from the other day after ironing all those clothes you had in the wash? She owed that headache entirely to this work which she did for you. She had remained too long standing over the coals over which her flat-irons were being heated. You know already that when charcoal burns, it is from the carbon uniting with the oxygen of the air; from this union proceeds that mischievous child, carbonic acid gas, in torrents, and the poor girl was ill, because she had breathed more of this than was good for her health. Observe well, that the room-door was open to let in the fresh air, and that there was a chimney, to allow the carbonic acid to escape. It was on this account that she got off with only a headache. Unhappily, there have sometimes been miserable people who, weary of life, and knowing this, but not knowing or thinking about the God who overrules every sorrow for good, have shut themselves up in a room with a brazier of burning charcoal, after taking the fatal precaution of stopping up every opening by which air could possibly get in; and when at last, in such a case, uneasy friends have forced open the well-closed door, they have found nothing within but a corpse. Then, too, there are those frightful accidents of which we hear so often, of workmen groping their way down into long disused wells, who have died as they reached the bottom; or of sudden deaths in coal-pits. In general these have been owing to the poor victims encountering the long pent-up carbonic acid gas, whose poisonous breath blasted and destroyed them at once.
You may well ask why I am telling you such horrible stories, and what I am coming to with my carbonic acid? But you have more to do with it than you think, dear child. You, and I, and everybody we meet, nay, and the very animals themselves, since their machines are of the same sort as ours, are all little manufactories of carbonic acid. The thing is quite clear. Since there is a charcoal fire lit in every part of our body, there always arises from the union of the oxygen brought by the blood with the carbon it meets in our organs, that mischievous child we have been talking about; and our throat is the chimney by which he gets away. He would kill us outright were he to stop in the house.
This is how it comes about: In proportion as the blood loses its oxygen, it picks up in exchange the carbonic acid produced by combustion, so that it is quite loaded with it by the time it returns to the lungs. There it takes in a fresh supply of oxygen, and discharges at the same time its overplus of carbonic acid, which is driven out of the body by the contractions of the chest, pell-mell with the air which has just been made use of in breathing. You are aware that this air is not the same at its exit as at its entrance to the body, and that if you try and breathe it over again it will no longer be of the same use to you. That is because it has lost part of its oxygen and brings back to you the carbonic acid which it had just carried off. If you take it in a third time, it will be still worse for you; and in case you should continue to persist—the oxygen always diminishing, and the carbonic acid always increasing in quantity—the air which was at first the means of your life will at last become the cause of your death. Try, as an experiment, to shut yourself up in a small trunk, where no fresh air can get in; or even in a narrow closely-shut closet, and you will soon tell me strange news. There will be no occasion to light a charcoal fire for you in there. Enough is kept burning in your own little stove, and you will poison yourself.