LESSON XVII.
The same subject, continued.
Mother. Did you ever see a person rub his hands together, when he was cold?
Daughter. O yes, mother, a great many times. I have seen father come in from the cold, and rub his hands together, and afterwards hold them to the fire and rub them again, and then they get warm.
Mother. And now, Caroline, take your hand and rub it quickly backwards and forwards, over that woolen table-cloth, on the table in the corner of the room, and tell me whether that will make your hand warm.
Daughter. O, yes, dear mother; I feel it grow warmer, the faster I rub it.
Mother. Here are two small pieces of wood. Touch them to your cheek, and tell me whether they feel warm now.
Daughter. They do not feel warm, nor cold, mother.
Mother. Now rub them together quickly a little while, and then touch them to your cheek.
Daughter. O, dear, mother! they are so hot that they almost burnt my cheek.
Mother. Yes, Caroline; and do you not recollect, when you read Robinson Crusoe, that his man Friday made a fire by rubbing two pieces of wood together?
Daughter. O, yes, dear mother; and I have often wondered why Alice could not light her lire and the lamp in the same manner, without those matches, which have so offensive a smell.
Mother. It is very hard work, my dear, to obtain fire by rubbing two pieces of wood together; and it would take too long a time to do it. The two pieces of wood would grow warm by a very little rubbing; but in order to make them take fire, they must be rubbed together a great while.
Daughter. But, mother, if it takes so long a time to get fire by rubbing two pieces of wood together, why can Alice set the match on fire so easily by rubbing it once on the sand-paper?
Mother. That is what I am about to explain to you, my dear. Here, take this piece of paper and hold it up to the lamp.
Daughter. It has taken fire, mother.
Mother. Now take this piece of pine wood, and hold that up to the lamp in the same manner, and see whether that will take fire too.
Daughter. Yes, mother, it has taken fire; but I had to hold it up to the lamp much longer than I did the paper.
Mother. Now take this piece of hard wood, and do the same with that.
Daughter. The hard wood takes longer still to catch fire, mother.
Mother. Yes, my child. And now I am going to make the hard wood take fire more quickly than the paper did.
Daughter. Dear mother, how can you do it?
Mother. I am going to show you, my dear. Here is a small phial, which contains something that looks like water. It is spirits of turpentine. I shall dip the point of the piece of hard wood into the phial, and take up a little of the spirits of turpentine. Now, Caroline, touch the point of the hard wood with the turpentine on it to the flame.
Daughter. Why, mother, it caught fire as soon as I touched the flame with it!
Mother. Yes, certainly; and you now see that some things, like the spirits of turpentine and the paper, take fire very readily, and others take fire with more difficulty.
Daughter. Yes, mother; but when Alice drew the match across the sand-paper, there was no flame nor fire to touch it to. How, then, could it take fire?
Mother. Hold this piece of paper up to the blaze of the lamp, my dear, but be careful not to touch the fire or flame of the lamp; only hold it close to the blaze.
Daughter. Why, mother, it has taken fire!
Mother. You see, then, that a thing will sometimes take fire when it does not touch the fire.
Daughter. Yes, mother; but I do not understand where the fire comes from.
Mother. The fire comes from the heat, my dear. Now, you know that heat is produced by rubbing two things together; and that some things, like the spirits of turpentine, take fire very easily, or with very little heat; and others, like the hard wood, require to be heated some time,—or, in other words, require much heat,—to make them take fire, or to burn. Some things require only as much heat to make them take fire as can be obtained by rubbing them together very quickly, like the wood which Robinson Crusoe's man Friday used.
Daughter. But, mother, the match is made of wood,—why does that take fire so easily?
Mother. It is true, Caroline, that the match is made of wood; but it has something at the end of it, which takes fire much more easily than the spirits of turpentine. Indeed, so easily does it take fire, that it requires only so much heat to set it on fire as can be obtained by drawing the match once across the sand-paper.
Daughter. But, mother, matches do not always take fire. I have seen Alice rub several across the sand-paper, before she could set one on fire.
Mother. That is true, and the reason of this is, that the matches are not all well made. Now, if I should take several pieces of hard wood and tie them together, and dip their ends into the spirits of turpentine, what would happen, if the ends of some of the pieces did not touch the spirits of turpentine, because I had not tied them together with their points all even?
Daughter. Why, mother, some of them would take fire easily, because the points had the spirits of turpentine on them; while those which did not touch the spirits could not be lighted so easily.
Mother. So it is, my dear, with the matches. They are all dipped into the substance which takes fire so easily; but some of the ends do not reach the substance, and do not become coated with it, and therefore they will not light more easily than the pine wood of which they are made.
