_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.

LESSON XVIII.

_The same subject, concluded._

_Daughter._ Well, mother, I understand, now, how the match is set on fire. It is rubbed on the sand-paper, and that produces heat, and the heat sets the match on fire. But I always thought that fire makes heat, and not that heat makes fire.

_Mother._ Heat does not always make fire, Caroline; for, if it did, everything would be on fire.

_Daughter._ Everything on fire, mother! why, what do you mean?

_Mother._ I mean, my dear, that everything contains heat.

_Daughter._ Everything contains heat, mother, did you say? Why, then, is not everything warm? Some things, mother, are very cold; as ice, and snow, and that marble slab.

_Mother._ Yes, my child, everything contains heat, as I shall presently show you. When Alice goes to make a fire in a cold day, she does not carry the heat with her, and put it into the fire, nor into the wood, nor the coal, does she?

_Daughter._ Why, no, to be sure not, mother.

_Mother._ And the heat that comes from the fire, after it is made, does not come in at the windows, nor down the chimney, does it?

_Daughter._ Why, no, mother; it feels cold at the windows, and cold air comes down the chimney.

_Mother._ But, after the fire is made, we feel much heat coming from the fire, do we not?

_Daughter._ Why, yes, mother; that is what the fire is made for. We feel cold, and we want a fire to make us warm; and when the fire is made, it sends out heat, and makes us warm.

_Mother._ Well, now, where can the heat come from? You know what fire is made from, do you not?

_Daughter._ Certainly, mother; the fire is made of wood, or of coal.

_Mother._ But is the wood or the coal warm before the fire is made?

_Daughter._ No, mother, the wood and the coal come from the cold wood-house, or the cellar, and they are both very cold.

_Mother._ And yet, the wood and the coal become very hot when they are on fire.

_Daughter._ O yes, mother, so hot that we cannot touch them with our hands, and we have to take the shovel or the tongs to move them.

_Mother._ And do they burn the shovel and the tongs, my dear?

_Daughter._ Why, no, mother; if they did, the shovel and the tongs would be of little use in stirring the fire.

_Mother._ Can you think of any reason why they do not burn the shovel and the tongs?

_Daughter._ You told me, mother, that some things require a very little heat to set them on fire, and that other things require a great deal. I suppose that there was not heat enough to set them on fire; and if there had been, they would not burn, because they are made of iron.

_Mother._ You are partly right, my dear, and partly wrong. They would not burn, because there was not heat enough in the fire to burn them.

But there are very few things, and in fact it may be doubted whether there is anything, which will not burn, when sufficient heat is applied.

But let us return to the fire: you say the heat does not come from the windows nor from the chimney, and you say, also, that the wood and the coal are both cold. Now, where can the heat come from?

_Daughter._ I am sure I cannot tell, mother; will you please to tell me?

_Mother._ You recollect that I told you that the rubbing of the match on the sand-paper produces a little heat, which caused the match to burn.

The match was then applied to the shavings, and, as it was burning, gave out heat enough to set the shavings on fire; the shavings produced heat enough to set the pine wood, or kindling, on fire, and then the pine wood, or kindling, produced more heat, and set the wood and coal on fire. Now, there was nothing to produce the heat but the match, the shavings, the wood and the coal; and _the heat must have been in them_.

The fire only served to set it free, and let it come out of the match, the wood, and the coal.

_Daughter._ But, mother, how did the heat get into the wood and coal?

_Mother._ It is not known, my dear, how the heat _got into_ the wood and coal, any more than how the fruit gets on to a tree. We say that it grows on the tree; but what growing is, and how it is caused, are among the secrets of G.o.d.