This gas is constantly breathed out from our lungs. It is the bad air that I told you about in Chapter XX., Part First, that leaves take from the lungs of animals, giving them back good air in return. You see, then, how important it is that this gas shall get from us to the leaves, and that the good gas from the leaves shall come freely into our lungs. But this can not be done unless there is a free circulation of the air. When people are shut up in a close room, a great deal of this bad gas is made in a little while, and unless it is let out of the room it does harm. It does not often kill any one at once, but it injures the health; and the poisonous effect repeated every day, though it be but a little, after a while may destroy life. A few persons are killed quickly by this gas made from burning charcoal; but a great many are killed slowly by it as it is given out from their lungs, because they do not take enough pains to let it escape.
Questions.—In what things is the gas that we burn like air? In what does it differ from air? What is said about the smell of gas? In what two ways is life sometimes destroyed by gas? What is flame in a common wood or coal fire? Tell about the blowing we sometimes see in wood on the fire. What is said about the making of gas? What is said about the gas that comes from burning charcoal? How are people sometimes killed by it? What is said about its being in wells? Tell about the Grotto of the Dogs. What is said about the lungs giving out this gas? How does it often do harm when given out in this way? Which kills the most people, the gas that comes from burning charcoal or that which comes from people’s lungs?
CHAPTER IX.
POWDER.
Powder is a very harmless thing of itself. You can take it into your hand and it will not hurt you; but touch it with fire, and it flashes and explodes; and if there is much of it, it breaks every thing in pieces all around it. When a magazine or a powder-mill blows up, there is great destruction of every thing that is near.
You know that powder is used in blasting rocks. A hole is drilled and the powder is put in. The blaster lights something which will burn very slowly down to the powder, so that he may have time to get out of the way. When the powder explodes, the rock is all broken apart into large and small pieces.
Powder produces its effects by changing into gas.
Now, how is it that the powder does all this? It does it by changing all at once into a great quantity of gas. That is all. When you look at some powder, a heap of black grains, there is no gas in it; but the moment that the fire touches it the powder is all gone. But how? Has it become nothing? No; it is changed into something else. The black powder is chiefly gas now. It is not all gas; if it were, you could not see it. The smoke that you see is gas, with something else from the burning powder mixed with it. This gas pushes out every way as soon as it is made, so that it may get room, and it does it so quickly that it carries every thing before it. It does the same that the air does when it moves very quickly, only it moves a great deal more quickly, and so does a great deal more.
Boy blasting a log.
This changing of powder into gas is done very quickly—as quick as a flash, as we say. I knew a boy that once forgot this in using some powder. He put some powder into a log of wood in order to split it; but, instead of fixing a slow match, as men do in blasting rocks, he touched off the powder, intending to get out of the way by running. But the powder was, of course, too quick for him. It blew him over, burning him a little, and frightening him a great deal.