GASES.
[Sidenote: How the gas that we burn differs from air.]
I have told you about the air which we breathe, and which is all around
us; but there are other kinds of air. When we light the gas, what is it
that we set on fire? It is an air, or gas, as we call it, that comes
through the pipe to the burner. It is like the air which we breathe in
some respects. It is transparent; that is, you can see through it as
you can through common air. It moves about as easily as air does. But
it is different from the air in some things. It is lighter. The air has
no smell; but this gas has a very bad smell, as you may know when it
leaks out of the pipes. Air does not burn, but this gas does; and it is
curious that when it burns the bad smell is all gone.
Sometimes, when the gas leaks out of a pipe, it is very dangerous. If a
close room should get very full of it, and you should go into it with
a light, the gas in the room would all take fire and explode. Persons
have been killed in this way. It is well that the gas does smell badly,
for this lets us know when it leaks, so that we may guard against the
danger. We should let the gas out by opening doors and windows before
we bring a light in.
Persons have sometimes been killed by the gas in another way. You know
that there is in every gas-pipe something that you can turn so as to
shut the pipe, and thus keep the gas from coming out. Now persons
that do not know how the gas is managed have blown it out instead of
shutting it off. When this is done, the gas continues to come out
from the open pipe just as it did when it was burning, and gradually
fills the room; and if the person in the room goes to sleep, he will be
injured, and perhaps even killed by breathing the gas.
[Sidenote: Gas burning in a common fire.]
Did you ever think what flame is in a common wood or coal fire? It is
burning gas. The heat makes the gas out of the wood or coal, and this
takes fire just as the gas does that comes out of the burner when you
put a light to it. Sometimes you see a little stream of gas blowing out
of some part of a stick of wood, as gas blows out of a burner. It makes
quite a noise as it blows. If it is not on fire, you can set fire to it
just as you light the gas from a burner.
You see, then, that every fire-place, or grate, or stove is a gas
factory; but the gas is burned up as fast as it is made. The gas which
is made at the gas-works is made in such a way that it is not burned at
the time. It is made generally by heating coal, and is kept in large
reservoirs called gasometers. From them pipes branch out in the same
way that they do from water-works; and through these the gas goes all
about to different buildings, as water goes in aqueduct pipes; and as
the water comes out when you open the faucet, so does the gas when you
open the burner.
[Sidenote: Gas from burning charcoal.]
There is one gas that every one ought to know about, because many
persons have been killed by it from want of this knowledge. This gas
is made whenever charcoal is burned; and many deaths have occurred
from it by burning charcoal in small furnaces in close rooms. This is
often done to warm a room where there is no stove or fire-place. As the
charcoal burns slowly, the gas is made, and as it is heavier than air,
it spreads, at first, all over the floor. It gets higher and higher,
and at length reaches the mouths, of the persons in the room. If they
happen to be asleep, they are very apt to be killed by breathing the
gas; but if they are awake, they are conscious of the unpleasant
feelings the gas produces, and either go out into the air, or make some
noise which brings others to their relief.
[Sidenote: Gas sometimes in wells.]
This gas sometimes collects in wells, and kills men that go down into
them. Now there is one way by which we can always tell whether this gas
is in a well. If there be none there, we can lower a lighted candle
down to the water and it will not go out; but if there be any of this
gas there, the candle will go out as soon as it reaches it.
[Sidenote: The Grotto of the Dogs.]
There is in Italy a cave or grotto, which is called the Grotto of the
Dogs. The reason that this name was given to it will appear from what
I will tell you about it. This deadly gas is constantly made there in
some way that we do not understand. There is enough of it to reach
above a dog’s head, but it never gets up as high as a man’s head. While
a man, then, can breathe in the grotto perfectly well, a dog can not,
for he is down in the gas. A dog is kept there by some one living close
by, for the purpose of showing the effect on him to visitors. When he
is carried into the grotto, he soon falls down, and would die if he
were left there; but as they wish to keep him for exhibition to others,
they bring him out, and though he looks as if he were dead, dashing
some cold water on him and letting him breathe the fresh air soon
revive him.
[Sidenote: Gas breathed out from the lungs of animals.]
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?