The second is a very slow, dull gas, called nitrogen; and nothing will burn in it at all. Pure oxygen would be too active for us to live in, so it is mixed with nitrogen.

When we breathe, breathe, the air goes down into our lungs, which are something like sponges, inside our chests.

These sponges have in them an immense quantity of little blood vessels, and great numbers of little air vessels; so that the blood almost touches the air; there is only a very, very thin skin between them.

Through that skin, the blood sends away the waste and useless things it has collected from all parts of the body, and takes in the fresh oxygen which the body wants.

You have often heard man's life compared to a candle. I will show you some ways in which they are much alike.

When a candle or lamp burns, if we keep it from getting any new air, it soon uses all the lively gas, or oxygen, and then it goes out. This is easily shown by placing a glass jar over a lighted candle.

If the candle gets only a little fresh air, it burns dim and weak. If we get only a little fresh air, we are sickly and weak.

The candle makes another kind of gas. It is called carbonic acid gas, which is unhealthy and not fit for breathing. The heat of our bodies also makes this gas, and we throw it off in our breath.

Oxygen and carbon, in a separate condition, make up a good part of our flesh, blood, and bones; but when they are joined together, and make carbonic acid gas, they are of no further use to us.

You might go to a store and buy sand and sugar; but if they became mixed together as you brought them home, you would not be able to use either one of them, unless some clever fairy could pick them apart for you.

You see now one great way of spoiling the air. How are we to get to get rid of this bad air, and obtain fresh air, without being too cold?

In summer time this is quite simple, but in winter it is more difficult; because it is a very bad thing to be cold, and a thin, cold draught of air is especially bad.

The bad air loaded with carbonic acid gas, when we first breathe it out, is warm. Warm gases are much lighter than cold

The air is constantly moving about; rising and falling, sweeping this way or that way, and traveling from place to place.

Not only the little particles out of our breath, but anything that gives the air any smell, does it some harm. Even nice smells, like those of roses, are unhealthy, if shut up in a room for some time.

Dirty walls, ceilings, and floors give the air a musty, close smell; so do dirty clothes, muddy boots, cooking, and washing. Some of these ought not to be in the house at all; others remind us to open

dows wide.

our win

All the things I have been saying to you about pure air, apply still more to sick people than to healthy ones.

Directions for Reading.-Read the following sentences carefully, and avoid running the words together.

The good air can not get in at all.

We are apt to take it for granted.

It is sure to make them ill.

Point out three other places in the lesson where similar errors are likely to occur.

Language Lesson.-Add ment to each of the following words, and then give the meaning of the words so formed,

arrange

move

settle

encourage