Let us imagine that we are out on a piece of nearly level land, many, many times larger than our playground. Such a broad, nearly level stretch of land is called a plain.

If this plain were covered with rich green grass and beautiful flowers, we should call it a prairie. In the summer it is a vast sea of waving grass. On the prairie we might find herds of wild horses and cattle, which feed upon the rich grass. If it were late in the summer, when the grass is dry and crisp, it might catch fire, and we might then see a grand sight—a prairie on fire.

We now come to another plain, miles and miles long, miles and miles wide. No rain falls here, and therefore we see no grass, nor flowers, nor cattle, nor horses, nothing but dry, burning sand, rocks, or gravel. We are in a desert. But we are so thirsty and tired!

No water to drink, no shade from the burning sun! Suddenly, in the midst of the desert, we come to a beautiful grassy spot. There is a cluster of date-palm trees, and, better still, a well or a spring of fresh water. This pleasant spot in the desert is called an oasis. Here we may quench our thirst, and rest beneath the shade of the trees.

An oasis  is a fertile spot in a desert. What does fertile  mean? When do we say land is fertile? When barren? When desert?

Find a picture of a palm tree, and try to draw it.

If we were really in a desert, we might see a company of merchants carrying goods to sell in the countries they visit. Such a company is called a caravan. The goods are packed in bundles, which are carried on camels' backs. The camel can live for a long time without drinking, and can carry a heavy load of merchandise a long distance. It is sometimes called the ship of the desert.

Why do travelers use camels to cross the desert? Why do they not use horses? If you can not find answers to these questions in your books at home, ask your teacher about them.

You have seen a small whirlwind in the street. The leaves flew round and round, the dust whirled along in clouds. Trees are sometimes torn from the ground, and houses overturned, by a strong wind.

Now think of a wind-storm in the desert. A loud, rustling noise is heard. Great clouds of fine sand are lifted into the air—clouds which darken the sun! Travelers must at once jump from their camels, cover themselves with their cloaks, and lie flat on the ground.

The poor beasts will close their eyes and nostrils, and kneel with their backs to the wind until the storm has passed over.

Thankful will the travelers be if none of them are buried in the sand.