In the United States there are a great many birds. Many of them live in the woods; others are found in the fields. Some are seen in the gardens, and a few are kept in our houses. The eagle builds her nest upon the highest rock, while the wren forms her snug and tiny nest in the way-side hedge. The swallow plasters her nest upon the gable of the house or under the eaves of the barn. Out in the wheat-field we hear the whistle of the quail. The noise of the ducks and geese comes to us from the pond. The birds of prey dart downward through the air. Everywhere we find the birds. In autumn the migratory birds leave us, but they return in the spring. Even in March we hear the call of the robin. At the same time the bold and saucy blue-jay pays us his first visit. One hears the sweet songs of the birds from May until October. Some of them remain with us during the winter. There are many things that birds can do. The swallows fly with the greatest ease. The ostrich runs rapidly. Swimming birds dive with much skill. The owl moves noiselessly through the night air. Birds of prey search out their victims with keen vision. Nearly all birds build skillfully made nests with their bills and feet. Some make them out of straw, and the little birds usually line them with wool. The large birds of prey build theirs from small sticks and twigs. For the most part they hatch the eggs with the warmth of the body. Many birds are highly valued on account of their eggs, while others are prized for their flesh and feathers. Still others charm us with their songs. LESSON XXV SLEEP Of all the wonderful things about us, sleep is one of the most wonderful. How it comes, why it comes, how it does its kind, helpful work, not even the wisest people are able to tell. We do not have much trouble in seeking it, it comes to us of itself. It takes us in its kindly arms, quiets and comforts us, repairs and refreshes us, and turns us out in the morning quite like new people. Sleep is necessary to life and health. We crave it as urgently as we do food or drink. In our waking hours, rest is obtained only at short intervals; the muscles, the nerves, and the brain are in full activity. Repair goes on every moment, whether we are awake or asleep; but during the waking hours the waste of the tissues is far ahead of the repair, while during sleep the repair exceeds the waste. Hence a need of rest which at regular intervals causes all parts of the bodily machinery to be run at their lowest rate. In other words, we are put to sleep. Sleep is more or less sound, according to circumstances. Fatigue, if not too great, aids it; idleness lessens it. Anxious thought, and pain, and even anticipated pleasure, may keep us awake. Hence we should not go to bed with the brain excited or too active. We should read some pleasant book, laugh, talk, sing, or take a brisk walk, or otherwise rest the brain for half an hour before going to bed.