part 9

98 Changes in the heat which comes to the earth from the sun are one cause of changes in the weather. This discovery is new. A man of science made the discovery in 1944. He made it by measuring the heat which comes to the earth every day from the sun. The amount of heat is different from day to day. On some days the sun sends more heat to the earth. On other days it sends less heat to the earth. There is more water in this glass than in that. We are making new discoveries every day. Columbus made the discovery of America in 1492. Columbus came to America in his ship in 1492.

99 What were some other great discoveries? One of them was fire. Fire is of very great use to us. It gives us heat. Another great discovery was the wheel. Wheels are round. They go round. A cart. They are of very great use to us. Another great discovery was clothing. What are these? These are some other sorts of clothing. The making of cloth was a great discovery. This is how we make cloth. These are threads. (See page 47.) They go across from one side to the other of a frame.

100 These are other threads. They go across the first threads. They go under and over them. This is cloth. This is a roll of cloth. We make clothing of cloth. We make cloth of threads. We make threads from wool and cotton and silk. We get wool from sheep. Wool is the thick warm hair of sheep. We take the wool off the sheep's back with scissors.

101 We make threads from the wool by twisting the hairs round and round. That wheel is going round. It is giving a twist to the thread. It is twisting the thread. We get cotton from the cotton plant. Cotton is the soft white hair round the seeds of the plant. These are different sorts of seeds. Plants come up from seeds which come from other plants of the same sort. We get silk from the silkworm. This worm makes a soft strong thread of silk and puts it round itself like a coat.

102 Wool, cotton, and silk are different sorts of cloth. We make clothing of all these sorts of cloth. When the weather is cold we put on thick warm wool clothing. When the weather is warm we put on thin cotton clothing. Cotton clothing is not as warm as wool clothing. Thick clothing keeps us warm. It keeps us warmer than thin clothing. Thick cloth keeps air in it, between the threads. The air does not let heat go through it. A thick roof keeps the heat of the house in. A thin roof lets the heat go through it. A thick roof keeps the heat of the sun out.

103 Here is a pencil. It is straight. It is not bent. Here is a glass of water. I put the pencil in the water. The pencil seems bent where it goes into the water. The pencil is straight but it seems bent. It seems like this. But it is like this. It is straight, not bent. It seems bent, not straight.