T. C. Lethbridge in one of his books describes how birds can find each other when one is far away from the other. He believes that lines of force, or lines of life, stand round people, animals and even things like metals. These lines can be found with a pendulum——something heavy hanging on a long piece of silk or other material. The length of the silk is important. Each kind of thing needs a special length. An example may make this clear.

　　Suppose we want to find a piece of glass in a garden. We have to know the right length of the pendulum for glass. So we take the pendulum to a piece of glass, bringing nearer and nearer. It is moving from side to side, and so it will continue until we find the right length. We know now that this is 14 inches, for glass. If then, we let the length of the silk be 14 inches; the pendulum will stop moving from side to side when we bring it near to the glass. It will begin to ground in a kind of ring. (It will do this even if the glass is below the ground.) The “rate” for glass is therefore 14. Other rates are, for example, 22 for silver, 20 for diamonds, 29 for gold, 32 for iron, 20 for electricity, 24 for men and 29 for women. The pendulum stops moving from side to side because the lines of force near the thing have an effect on it.

　　So Mr. Lethbridge believes that there is an entirely different world around us and that it has lines of force in it. These are up-and-down lines, and they may reach the sun. They seem to go up (and down) forever. Mr. Lethbridge has found them with his pendulum in a room above the room in which the object is.

　　If there are lines of force like these, perhaps birds can sense them, or other lines like them. If so, this may in the future help to explain bird migration. But at present this science (If it is a science) is only beginning. Who knows what the future may hold?

　　1.Scientists fixed metal bands to a bird’s leg so as to learn something about its flying route.

　　2.The eighteen birds were let go soon after they had been brought to the island of Oahu.

　　3.In the experiment mentioned in paragraph four, the “days” were made longer and longer and this gave the birds an illusion that spring was approaching.

　　4.The turning of the earth directs the birds to their destinations.

　　5.According to the passage, some birds take a regular trip of 2,000 miles from Alaska to Hawaii. There is no land on their way, so they can find nothing over the blue waters to remember.

　　6.The ice in the South Pole does nothing to help a bird find its way.

　　7. Migrating birds fly up north again in the spring because of the overly dense population of different kinds of birds in the warm region.

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　　8.tells the birds when to fly south.

　　9.From the South Pole, the six birds sent by Mr. Robert Wood could go nowhere but .

　　10. T. C. Lethbridge maintains that can be found in all animals, and all metals.