7. Make up a story of Franklin's kite experiment using the following sentences and sentences of your own (our sentences are given in a disorderly way):

1. The key was connected to the lower end of the string, 2. The story about Franklin's famous kite is known all over the world. 3. They took some necessary things such as: a kite with a long string, a key and so on. 4. It was proved that lightning is a discharge of electricity. 5. It was a stormy day. 6. The electricity was conducted from the clouds down the string to the key. 7. The kite was flying high among the clouds. 8. The rain wetted the string. 9. Atmospheric electricity greatly interested Franklin. 10. The rain fell.

8. Define what parts of speech these words are:

application, ability, continuous, use, important, numer­ous, civilization, electric, familiar, reader, widely, useful, powerful, property, certainly

9. Form sentences with each of the following words: similar, simple, single, magnetic, orderly, practical, scientific.

10. Use the following expressions in sentences of your own:

all over the world; as well as; in this connection; in the form of; needless to say; to pay attention to

11. Speak on magnetism.

12. Compare:

1. A generator and a motor.

2. Potential power and kinetic power.

3. Chemical power and mechanical power.

4. Nuclear power station and steam power station.

LESSON SEVEN

THE EARLY HISTORY OF ELECTRICITY

History shows us that at least 2,500 years ago or so, the Greeks were already familiar with the strange force (as it seemed to them) which is known today as electricity. General­ly speaking, three phenomena made up all of man's knowledge of electrical effects. The first phenomenon under consideration was the familiar lightning flash - a dangerous power, as it seemed to him, which could both kill people and burn or destroy their houses. The second manifestation of electricity he was more or less familiar with was the following: he sometimes found in the earth a strange yellow stone which looked like glass. On being rubbed, that strange yellow stone, that is to say, amber, obtained the ability of attracting light objects of a small size. The third phenomenon was connected with the so-called electric fish which possessed the property of giving more or less strong electric shocks. It was known that in some parts of the world such shocks could be obtained by a person coming into contact with the electric fish.

These three effects could be observed by the man of 25 centuries ago and the same three effects, and no more, made up all the knowledge of electrical phenomena for the man liv­ing about four centuries ago. Nobody knew, of course, that the facts observed were due to electricity. People could neither understand their observations nor find any practical appli­cations for them.

As a matter of fact, all of man's knowledge in the field of electricity has been obtained during the last 370 years or so. Needless to say, it took a long time before scientists learned how to make use of electricity. In effect, most of the electrically operated devices, such as the electric lamp, the refrigerator, the tram, the lift, the radio, and so on, are less than one hundred years old. In spite of their having been employed for such a short period of time, they play a most important part in man's everyday life all over the world. In fact, we cannot do without them at present.

No scientists have been mentioned who contributed to the scientific research on electricity as centuries passed. However, famous names are connected with its history and among them we find that of Phales, the Greek philosopher. As early as about 600 B.C. (that is, before our era) he discov­ered that when amber was rubbed it attracted and held minute light objects. However, he could not know that amber was charged with electricity owing to the process of rubbing.

For more than 20 centuries people were familiar with the above-mentioned phenomenon before anything was done to find out more about it. Then Gilbert, the English physicist, began the first systematic scientific research on electrical phenomena. He discovered that various other substances possessed the property similar to that of amber or, in other words, they generated electricity when they were rubbed.

He gave the name "electricity" to the phenomenon he was studying. He got this word from the Greek "electrum" meaning amber, "electrum," in its turn, meaning "sun." The name was certainly given amber because of its yellow color.

Many learned men of Europe began to use the new word "electricity'" in their conversation and were soon engaged in research of their own. Scientists of Russia, France and Italy made their contributions as well as the Englishmen and the Germans.