Can earthquake be predicted?

As scientists learn more about the causes of earthquakes, they become better able to predict them. First of all, they know that quakes are likely to occur in areas where the tectonic plates push against each other. They study these areas closely, using different instruments. They measure the vi­brations of the earth with seismographs, which record on rolls of paper all movements, both large and small. Scientists usually use the Richter scale, named after a famous seismologist, for these measurements. When an earthquake measures over 4.5 on the Richer scale, it is strong enough to cause damage. Scientists have determined that an area is not likely to have a large earthquake when many small quakes have been occurring. When the small quakes stop, then pressure builds and a strong quake is more likely.

There are several other ways to predict earthquakes. Scientists can measure the tiny changes in the tilt of the land that happen before earthquakes occur. Increases in the amount of radon, a sub­stance found in deep wells, as well as a higher level of water in the wells, can also mean that an earthquake is likely to occur. In addition, scientists have found that some animals, like dogs , be­have strangely before an earthquake : they become nervous and howl .

Seismologists have correctly predicted several earthquakes. In 1975, they said that an earthquake would occur in Liaoning Province, China, one month, and then one hour, before it hap­pened. In 1978, Russian scientists predicted an earthquake in the Altai mountains six hours before it occurred. However, not all earthquakes are predictable, and a system for predicting is not yet per­fected. Nothing on this earth is certain. Although people who live in California and Japan live with the possibility of a serious quake, perhaps the next strong earthquake will occur somewhere outside the "Ring of Fire".

TEXT #09

1. Read and translate the text

2. Vocabulary exercises

3. Grammar exercises

4. Speaking tasks

The discovery of the X-ray

Scientists working on a problem do not know and sometimes can't even guess what the final re­sult will be. Late on Friday, 8 November, 1895, Professor Rontgen, a German physicist, was doing an experiment in his laboratory when he noticed something extraordinary. He had covered an elec­tric bulb with black cardboard, and when he switched on the current he saw little dancing lights on his table. Now the bulb was completely covered; how then could any ray penetrate? On the table there were some pieces of paper which had been covered with metal salts. It was on this paper that the lights were shining. Professor Rontgen took a piece of this paper and held it at a distance from the lamp. Between it and the lamp he placed a variety of objects, a book, a pack of cards, a piece of wood and a door key. The ray penetrated every one of them except the key. He called his wife into the laboratory and asked her to hold her hand between the lamp and a photographic plate. She was very surprised by this request, but she held up her hand for a quarter of an hour, and when the plate was developed there was a picture of the bones of her hand and of the ring on one finger. The mysterious ray could pass through the flesh and not through the bone or the ring.

At a scientific meeting, Professor Rontgen called this new ray "the unknown", the X-ray. Doc­tors quickly saw how this could be used, and soon there were X-ray machines in all the big hospi­tals. The most obvious use for this discovery was to enable doctors to see exactly how a bone was fractured. Other uses came later. It was found that these rays could be used to destroy cancer cells, just as they destroyed the healthy cells of the doctors who first used the machines. Methods were found later by which ulcers in the stomach could be located, and the lungs could be X-rayed to show if there was any tuberculosis present.

TEXT #10

1. Read and translate the text

2. Vocabulary exercises

3. Grammar exercises

4. Speaking tasks