题目内容
We all know that it is possible for ordinary people to make their homes on the equator (赤道), although often they may feel uncomfortably hot there. Millions do it. But as for the North Pole (北极)—— we know that it is not only a dangerously cold place, but that people like you and I would find it quite impossible to live there. At the present time only the scientists and explorers can do so, and they use special equipment. Men have been travelling across and around the e-quator on wheels, on their feet or in ships for thousands of years; but only a few men, with great difficulty and in very recent time, have ever crossed the ice to the North Pole. So it may surprise you to learn that, when traveling by air, it is really safer to fly over the North Pole than over the e-quator. Of course, it is not true about landings in the polar region, but the weather, if we are fly-ing at a height of 5,000 meters above the Pole is a delight. At 4,000 meters and move above the earth you can always be sure that you will not see a cloud in the sky as far as your eyes can reach.In the tropics ( 热带), on the other hand, you are not certain to keep clear of bad weather even at such heights as 18,000 or 20,000 meters.Aeroplanes can’ t climb as high or as quickly in cold air as in warm. Nor can clouds. In practice, this is an advantage to the aeroplane, which is already at a good height when it reaches the polar region and so does not to climb, while at the same time cold air keeps the clouds down low. The polar region is
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Trees are useful to man in three important ways: they provide him with wood and other prod-ucts; they give him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important. In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without ,them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious:for where there are trees, their roots break up soil--allowing the rain to sink in--and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When all the top-soil is gone, nothing remains but worthless desert.Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation. Why does land become desert after all trees are cut down
Trees are useful to man in three important ways: they provide him with wood and other prod-ucts; they give him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important. In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without ,them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious:for where there are trees, their roots break up soil--allowing the rain to sink in--and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When all the top-soil is gone, nothing remains but worthless desert.Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation. Why do forests in many parts of the world slowly disappear
Trees are useful to man in three important ways: they provide him with wood and other prod-ucts; they give him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important. In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without ,them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious:for where there are trees, their roots break up soil--allowing the rain to sink in--and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When all the top-soil is gone, nothing remains but worthless desert.Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation. Why did the country mentioned in the passage suffer from floods and starvation
Trees are useful to man in three important ways: they provide him with wood and other prod-ucts; they give him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important. In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without ,them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious:for where there are trees, their roots break up soil--allowing the rain to sink in--and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When all the top-soil is gone, nothing remains but worthless desert.Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation. What does the author tell us in this passage
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