Weather has a strong effect(影响) on people. It influences health, intelligence (智力) and feelings. In August, it is very hot and wet in the southern part of the United States. People there easily have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is hot at some times and very cold at other times. People in those states will have heart trouble after the weather changes in February or March.
      The weather can also influence intelligence. For example, in a 1983 study by scientists, the IQ scores of some college students were very high during storm, but after the storm, their scores were low. Storms can increase intelligence. Very hot weather, on the other hand, can decrease(减少) it. Students in many schools of the United States often do badly in exams in the hot months of the year(July and August).
      Weather also has a strong effect on people's feeling. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel depressed during cold weather. In hot summer weather, on the other hand, fat people may feel unhappy. At about 65F, people become stronger.
      Low air pressure(气压) makes people feel free, but it also increases forgetful- ness. People leave more bags and umbrellas on buses and in stores on low pressure days. There is a“perfect weather”for work and health. People feel best at a tempera- ture of about 64F with 65 percent humidity(湿度).
      Are you feeling sick, sad, tired, forgetful, or very intelligent today? The weather may be the reason.

    In 1826, a Frenchman named Niepce needed pictures for his business .But he was not a good artist .So he invented a very simple camera. He put it in a window of his house and took a picture of his garden .That was the first photo.

    The next important date in the history of photography was in 1837. That year, Daguerre, another Frenchman, took a picture of his reading room .He used a new kind of camera in a different way. In his picture you could see everything very clearly, even the smallest thing. This kind of photo was called a Daguerreotype.

    Soon, other people began to use Daguerre's way. Travelers brought back wonderful photos from all around the world .people took picture of famous buildings, cities and mountains.

    In about 1840, photography was improved .Then photographers could take pictures of people and moving things .That was not simple .The photographers had to carry a lot of films and other machines. But this did not stop them, for example, some in the United States worked so hard. Mathew Brady was a famous American photographer. He took many pictures of great people .The pictures were unusual because they were very lifelike.

    Photographers also became one kind of art by the end of the 19th century. Some photos were not just copies of the real world .They showed feelings like other kinds of art.

    If you travel by air across the center of Africa or South America, you fly over forests for thousands of kilometres．These great forests are the seas of trees．They are full of thousands and thousands of different kinds of plants and animals．However, the world's forests are getting smaller all the time．We are cutting down the trees because we need wood, and we need more farmland as well．Some people say that there will not be any forests like these left in 20 to 30 years．What will happen if they disappear? If we cut down our forests, a lot of plants and animals will disappear from the world, in a lot of places the new farmland will soon look like the old deserts, for example, crops will not grow there．What's worse, it will not rain very often, and the weather will get very hot．Perhaps the climate of the world will change, which will be dangerous for everyone in the world．That is why we must take care of our forests．