7、Careful and careless are different as fire and water. But it is strange that quite a few scientists have both these qualities. They are both careful and careless. Newton（牛顿）, the famous English scientist, was such a person.
Once Newton invited a friend to dinner at home. When they were ready to eat, Newton left to get a bottle of wine. But after his friend had waited for a long time, Newton still didn't come back. At last his friend found Newton in his lab. When Newton was going to get the bottle of wine, he suddenly had a new idea for his experiment. So he quite forgot his friend and the dinner. Another time, Newton was leading a horse up a mountain, and held the rein（缰绳）in his hand. While he was walking, he kept thinking about problems. When he got to the top of the mountain, he found that the rein was not in his hand and that the horse was gone.
Einstein（爱因斯坦）was another example. Once he was waiting for a friend at a bridge. While waiting, he became lost in thought. It started to rain. The rain kept on for some time. When he took out a piece of paper to write something down, the paper was wet and then he knew that it was raining. But after he put the paper into his pocket, he forgot he was standing in the rain again.