By the mid-nineteenth century, the term “icebox” had entered the American language, but ice was still only beginning to affect the diet of ordinary citizens in the United States. The ice trade grew with the growth of cities. Ice was used in hotels, pubs, and hospitals, and by some forward-looking city dealers in fresh meat, fresh fish, and butler. After the Civil War (1861-1865), as ice was used to refrigerate freight cars(货车), it also came into household use. Even before 1880, half the ice sold in New York, Philadelphia, and Baltimore, and one-third of that sold in Boston and Chicago, went to families for their own use. This had become possible because a new household convenience, the icebox, a precursor（前身）of the modem refrigerator, had been invented.

    Making an efficient icebox was not as easy as we might now suppose. In the early nineteenth century, the knowledge of the physics of heat, which was essential to a science of refrigeration, was undeveloped. The common belief that the best icebox was one that prevented the ice from melting was of course mistaken, for it was the melting of the ice that performed the cooling. Nevertheless, early efforts to economize ice included wrapping the ice in blankets, which kept the ice from doing its job. Not until near the end of the nineteenth century did inventors achieve the delicate balance of insulation(绝缘) and circulation needed for an efficient icebox.

    But as early as 1803, an intelligent Maryland farmer, Thomas Moore, had been on the right track. He owned a farm about twenty miles outside the city of Washington, for which the village of Georgetown was the market center. When he used an icebox of his own design to transport his butter to market, he found that customers would pass up the rapidly melting butter of his competitors to pay an extra price for his butter, still fresh and hard in neat, one-pound bricks. One advantage of his icebox, Moore explained, was that fanners would no longer have to travel to market at night in order to keep their produce cool.

    Most students, when asked about their best graduation(毕业) gift, would probably reply, “ A car”, or “Money for a house”. Cai Kaiyuan, 21, made a difference choice. As a graduation gift to himself, he decided to work as a volunteer teacher in a distant village in Tibet.

    Cai, a student at Huan Railway Professional Technology College, at first planned to cycle from Sichuan to Tibet. It turned out cycling on a plateau(高原) was quite difficult. And it has kept changing his opinion on life. Cai's hands even became painful while cycling up a 5008-meter-high mountain, where temperatures often dropped to 18 below zero. At night, the ice covered the road and he fell off his bike three times. Little oxygen made him feel sick and weak. “At the most serious moment, I felt that was on the line,” said Cai.

    However, he also gained something unexpected. At Ya' an, a city in Sichuan, he met a group of tourists who are also university students. A girl called Wu Ling told him that she planned to work as a in a primary school in Tibet after her journey. He was impressed by the idea as she looked weak.

    It was not until he reached a family-run hotel in Shigatse that Cai's spirits began to rise. The hotel manager's two daughters enjoyed talking with him. The kids asked about his experiences on his trip, and showed him the beautiful local lakes. “They told me that they always liked to talk to guests, as they wanted to improve their Mandarin,” he said, “Their parents and many locals can only speak Tibetan.”

    Cai was moved by the girls' story. Their situation is worse and the local people have little chance to learn Mandarin because the schools are short of teacher. “1 want to do something to improve the situation for kids like them,” said Cai. His parents finally gave their agreement and his teachers also supported him.

    When Iwas.in the third grade, we had a hunt at school. We gathered up chalk，pencils，stones, and so on, rapidly filling our checklists. It was a very close race. I was out of breath when I reached the clover (三叶草)patch in search of the last, most hard-to-find item: a four-leaf clover.

    I was pretty sure that I was going to win. 1 have always been able to find four-leaf clovers. I just see them.

    I spent my childhood collecting and pressing four-leaf clovers into books at my mother's house. I started with big cloth- and leather-bound books. When I ran out of romantically bound volumes, I began to put my treasures into anything I could find: fiction paperbacks, cookbooks. The same is true in my house today. Shake a book, and a papery treasure just might fall into your hand.

    A few years ago, in Nova Scotia, my husband and I pulled off the road for a picnic. The ground was thick with clover. Some shoots had four, five, even six leaves. I lined them up on the picnic table to admire as my husband, never yet having found one four-leaf clover, looked on with awe. To me, it was simple. The differences in their shapes popped out, breaking the pretty pattern of the conventional clovers with their three perfect leaves.

    Two summers back, while waiting for an airport shuttle in Munich, I found a tiny four-leaf clover in a traffic circle and put it into my passport. On the way home, my husband and I were upgraded to business class. Friends attributed our good luck to the clover. I think, it's more likely that we were upgraded because a kind customer service officer took pity on us.

    People disagree about whether the luck lies in the finding or in the possession of a clover. Some believe that the luck is lost if the four-leaf clover is even shown to somebody else, while others think the luck doubles if it is given away. I believe that positivity is increased by sharing. I feel lucky to find the clovers so often, but I don't think they influence my life any more than it does to share anything a little special—that momentary closeness between you and a friend or a stranger, as you all lean in to wonder at a rare find.

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    Donald was not very good at math. He could not understand the teacher's explanations. Even when the teacher explained something a second time, Donald still could not understand it. "Never mind," Donald told himself, "I'm quite good at other subjects. I'll cheat in the math exam, and then I won't be in trouble."

    "I will sit next to the boy who's good at math,'' he thought, "and copy down his answers." The day of the exam came, and Donald sat next to Brian Smith, who was always at the top of the class in math. Donald carefully copied Brian's answers onto his own exam paper. At the end of the exam, the teacher collected the papers and graded them. Then she said, "Well, boys and girls. I've decided to give a prize to the student who got the highest grade. However, it's difficult for me to decide who to give the prize to, because two students, Donald and Brian, got the same grade."

    "Let them share it,'' one of the other students said.

    "I have thought about that,'' the teacher said, "but I have decided to give the prize to Brian." Donald was angry when he heard this. He stood up and said, "That is not fair. I got the same grade as Brian." "That is true," the teacher said. "However, Brian's answer to Question 18 was 'I don't know', while yours was 'Neither do I'."

    Traditional Chinese Medicine (TCM) needs to prove its worth through rigorous clinical trials, according to the head of one of China's largest herbal remedy companies, as a contentious new law to boost the $40bn sector comes into effect.

    Traditional Chinese Medicine is estimated by analysts to account for a third of sales in China's $117bn pharmaceutical (药学) market, the world's second largest. But most of those sales are of relatively cheap over-the-counter drugs, with many Chinese hospital doctors unwilling to prescribe TCM remedies because of the lack of evidence for their effectiveness.

    China's first law promising equal status for TCM and western medicine in the country's state-dominated healthcare system comes into effect this weekend. Provisions include encouragement for hospitals to set up TCM centres, and a licensing system for practitioners (从业者). "This law is very important for securing the status of TCM," said Wu Yiling, chairman of Yiling Pharmaceutical, a company that makes herbal remedies based on traditional recipes in the northern province of Hebei.

    Listed in Shenzhen, Wu Yiling has a market capitalization of RMB 20.7bn ($3bn). Mr Wu, the son of a herbal practitioner, controls a family fortune of $1.6bn, according to the Hurun Rich List.

    Mr Wu is both a supporter of the nature of Qi—the mystical energy force that provides the basis for much of TCM theory—and the clinical trials vital to western pharmaceutical companies. "TCM needs to develop using modern research methods," he said.

    For instance, researchers from Peking and Cardiff Universities tested the health benefits of Yiling's herbal medicine Yangzheng Xiaoji, publishing papers in the International Journal of Oncology that showed the drug can slow the growth of cancer tumours. "The theory and recipe is TCM, but in practice the evaluation of our medicines is carried out according to western evidence-based methods," Mr Wu said.

    Analysts say such tests can help gain support from doubtful hospital doctors and boost prescriptions. "Doctors need strong evidence that drugs definitely work," said Serena Shao, healthcare analyst at brokerage CLSA. "Some of these companies are currently doing clinical trials, and getting proof that their drugs have the same efficacy (功效) as chemical drugs. That's the way to go." she added.

    The TCM law has been greeted with doubt from China's western-schooled medical establishment, which points to a lack of rigorous training for TCM doctors, and a recent series of shocking events involving herbal injections believed to have been harmful. "Officials will try and encourage TCM, but also will be very cautious about what kinds of TCM they use in hospitals," added Ms Shao.