If a diver surfaces too quickly, he may suffer the bends. Nitrogen (氮) dissolved (溶解) in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles (气泡) accumulate in a joint, is sharp pain and a bent body—thus the name. If the bubbles form in his lungs or his brain, the consequence can be death.

    Other air-breathing animals also suffer this decompression (减压) sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs. That these ancient sea animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil (化石) bones that have caved in on themselves are thus a sign that the animal once had the bends.

    Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaur bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world's natural-history museums, looking at hundreds of ichthyosaurs from the Triassic period and from the later Jurassic and Cretaceous periods.

    When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before they died, but not a single Triassic specimen (标本) showed evidence of that sort of injury.

    If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly—and, most strangely, they lost it afterwards. But that is not what Dr Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.

    Whales that suffer the bends often do so because they have surfaced to escape a predator (捕食动物) such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey (猎物) as well as predator—and often had to make a speedy exit as a result.

    This day three foreign gentlemen came to a bus stop in England and waited. About five minutes later, the bus they wanted came along. They were just going to get on when suddenly there was a loud noise behind them. People rushed onto the bus and tried to push them out of the way. Someone shouted at them. The bus conductor came rushing down the stairs to see what the trouble was about. The three foreigners seemed all at sea and looked embarrassed. No one had told them about the British custom of lining up for a bus — the first person who arrives at the bus stop is the first person to get on the bus.

    Learning the language of a country isn't enough. If you want to have a pleasant visit, find out as much as possible about the manners and customs of your host country. You will probably be surprised just how different they can be from your own. A visitor to India would do well if he/she knows that people there consider it impolite to use the left hand for passing food at table. The left hand is supposed to be used for washing yourself. Also in India, you might see a man shaking his head to show that he doesn't agree. But in many parts of India a shake of the head means agreement. Nodding your head when you are given a drink in Bulgaria will probably leave you thirsty.

    At a meal in countries on the Arabic Peninsula, you will find that your glass is repeatedly refilled as soon as you drink up. If you think that you have had enough, you should take the cup or glass in your hand and give it a little shake from side to side or place your hand over the top.

    In Europe it is quite usual to cross your legs when you are sitting talking to someone even at an important meeting. Doing this in Thailand, however, could cause trouble. Also, you should try to avoid touching the head of an adult — it's just not done in Thailand.

    Sitting on the peaceful coast of Galapagos Islands. Ecuador, watching the sun move quietly into the sea, you shouldn't forget that Charles Darwin (1809-1882) arrived here in 1835. He stayed on the islands for five weeks, observing various animals. This finally inspired (启发) his famous work, On the Origin of Species. You can certainly follow Darwin's footsteps and enjoy a trip from four to seven days to the islands. The islands are certainly a paradise (天堂) for wildlife, as there are no natural killers on the islands and the number of boats and visitors is under government control. Though you cannot walk freely as Darwin did about 200 years ago, each day is as impressive as it could be. The most well-known animal of the Galapagos is the giant tortoise(巨型海龟), which can be seen moving slowly around the highlands of Sanra Cruz, the second largest island in the archipelago(群岛). Some of these creatures are so old that they might have been seen in their youth by Darwin himself. Despite strict control over activities and timing, your stay on the Galapagos will be remembered as a chain of incomparable pictures: diving with sea lions that swim and play within inches of you; feeling small sharks touch your feet as you swim; and, most magically, seeing a whale and her baby surface with a great breath of air. Travelling between the islands and observing the wildlife that so inspired Darwin, you will feel as though you are getting a special view of an untouched world. At night you will sleep on board the ship, leaving the wildlife in complete occupation of the islands, which are as undisturbed now as they have been since the beginning of time.

    In one of the old buildings near our school, one could see an old man sitting by a large window on the first floor. His name was James. During the three years at school, I had hardly ever found him missing from his usual position.

    He was a high-ranking government official and lived happily with his wife. Once there was a bus accident, in which a number of passengers were seriously injured and were taken to the hospital for treatment. James was responsible for the rescue operation. It was a big hospital, but James was shocked to notice how ill-equipped it was. There were no enough life-saving drugs and life—supporting equipment.  The injured and their companions had to struggle there. James attempted to help. However, though he emptied his pockets, many of them died that day.

    That was a turning point in his life. He made a decision to devote his life to helping others, particularly the poor and needy patients and their companions. He began spending much of his income on these people. Since this required a lot of time and energy, he found it difficult to fulfill(履行) his official duties and therefore chose to retire, which, in turn, reduced his income considerably.

    His wife was deeply worried. Most of the time, James was out and paid least attention to home affairs. Meanwhile, as he was spending a lot helping others, she had to struggle even to meet the household expenses. Though she was not opposed to his helping the poor, she urged him not to overlook his own life and home, but it had no effect on him. One day they had a heated argument and in the end she left him, never to return. Though he continued with his work, this was a great blow and did serious harm to his health and enthusiasm and was soon forced to stay indoors. That was when he took his position by the window, spending his time looking outside.

    A few weeks after my graduation, I returned to school, only to find the buildings gone. I heard that they were torn down. All the people left except James. He refused to go and the next morning, he was found at his usual place by the window, dead.

    As global temperatures rise, trees around the world are experiencing longer growing seasons, sometimes as much as three extra weeks a year. All that time helps trees grow faster. For the past 100 years, trees have been experiencing fast growth in temperate regions from Maryland to Finland, to Central Europe, where the growth rate of some trees has even sped up nearly 77% since 1870. Assuming wood is just as strong today, those gains would mean more timber(木材) for building, burning, and storing carbon captured from the atmosphere. But is wood really as dense as it used to be?

    Hans Pretzsch, a forest scientist at the Technical University of Munich in Germany, and his colleagues wanted to find an answer. They carried out a study of the forests of Central Europe. They started with 41 experimental plots in southern Germany, some of which have been continuously monitored since 1870. Pretzsch and his team took core samples from the trees—which included Norway spruce, sessile oak, European beech, and Scots pine—and analyzed the tree rings using a high-frequency probe.

    They found that in all four species, wood density has decreased by 8% to 12%, they report online in Forest Ecology and Management. “We expected a trend of the wood density like this, but not such a strong and significant decrease,” Pretzsch says. Increasing temperatures, and the faster growth they spur, probably account for some of the drop. Another factor, Pretzsch says, is more nitrogen in the soil from agricultural fertilizer(化肥) and vehicle exhaust. Previous studies have linked increased fertilizer use to decreased wood density. Above all, the study suggests that the higher temperatures—combined with pollution from auto exhaust and farms—are making wood weaker, resulting in trees that break more easily and wood that is less durable.

    “I am getting worried,” says Richard Houghton, an ecologist at the Woods Hole Research Center in Falmouth, Massachusetts, who was not part of the new study. As the density of the samples dropped, so did their carbon content, by about 50%. That means forests may suffer more damage from storms and may be less efficient at soaking up the greenhouse gas carbon dioxide (CO2) than scientists had thought, Houghton says.

    Every year from March to October, Christian Moullec, also known as "Birdman," takes to the skies aboard his adapted light aircraft. However, the 58-year-old Frenchman's daily 30-minute flight is not just to enjoy the impressive views, but to guide flocks (鸟群) of lesser white-fronted geese (小白额雁) through safe migration paths which the birds can teach future generations.

    His deed began in 1995 when he noticed their declining population in the wilds of Lapland, Sweden. To prevent their numbers from dropping further, Moullec tried to get the threatened species to follow him along migration routes that would protect them from bird hunters.

    However, getting grown geese to follow his lead proved challenging. As young geese imitate and follow whomever they view as their parent, Moullec decided to raise the geese from birth.

    To help raise funds and awareness of his job to protect not just the geese but birds worldwide, Moullec often allows paying tourists to join him on the 30-minute-long flights aboard his aircraft. In addition to the trained birds flying alongside them, visitors, who come from as far as a 15-hour plane flight away, are treated to a variety of crane and geese species as well as breathtaking views of castles and cities.

    He often brings his camera along for the flights, capturing photos not just for their beauty, but for what they describe. Moullec believes the use of agricultural chemicals has done harm to wild European birds, with more than a third disappearing in the last 30 years. "It's a disaster," he said. "My beautiful images with flying birds should be used to tell this story."