Here's a selection of festivals for tourists to the United States in summer.

    San Francisco Silent Film Festival

    Films at this odd cinematic event have a variety of musical accompaniments,including piano and violin.It includes some classic silent movies.If you want to see them all,you can buy a festival pass.

    May 29 to June 1; www.silentfilm.org

    Union Street Festival

    This popular street fair stretches out over six blocks of the city,in the fashionable shopping area of Union Street.This year,there's beer,wine tasting and more separate themes—fashion,cuisine,tech,local,craft,and health and fitness.

    June 7 to 10; www.unionstreefestival.com 

    North Beach Festival

    This is San Francisco's oldest street party,with live entertainment,delicious food and arts and crafts.Situated in the Little Italy district,known for its associations with the "Beat Generation",festival goers are guaranteed plenty of good Italian food.There is also as the “blessing of the animals”,a San Francisco tradition which takes place at the National Shrine of Saint Francis of Assisi (610 Vallejo Street) at 2 pm on both days of the festival.

    June 14 to 16; www.sfnorthbeach.org

    Stern Grove Festival

    This is the oldest free summer arts festival of its kind in the United States.It includes a wide variety of acts,from the local symphony orchestra to well known artists such as Smokey Robinson.

    Sundays from June 22 to Aug 24; www.sterngrove.org

    Earthquakes are something that people fear. There are some places that have few or no earthquakes. Most places in the world, however, have them regularly (有规律地). Countries that have a lot of earthquakes are usually quite mountainous.

    The earthquake which was talked about most in the United States was in San Francisco in 1906. Over 700 people died in it. The strongest one in North America was in 1964. It happened in Alaska.

    Strong earthquakes are not always the ones that kill the most people. In 1755, one of the strongest earthquakes ever recorded was felt in Portugal. Around 2,000 people died.

    In 1923, a very strong earthquake hit Tokyo, the Yokohama area of Japan. One hundred and forty thousand people died. Most of them died in fires which followed the earthquake.

    One of the worst earthquakes ever was in China in 1976. It killed a large number of people. The worst earthquake ever recorded was also in China, in which about 80,000 people were killed or injured. This earthquake happened in 2008.

    Earthquakes worry people a lot. The reason is that we often do not know when they are coming. People cannot prepare for them.

    Have you ever heard of the Coral Sea? It is home to an amazing variety of turtles, sharks, whales, dolphins, large fish, birds, corals, plants, and many other species. Many of these species are endangered elsewhere in the world, but still survive in the healthy environment of the Coral Sea.

    The Coral Sea is a large series of coral reefs located off the northeast coast of Australia. This area is three times larger than Australia's famous Great Barrier Reef, which the Coral Sea borders.

    The Coral Sea is one of the few coral reef environments that have remained largely undamaged by over-fishing, oil and gas exploration and pollution. However, statistics show that coral reefs around the world are disappearing five times faster than rainforests. It is very likely that in the near future the Coral Sea will face the same threats to its existence.

    The Australian government is currently looking at options for protecting the Coral Sea but has made no decisions. Environmentalists are pushing for laws to declare the Coral Sea area a marine protected area, which will mean a large “no-take zone” for fishermen, a no-exploration zone for gas and oil companies and a no-dump zone for pollution, possibly making the Coral Sea a marine park larger than any other in the world.

    We can write letters to Australian leaders, Australian environmental protection agencies, and Australian friends, to let them know that people worldwide support this protection of the Coral Sea. To lose this last great marine wilderness world would be a loss for the whole world.

    These days, tall modern buildings are everywhere. But if you want to see how life was back in the old days, China still has many beautiful water towns to visit. And now, CNN has chosen five of the country's most beautiful ones.

    The village of Zhouzhuang in Jiangsu calls itself the “oldest water town in China”. The village was built in 1086and is crossed with canals. Taking a boat ride through town, the red lanterns might make you think of China's romantic past.

Hongcun in Anhui is 900 years old. It was built to look like a big ox. Huangshan Mountain is the head; the town is the body and the bridges are legs. Hongcun is filled with lakes and beautiful Anhui-style buildings.

    Fenghuang in Hunan doesn't look like a bird, but its name means “phoenix” in Chinese. The town is really as beautiful as the mythical bird. The stilted buildings on each side of the Tuojiang River make the area look like a scene from a postcard.

    Huangyao in Guangxi is known for its natural fengshui. The town lies in a river bend. People say it can prevent the villagers' good fortune from flowing away

    While most water towns are in the south, Shangdong's Tai'erzhuang stands out in the north. The town lies on the bank of the Beijing-Hangzhou Grand Canal. It was a busy trading center during the Ming and Qing dynasties. In the town, there are ancient bridges, a canal and temples, making you think of its past glory.

    Larger brain size linked to longer life in deer. The size of a female animals' brain may determine whether they live longer and have more healthy later generations, according to new research led by the University of Cambridge.

    The study, published in the Royal Society Open Science journal, shows that female red deer with larger brains live longer and have more surviving later generations than those with smaller brains. Brain size is heritable and is passed down through the generations. This is the first extensive study of individual differences in brain size in wild mammals and draws on data comparing seven generations of deer.

    Across species of mammals, brain size varies widely. This is thought to be a consequence of specific differences in the benefits and costs of a larger brain. Mammals with larger brains may, for example, have greater abilities that enable them to adapt better to environmental changes or they may have longer lifespans. But there may also be disadvantages: for instance, larger brains require more energy, so individuals that possess them may show reduced ability to give birth to young babies.

    The researchers, based at the University of Cambridge's Zoology Department and Edinburgh University's Institute of Evolutionary Biology, wanted to test if they could find more direct genetic or non-genetic evidence of the costs and benefits of large brain size by comparing the longevity(长寿) and survival of individuals of the same species with different sized brains. Using the skulls of 1,314 wild red deer whose life histories and breeding success had been monitored in the course of a long-term study on the Isle of Rum, they found that females with larger endocranial volumes(脑腔容量) lived longer and produced more surviving offspring in the course of their lives.

    Lead author Dr Corina Logan, a Gates Cambridge Scholar, says, "The reasons for the association between brain size and longevity are not known, but other studies have suggested that larger brains are a consequence of the longer-lived species having longer developmental periods in which the brain can grow. These predictions were generated from cross-species correlations; however, testing such hypotheses requires investigations at the within-species level, which is what we did. "

    Dr Logan adds, "We found that some of the cross-species predictions about brain size held for female red deer, and that none of the predictions were supported in male red deer. This indicates that each sex likely experiences its own set of trade-offs(权衡,协调) with regard to brain size. "The study also showed that females' relative endocranial volume is smaller than that of males, despite evidence of selection for larger brains in females.

    Professor Tim Clutton Brock, who set up the Rum Red Deer study with Fiona Guinness in 1972 and started the work on brain size, points out, "The reason that this kind of study has not been conducted before is that it requires long term records of a large number of individuals across multiple generations and data of this kind are still rare in wild animals."

    The world we live in gets more mechanized every year. Some countries which were mainly agricultural a hundred years ago have now become industrial. New factories and towns have been built on good agricultural land. There are now fewer farms to serve a much greater population, so these farms must be more efficient in order to produce as much food as possible. There is no place in the modern agricultural world for the inefficient farmer. Unfortunately, many of the picturesque aspects of farming are disappearing in the search for efficiency. The more tractors are used, the fewer horses are needed. Everyone agrees that horses are far more pleasant to look at than tractors. But they are less efficient. Cows are usually milked by machinery nowadays, and even pigs are fed automatically. There is not much art or poetry on the modern farm, and the old traditional idea of a farm as a slow, peaceful, romantic place is totally wrong nowadays.

    The modern farmer has to be a mechanic, a scientist, an accountant and a gambler. The more mechanized farming becomes, the more expert the farmer has to be. He must understand what machinery is necessary for his kind of farm, and he must know how to use it efficiently. He must also understand the new technical advances in agriculture, and how to use chemical and synthetic products to improve his crops. The more workers a farmer employs, the more he must know about the problems of wages and taxes. As in any other industry, most modern farmers find it necessary to employ office staff to deal with these. But although he has more modern equipments and far more scientific aids than his grandfather had, the farmer is still dependent upon the weather. As he can never be sure what the weather will do, he must be prepared to take risks, and face the possibility of losing everything.