Scientists are debating how to limit their newly-discovered power to change genetic structure (结构). Scientists already modify the genes (基因) of farm animals and agricultural plants to make them more productive or stronger. But now they can also change genes in wild animals and plants. These genes would continue into later generations. For example, it may be possible for scientists to remove from existence the kind of mosquitoes, small flying insects, that carry the Zika virus. They might also be able to permanently remove species (物种) of plants and animals that are damaging to other species.

    In a report published last week, the U. S. National Academies of Sciences, Engineering and Medicine (NAS) said it supports continued research on this kind of gene control. But it warned that it is not possible to know what will happen when these changed plants and animals are released (释放) into the wild.

    Sixteen biologists, ethicists (伦理学家) and policymakers are on an NAS committee that is examining the issue. They say that there is value to the new technology. But, they say, there is not enough evidence to support the release of modified organisms (生物体) from the laboratory into nature.

    Many people would support stopping mosquitoes and rats from carrying diseases. But scientists say we must understand the possible scientific, ethical, legal and social results of such action before we decide whether to take it. Gene modification is spread through reproduction (繁殖).

    Changed genes will continue to spread as long as an animal or plant continues to reproduce. They cannot be limited to a farm or kept within a country's borders. Scientists are wondering what may happen if a modified organism mates with another species. They are not yet sure how the modified genes would affect the other species. It is possible that those genes could harm those creatures or even lead to their disappearance from our planet.

    We do not know when man first began to use salt, but we do know that it has been used in many different ways throughout history. Historical evidence shows, for example, that people who lived over 3,000 years ago ate salted fish. Thousands of years ago in Egypt, salt was used to preserve (保存) the dead.

    Stealing salt was considered a major crime (罪行) during some periods of history. In the eighteenth century, for example, if a person was caught stealing salt, he could be put in prison and his ears could be cut off.

    In the Roman Empire, one of the most important roads was the one that carried salt from the salt mines to Rome. Guards were stationed(安置) along the route to protect against salt thieves, and they received their pay in salt, thus bringing the English word, salary. Any guard who fell asleep while on duty was thought to be “not worth his salt”, and as a result he would get a little less salt on his next payday. The expression, “not worth his salt”, is still used today in English.

    In the modern world salt has many uses beyond the dining table. It is used in making glass and airplane parts, in the growing of crops, and in the killing of weeds (杂草). It is also used to make water soft, to melt (融化) ice on roads and highways, to make soap, and to fix colors in cloth.

    Salt can be got in various ways besides being taken from mines underground. Salt water from the ocean, salt water lakes or small seas can be used to make salt. Yet, no matter where it comes from, salt will continue to play an important role in the lives of people everywhere.

    One hot night last July, when our new baby wouldn't or couldn't sleep,I tried everything I could think of: a warm bottle,songs,gentle rocking.Nothing would settle him.Guessing that I had a long night ahead of me,I brought a portable TV into his room,figuring that watching the late movie was as good a way as any to kill the hours till dawn. To my surprise,as soon as the TV lit up,the baby quieted right down,his little eyes focused brightly on the tube.Not to waste an opportunity for sleep,I then tiptoes（踮着脚走）out of the room,leaving him to watch the actors celebrate John Bellushi's forty-fifth birthday.

    My wife and I heard none of the baby that night,and the next morning when I went into his room,I found that he was still watching TV himself.

    I found in my baby's behavior a symbol of the new generation.My wife and I had given him some books to examine,but he merely spit upon them.When we read to him,he did not feel comfortable.And so it is in the schools. We find that our students don't read and that they look down upon reading and scold those of us who teach it.All that they want to do is to watch TV.After this experience with the baby,however,I have come to a conclusion:"Let them watch it!"If television is that much more attractive to children than books,why should we fight about it?Let them watch it all that they want!

    Summer Science Class registration begins on March 8 ! If you are interested in science，the environment，or conservation and you are in grades 7 －12 ，sign up soon for Black Rock Forest Consortium's Summer Science Class program. You can download the Summer Science Classes 2013 brochure here. It is easy to register；just call 845-534-4517 or click here.

    Twelve-week-long courses in the natural sciences and the arts are offered at Black Rock Forest in Cornwall from July 15 through August 9.Two more classes are offered with site partners，including “The Art of Scientific Observation，” hosted jointly by Black Rock Forest Consortium and Storm King Art Center ，one of the world's leading sculpture parks ，and “A Nautical   Expedition” hosted jointly by the Consortium and the Constitution Marsh Audubon Center.

    We are delighted to announce two special “away” classes that are part of the Summer Science Class program this year: an“Adirondack Eco-Adventure” beginning August 11，and “Conservation Biology in Florida，” beginning June 23 and featuring field work on the Gulf Coast in cooperation with the University of Florida's Seahorse Key Marine Biological Laboratory. For more information on the Summer Science Class program，please read our press release. Black Rock Forest Consortium is a nonprofit organization founded in 1989 to advance scientific understanding of the natural world through research，education and conservation programs.

    Grandparents Answer a Call

    As a third-generation native of Brownsville, Texas, Mildred Garza never planned to move away. Even when her daughter and son asked her to move to San Antonio to help with their children, she politely refused. Only after a year of friendly discussion did Ms. Garza finally say yes. That was four years ago. Today all three generations regard the move as a success, giving them a closer relationship than they would have had in separate cities.

    No statistics show the number of grandparents like Garza who are moving closer to adult children and grandchildren. Yet there is evidence (证据) suggesting that the trend (趋势) is growing. Even President Obama's mother-in-law, Marian Robinson, has agreed to leave Chicago and move into the White House to help care for her granddaughters. According to a study by grandparents.com, 83 percent of the people said Mrs. Robinson's decision will influence grandparents in the American family. Two-thirds believe more families will follow the example of Obama's family.

    “In the 1960s we were all a little wild and couldn't get away from home far enough or fast enough to prove we could do it on our own,” says Christine Crosby, publisher of Grand, a magazine for grandparents. “We now realize how important family is and how important it is to be near them, especially when you're raising children.”

    Moving is not for everyone. Almost every grandparent wants to be with his or her grandchildren and is willing to make sacrifices (牺牲), but sometimes it is wiser to say no and visit frequently instead. Having your grandchildren far away is hard, especially knowing your adult child is struggling, but giving up the life you know may be harder.

    Even by the standards of poor countries, India is alarmingly — and unnecessarily — dirty. It needs to clean up. Most time of year, its capital, Delhi，smells as if something is burning. That is because of many things: the carcinogenic diesel（柴油）that supplies three quarters of the city's motor fuel, the dirty coal that supplies most of its power, the rice stalks that nearby farmers want to clear after the harvest and so on. All these make Delhi's air the most poisonous of any big city.

    This does not just make life unpleasant for a lot of Indians. It kills them. Recent estimates put the annual death toll from breathing PM 2.5 alone at 1.2—2.2 million a year. The lifespan of Delhi residents is shortened by more than ten years, says the University of Chicago-Consumption of dirty water directly causes 200,000 deaths a year, a government think-tank estimates, without measuring its contribution to slower killers such as kidney disease. Some 600 million Indians, nearly half the country, live in areas where clean water is in short supply. As pollutants taint groundwater, and global warming makes the vital monsoon（季风）rains more abnormal, the country is poisoning its own future.

    Indian pollution is a danger to the rest of the world, too. Widespread dumping of antibiotics（抗生素）in rivers has made the country a hotspot for anti-microbial（抗微生物）resistance. Emissions of carbon dioxide, the most common greenhouse gas, grew by 6% a year between 2000 and 2016, compared with 1.3% a year for the world as a whole.

    In the past India has explained its failure to clean up its act by pleading poverty, noting that richer countries were once just as dirty and that its output of waste per person still lags far behind theirs. But India is notably grubby（肮脏的）not just in absolute terms, but also relative to its level of development And it is becoming grubbier.

    It is true that some ways of cutting pollution are expensive. But there are also cheap solutions，such as undoing mistakes that Indian bureaucrats（官僚）have themselves made. By funding rice farmers, for instance, the government has in effect cheered on the overusing of groundwater and the burning of stalks. Rules that encourage the use of coal have not made India more self-reliant, as intended, but instead have led to big imports of foreign coal while blackening India's skies. Much cleaner gas-fired power plants, meanwhile, sit idle.

    Reliant on big business for funding and on the poor for votes, politicians have long ignored middle-class complaints about pollution, failing to give officials the backing to enforce rules. That is a pity, because when India does apply itself to ambitious goals, it often achieves them

    Next year it will send its second rocket to the Moon.

    Narendra Modi, the prime minister, promised with admirable frankness when he took over to rid the country of open defecation（缺陷）. Four and a half years and some $9 billion later, his Clean India campaign claims to have sponsored the building of an astonishing 90 million toilets. This is impressive, but India is still not clean. Its skies, its streets, its rivers and coasts will remain dangerously dirty until they receive similar attention.