Unit 3 Inventors and inventions Section Ⅰ Warming Up &；Reading-Pre-reading“That one looks just like a sheep！ And look over there. That one looks like a horse ！” Do you remember lying on your back in a grassy field on a summer afternoon， discovering the soft shapes in the clouds in the sky？ Those were the good old days when you could see anything and everything in the clouds.,But now people look at the sky and see clouds in the shape of a motor company's advertising logo 标识， or a message inviting them to go out and buy a certain brand 品牌 of beer. These cloud pictures are not products of their imaginations. Instead ， they are produced by a machine. These new floating advertisements are called Flogos ； the name stands for “floating logos.” They're made from a mixture of soapy foam 泡沫 and a lighterthanair gas such as helium，and they can be made into different sizes and shapes depending on the advertisement.,Flogos can last up to an hour if weather conditions are good， and they can fly several kilometers high. Advertisers can rent a Flogo machine for $2，500 a day. The setup is normally performed within 1 to 2 hours， and it will release four Flogos per minute. Advertisers can fill the air with any shape or message they want.,Some people are worried that the Flogos might not be pollutionfree 无污染的. However， the Flogo's inventor insists that the soap he uses is natural， and that a Flogo just dissipates 消失 in the air， leaving nothing behind. Though it may be true that Flogos are environmentally friendly， some people believe that the natural clouds in our memory may be replaced by manmade ones. They are afraid that soon there wil...
