For thousands of years, people thought of glass as something beautiful to look at. Only recently have they come to think of it as something to look through. Stores display their goods in large glass windows. Glass bottles and jars that hold food and drink allow us to see the contents. Glass is used to make eyeglasses, microscopes, telescopes, and many other extremely useful and necessary objects. Until the Second World War, most of the glass used for optical  instruments was imported from Europe. However, during the war Americans could not get European glass, and they were forced to make their own. Therefore, new kinds of glasses were developed that had been previously unknown. These new effects were achieved by mixing other chemical elements with the sand. Some of these new glasses are very strong and can resist many kinds of shocks. Legend has it that a very hard glass was invented by a Roman who showed his discovery to the Emperor. When the Emperor saw the glass he feared that it would become more valuable than gold and sliver, making his treasure worthless. Therefore, he had the glassmaker killed, and the secret was not discovered again for hundreds of years. In the present century, safety glass was invented for use in modern cars and planes. Safety glass is made by placing a layer of plastic between two layers of plate glass. When the outside layer of glass is broken, the pieces do not scatter  and injure people. Some glass of the type is strong enough to resist bullets . Although nowadays plastics have replaced glass under conditions where glass might be easily broken, there are new uses being developed, for the greatest advantage of glass is that its component  parts are inexpensive and can be found all over the world. Why does the author tell us the legend?
To prove the Roman was the first inventor of hard glass. To support the Americans were as clever as the Romans. To give some information about hard glass. To provide a historical event concerned with hard glass.