Levi Strauss did not invent jeans, but he is considered the first person to make and sell great numbers of them. He was born in Bavaria, an area that is part of Germany. In 1847 he and his family moved to the United States.

Levi Strauss opened a small dry goods store, first in New York, then in San Francisco, California. Among the products he sold were jeans. These pants were especially useful for miners in California. They needed clothing made from a strong material. Jeans are usually made from a heavy cotton cloth called denim.

Levi Strauss partnered with a clothing maker named Jacob Davis. Davis had invented a process for making rivets (铆钉) for jeans. These little metal connectors helped hold the pieces of cloth together to make the jeans stronger.

In 1875, the government gave Strauss and Davis a patent (专利) for their invention. That meant no one else could legally copy it without their permission. In 1928 the Levi Strauss company registered (注册) the word “Levi’s” as a trademark for their product.

The Smithsonian’s National Museum of American History in Washington has one of the oldest known pairs of Levi’s. Writer James Sullivan published a book called “Jeans: A Cultural History of an American Icon.” In the book, he says jeans show two American values, creativity and rebellion.

Cowboys wore jeans in the old Wild West. In the 1950s, people saw famous Hollywood actors like James Dean and Marlon Brando wearing jeans in movies.

Today jeans come in blue but also lots of other colors and in many styles and at all prices.

There are 195 countries in the world today and actually none of them have purple on their national flags. Throughout history, purple was never used to represent a kingdom.

So what’s wrong with purple? It’s such a popular color today. The answer is really quite simple. Purple was just far too expensive.

The color purple has been related to royal power and wealth for centuries. Queen Elizabeth I didn’t allow anyone except close members of the royal family to wear it. Purple’s unique position comes from the rarity and high cost of the dye used to produce it. The dye was from a small sea snail that was only found in the Tyre area of the Mediterranean. Over 10,000 snails were needed to create just one gram of Tyrian purple; not to mention lots of work went into producing the dye, which made purple dye so expensive even for some royal families. Third century Roman Emperor Aurelio famously wouldn’t allow his wife to buy a scarf made from purple silk because it cost three times its weight in gold. A single pound of dye cost three pounds of gold, which equals 56,000 dollars today. Therefore, even the richest countries couldn’t spend that much having purple on their flags.

In 1856, 18-year-old English chemist William Henry Perkin by accident created a man-made purple dye while attempting to produce an anti-malaria drug. He noticed that it could be used to dye cloth. He patented the dye and mass-produced it. Therefore everybody could afford it.

Till now, a handful of new national flags have been designed and a few of them have chosen to use purple.

Paper is one of the most important products ever invented by man. Wide spread use of written language would not have been possible without some cheap and practical material to write on. The invention of paper meant that more people could be educated because more books could be printed and distributed. Together with the printing press, paper provided an extremely important way to communicate knowledge.

How much paper do you use every year? Probably you cannot answer that question quickly. In 1900 the world's use of paper was about one kilogram for each person a year. Now some countries use as much as 50 kilograms of paper for each person a year. Countries like the United States, England and Sweden use more paper than other countries.

Paper, like many other things that we use today, was first made in China. In Egypt and the West, paper was not very commonly used before the year 1400. The Egyptians wrote on a kind of material made of a water plant. Europeans used parchment for many hundreds of years. Parchment was very strong; it was made from the skin of certain young animals. We have learnt of the most important facts of European history from records that were kept on parchment.