四大发明 The Four Great Inventions
The Technique of Making Paper
A crude type of paper was used for writing on as early as in the Western Han Dynasty. It was made from plant fiber, and was rather rough. Cai Lun, a eunuch of the Eastern Han Dynasty, used tree bark, rags and old fishing nets as raw materials, and produced a smoother and more convenient type of paper. By the fourth century, paper had replaced bamboo slips and silk as the main material for writing on.
The Invention of the Compass
Natural magnets were used as crude compasses as early as in the Warring States Period. By the Song Dynasty, artificial magnets had been invented, whose magnetism was more stable than that of natural magnets. With such artificial magnets, compasses were developed and used for navigation, together with degree markings. This greatly stimulated maritime trade.
The Technique of Printing
Printing has played a very important role in the history of civilization. Woodblock printing was in use at the time of the Sui Dynasty. But it involved laborious and expensive processes.
Bi Sheng of the Northern Song Dynasty determined to improve the printing technique, and he invented moveable type. He carved characters in reverse on blocks of clay, and baked the blocks in a kiln. The slugs of type were pressed onto a coating of rosin, wax and paper ash spread on an iron tray, which was then heated and cooled to fix the slugs. If there was a wrong character, it could easily be replaced, and the tray, slugs and coating could be used over and over again.
In the Ming Dynasty, bronze type was invented, and later lead type was used.
Gunpowder and Firearms
Alchemists were the first people in ancient China to dabble in chemistry. In the search for "pills of immortality",it was found that a mixture of sulfur, saltpeter and charcoal could cause an explosion. This mixture was mainly used for making fireworks, until the Song Dynasty, when it began to be applied for military use. Fire arrows and bombs were made using gunpowder, and crude muskets were used with devastating effect against Mongolian invaders.