中国古代四大发明怎么说？(2)

The invention of gunpowder had a close relationship with the advanced ancient workmanship of smelting industry. People began to know a lot of chemistry knowledge about the nature of different mineral materials during the process of smelting operation. With the knowledge, ancient necromancers tried to seek the elixir of immortality from certain kinds of ores and fuel. Although they failed to get what they were looking for, they discovered that an explosive mixture could be produced by combining sulfur, charcoal, and saltpeter （potassium nitrate）. This mixture finally led to the invention of gunpowder although its exact date of invention still remains unknown.

Many historical materials indicate that gunpowder first appeared before the Tang Dynasty （618-907）. From 300 to 650AD several recipes were written about inflammable mixtures. Some historians date the invention of gunpowder at 850AD when a Taoist book warned of three specific elixir formulas as too dangerous to experiment.

The military applications of gunpowder began in the Tang Dynasty. Explosive bombs filled with gunpowder and fired from catapults were used in wars. During the Song and Yuan dynasties （960-1368）, the military applications of gunpowder became common and some other weapons like "fire cannon", "rocket", "missile" and "fireball" were introduced.

In the Yuan Dynasty （1279-1368）, the method of powder-making was introduced to the Arab world and Europe, bringing a series of revolutions to weapon manufacturing, as well as to stratagem and tactics on the battlefield. From Italy the making of gunpowder soon spread to other European countries, and by the 1350s it had become an effective weapon on the battlefield