Four great inventions of acient China(2)

Gunpowder

The prevailing academic consensus is that gunpowder was discovered in the 9th century by Chinese alchemists searching for an elixir of immortality By the time the Song Dynasty treatise, Wujing Zongyao , was written by Zeng Gongliang and Yang Weide in AD 1044, the various Chinese formulas for gunpowder held levels of nitrate in the range of 27% to 50%.[By the end of the 12th century, Chinese formulas of gunpowder had a level of nitrate capable of bursting through cast iron metal containers, in the form of the earliest hollow, gunpowder-filled grenade bombs.

In AD 1280, the bomb store of the large gunpowder arsenal at Weiyang accidentally caught fire, which produced such a massive explosion that a team of Chinese inspectors at the site a week later deduced that some 100 guards had been killed instantly, with wooden beams and pillars blown sky high and landing at a distance of over 10 li (~2 mi. or ~3.2 km) away from the explosion.
By the time of Jiao Yu and his Huolongjing in the mid 14th century, the explosive potential of gunpowder was perfected, as the level of nitrate in gunpowder formulas had risen to a range of 12% to 91%,with at least 6 different formulas in use that are considered to have maximum explosive potential for gunpowder.By that time, the Chinese had discovered how to create explosive cannonballs by packing their hollow shells with this nitrate-enhanced gunpowder.

Four great inventions of acient China (1)

Compass

The earliest reference to magnetism in Chinese literature is found in a 4th century BC book called Book of the Devil Valley Master "The lodestone makes iron come or it attracts itThe earliest reference to a magnetic device used as a "direction finder" is in a Song Dynasty book dated to AD 1040-44. Here there is a description of an iron "south-pointing fish" floating in a bowl of water, aligning itself to the south. The device is recommended as a means of orientation "in the obscurity of the night." However, the first suspended magnetic needle compass was written of by Shen Kuo in his book of AD 1088.
For most of Chinese history, the compass that remained in use was in the form of a magnetic needle floating in a bowl of water. According to Needham, the Chinese in the Song Dynasty and continuing Yuan Dynasty did make use of a dry compass, although this type never became as widely used in China as the wet compass.
The dry compass used in China was a dry suspension compass, a wooden frame crafted in the shape of a turtle hung upside down by a board, with the lodestone sealed in by wax, and if rotated, the needle at the tail would always point in the northern cardinal direction. Although the 14th century European compass-card in box frame and dry pivot needle was adopted in China after its use was taken by Japanese pirates in the 16th century (who had in turn learned of it from Europeans), the Chinese design of the suspended dry compass persisted in use well into the 18th century.