pole stars to tell directions on open ocean or new area before the discovery of the compass. When the weather was gloomy or severe, traveling was difficult. A lodestone compass was used in China during the Han dynasty between the 2nd century BC and 1st century AD, where it was called the "south-governor" (sīnán ). The earliest reference to a magnetic device used for navigation is in a Song dynasty book dated to 1040–1044, where 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." The first suspended magnetic needle compass was written of by Shen Kuo in his book of 1088. According to Needham, the Chinese in the Song dynasty and continuing Yuan dynasty did make use of a dry 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. People could readily locate a direction when sailing on large oceans and exploring new area with the creation of the round compass, which led to the discovery of the New World and the development of sailing ships. Gunpowder Originally, gunpowder was used to make fireworks for festivals and major events. It was later utilized as an explosive substance in cannons, fire-arrows, and other military weapons. During the Song and Yuan dynasties (960–1368), gunpower was in high demand due to numerous battles and the development of mass industry. Gunpowder was invented in the 9th century by Chinese alchemists searching for an elixir of immortality. By the time the Song dynasty treatise, Wujing Zongyao (武经总要), was written by Zeng Gongliang and Yang Weide in 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