北師大版高中英語(yǔ)模塊7--Unit 20 New Frontiers 2

[00:01.56]Gunpowder [00:03.47]Gunpowder was invented by the Chinese [00:05.73]in the eighth century AD. [00:08.28]Early Chinese scientists discovered [00:10.64]that they could make an explosive substance [00:12.76]by mixing sulphur,charcoal and saltpeter. [00:16.76]Gunpowder was used in warfare [00:18.93]and led to the development of many different [00:21.00]kinds of weapons. [00:22.77]For example, rockets carrying an explosive [00:25.28]shell of gunpowder could be launched [00:27.98]at enemy soldiers from a bamboo tube. [00:32.08]The Compass [00:33.66]The ancient Chinese noticed [00:34.96]that certain kinds of metals, [00:36.95]like iron ore, usually aligned themselves [00:39.39]in a north to south position. [00:41.84]By the third century, [00:43.17]they had started making the first, [00:44.84]simple compassesby floating small pins [00:47.92]of magnetic metal in bowls of water. [00:50.74]By the eleventh century, [00:52.11]the Chinese were using sophisticated [00:54.05]compasses to navigate their ships at sea. [00:57.90]In the West magnetism was not discovered [01:00.42]until the fifteenth century. [01:02.65]Until this time, European sailors [01:04.83]were still navigating by the stars. [01:06.56]

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