In 1086 Chinese scholar and scientist of the Song Dynasty Shen Kuo (Shen Gua) wrote Dream Pool Essays while virtually isolated on his lavish garden estate near modern-day Zhenjiang, in the southwest of Jiangsu province.
Dream Pool Essays contained the earliest description of the principle of the compass—magnetizing a needle by rubbing its tip with lodestone, hanging the magnetic needle with one single strain of silk with a bit of wax attached to the center of the needle. Shen Kua pointed out that the needle prepared this way sometimes points south, sometimes points north.
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