Below is an account of the use of the magnetic compass for navigation from a book by Zhu Yu, son of a former port official and governor of Canton. The book is called Pingchow Table Talk and dates from 1117. Zhu writes:

According to the government regulations concerning sea-going ships, the larger ones can carry several hundred men and the small ones may have more than a hundred men on board. . . . The ship's pilots are acquainted with the configuration of the coasts: at night they steer by the stars, and in the day-time by the Sun. In dark weather they look at the south-pointing needle. They also use a line a hundred feet long with a hook at the end, which they let down to take samples of mud from the sea-bottom; by its appearance and smell they can determine their whereabouts.

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