Magnetic declination described by Shen Kuo

What was discovered

Shen Kuo describes needles magnetised by rubbing with lodestone, compares ways of suspending them, and notes that they do not point exactly south but deviate slightly to the east. It is the first written mention of magnetic declination.

In Europe declination was recognised in the 15th century and measured systematically in the 16th.

What it led to

• navigation with a suspended magnetised needle
• correction for declination in geomancy and navigation

Built on

• Thermoremanent magnetisation (south-pointing fish)1044
• Lodestone spoon compass (Si Nan)

Made possible

• Magnetic navigational compassc. 1100
• First isogonic chart (Halley's magnetic variation chart)1701

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