Magnetic Declination in Mediaeval China

Abstract

THE traditional view that Christopher Columbus discovered magnetic declination on his first voyage to the West Indies in 1492 was put forward with great force by Bertelli¹ towards the end of the last century and has been repeated by many since. On the other hand, Crichton Mitchell², after having examined the evidence on which this claim was based, concluded that not only did Columbus not discover magnetic declination but that the existence of declination was known in Europe as early as 1450. In the past few decades, however, .the Columbus controversy has become irrelevant with the researches of Wang Chen-To³ and Needham⁴, who have shown that the credit for the discovery of declination must go to the Chinese. Needham, in particular, has tabulated eighteen recorded Chinese compass observations of declination covering the period about 720–1829. These are of interest not only to historians but also to geophysicists, for they represent the earliest recorded direct observations of the Earth's magnetic field. The question of their validity is therefore of great importance.