T". ( -^'O ) 



LETTER TO BARON A. DE HUMBOLDT, ON THE 

 INVENTION OF THE MARINER'S COMPASS. 



Sir, 



' In a letter dated Potsdam, the 4th of January, 1834, you did me 

 the honour to ask information of me as to the period when the 

 Chinese became acquainted with the polarity of the needle, and of 

 their application of it to the compass. I had already, long before, 

 collected several passages and notes on this subject, but they were 

 insufficient to elucidate the question, and I should not, perhaps, yet 

 have thought of arranging and completing them, had not this occasion 

 of complying with your request presented itself. It will thus, if I be 

 not deceived, have turned to the benefit of science ; for, in seeking 

 an answer to your request, I have been fortunate enough to meet in 

 several Chinese books with facts which, from their number and im- 

 portance, enable me trace a nearly complete history of the invention 

 of the magnetic needle in China. 



These facts I have now the honour to transmit to you, accompanying 

 them by a few observations relative to the antiquity of the knowledge of 

 the loadstone in Asia and in Europe. I add the nomenclature of 

 the epithets by which this extraordinary stone is known, as well as 

 that of the magnetic' needle, in the various idioms and dialects of 

 both these quarters of the globe. I should consider myself fortunate 

 vi'ere this undertaking to contribute to illuminate a point so curious 

 in the history of human civilisation, and were it to present any interest 

 to that portion of the learned world more particularly accustomed, 

 wherever it reads your name, to find remarkable discoveries or 

 interesting observations. 



I must first assert it to be established that the ancients were 

 ignorant of the polarity of the loadstone, although it appears that 

 they had some vague notions of its property of attracting iron on one 

 side, and repelling it on the other. If, indeed, the Greeks and Romans 

 had really been acquainted with this polarity, there is no doubt that 

 it would have been mentioned by them, and the silence of Claudian 

 on this subject, who has left us some good lines on the loadstone, 

 would be inexplicable. 



If Claudian had in the least suspected the polarity of the loadstone, 

 he would certainly not have failed to turn it to account in his allusion 

 to the imperturbability of the amorous passion he says exists between 

 this stone and iron. IBut neither with him, nor with any other writer 

 of classical antiquity, do we find a single word that may give suspicion 

 of an acquaintance with the direction of the loadstone towards the 

 pole. Several of the learned have discussed ex-profcsso the progress 

 of navigation amongst the ancients, and have collected all the 

 passages of Greek and Roman writers having the least affinity to the 

 marine ; but these industrious persons have vainly sought amongst 

 all these evidences, a single line giving rise to the conjecture that 

 the ancients had any acquaintance with the polarity of the loadstone, 

 or of the magnetic needle, and still less with the utility of this latter 



