232 POPULAR LECTURES AND ADDRESSES. 



known there as early as 2400 years before the 

 Christian era. 



The directive quality of the magnet, which 

 constitutes the essence of the mariner's compass, 

 was not known to the Greeks and Romans ; for in 

 the writings of Homer, Theophrastus, Plato, 

 Aristotle, Lucretius, and Pliny, we find abundant 

 evidence of knowledge of all the other ordinary 

 magnetic phenomena, but not a trace of any know- 

 ledge of this most marked property. It is clear that 

 of all those writers, or of the observers and experi- 

 menters on whom they had depended for infor- 

 mation, not one had ever supported a piece of 

 loadstone, or of magnetized steel, in such a manner 

 as to leave it free to turn round horizontally : or 

 that if any one of them had ever done so, he was 

 remarkably deficient in perceptive faculty. 



The earliest trace we now have of the mariner's 

 compass in Europe is contained, according to 

 Professor Hansteen (Inquiries Concerning tJie 

 Magnetism of the Earth ), in an account of the 

 discovery of Iceland by the Norwegian historian 

 Ara Frode, who is cited as authority for the fol- 



