TERRESTRIAL MAGNETISM, ETC. 245 



Much confusion, and much of the difficulty now 

 felt by practical men in understanding the elements 

 of magnetism, has arisen through British instru- 

 ment-makers having persisted up to the present 

 day in this evil usage, notwithstanding Gilbert's 

 strong remonstrance against it two hundred years 

 ago. It is no doubt proper to mark on the fly-card 

 of the compass the letters N. and S. at the points 

 which are directed towards the north and towards 

 the south, just as the letters E. and W. and N.E 

 and N.W. are marked on the card, to show the east 

 and west and north-east and north-west directions ; 

 and thus no confusion can arise as to the indica- 

 tions of the mariner's compass. But when a needle 

 or a bar of steel has letters N. and S. marked on its 

 ends to show its magnetism, N. ought to show true 

 North magnetism and S. true South. 



Gilbert gave his discovery of Terrestrial 

 Magnetism to the world in a Latin quarto volume 

 of 240 pages, printed in London in the year 1600, 

 three years before his death. A second edition ap- 

 peared at Stettin twenty-eight years later, edited by 

 Lochman, and embellished with a curious title-page 



