TERRESTRIAL MAGNETISM, ETC. 243 



Physician in ordinary to Queen Elizabeth, dis- 

 covered the true explanation of the wonderful 

 directional tendency manifested by magnetized 

 needles. His explanation is, that the earth, not 

 the pole-star, or any other " lode-star," but the earth, 

 acts upon a movable needle, as does a lump of 

 lode-stone or a bar magnet, held anywhere in its 

 neighbourhood. To illustrate Gilbert's discovery 

 I described a simple mode of experimenting, by 

 which any one sufficiently interested may find for 

 himself the mutual influence between two magnets, 

 and suggested a mode of supporting the needle by 

 flotation, to give it mobility, as this was interesting 

 in connection with the earliest known European 

 account of the mariner's compass, that of Guiot of 

 Provence, which describes the needle as being 

 floated on a straw in a basin of water. If a sewing 

 needle be hung by a fine thread tied round its 

 middle, it will have freedom of motion enough to 

 let any one verify for himself, without the trouble 

 of floating it, that two needles similarly magnetized 

 by the use of a little toy magnet (bar or horse-shoe), 

 act upon one another with repulsion between ends 



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