MAGNETIC APPARATUS. 



THE modern science of Magnetism may be said to date from the 

 publication, in the year 1600, of a treatise entitled, " De Magnete 

 magneticisque corporibus et magno magnete Tellure, Physio- 

 logia nova" (London, 4to), by William Gilbert, of Colchester, 

 physician. In this work it was for the first time clearly shown 

 that the earth, as a whole, has the properties of a magnet, and, 

 consequently, that the directive action exerted by it upon a 

 compass-needle represents only a special case of the mutual action 

 of two magnets. Before Gilbert's time some important contribu- 

 tions to the accurate observation of magnetic phenomena had 

 been made by George Hartmann, Vicar of S. Sebald's, Nuremberg,, 

 In a letter* to Duke Albert of Prussia, dated 4th March, 1544, 

 Hartmann describes some magnetic experiments that he had 

 shown in the previous year to King Ferdinand of Bohemia, 

 brother of Charles V., from which it appears that he was 

 acquainted with magnetic repulsion as well as attraction, and 

 knew that like poles repel, while unlike poles attract, each other ; 

 also that he had observed, contrary to the general belief of the 

 time, that, when one end of a compass-needle is stroked with a 

 pole of given kind, it acquires a polarity opposite to that of the 

 pole employed; and further, that he not only knew that the 

 variation of the compass was different in different places, but that 



* Printed in extract by Moser (Dove's Repertorium der Physik) vol. ii. 

 pp. 129133. 1838. 



