TO THE THEORY OF MAGNETISM. 



115 



quantity K, which depends on f, the measure of the coercive 

 force. 



The table page 87 of the volume just cited, contains another 

 set of observed torsions, for different lengths of a much finer 



1 / 38 



wire whose radius a = */ - : hence we find the correspond- 

 ing value of /3 = 3,1 3880, and the first observation in the table 

 gives ^T=.6448. With these values the last column of the 

 following table has been calculated as before : 



Here also the differences between the observed and calculated 

 values are extremely small, and as the wire is a very fine one, 

 our formula is applicable to much shorter pieces than in the 

 former case. In general, when the length of the wire exceeds 

 10 or 15 times its diameter, we may employ it without hesita- 

 tion. 



82 



