THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOTJKNAL OF SCIENCE. 



[FIFTH SERIES.] 



MARCH 1896. 



XXI. On Magnetic Tractive Force * '. By E. Taylor Jones, 

 D.Sc.y Assistant Lecturer in Physics in the University College 

 of North Wales, formerly Science Scholar of Royal Commis- 

 sion for Exhibition of 1851 f. 



IN a former paper % an account was given of experiments 

 in which the value of the magnetic tractive force of a 

 divided ellipsoid was found to agree within 1 per cent, with 

 Maxwell's expression B 2 /87r for the electromagnetic stress in 

 the narrow air-space between the two halves, for inductions 

 between 6000 and 20,000 C.G.S. 



In the present paper further experiments will be described, 

 the chief object of which was to test whether the same agree- 

 ment existed at much higher inductions. Since the magne- 

 tizing force H in the iron was very small in comparison with 

 the induction B in the former experiments, these cannot be 

 considered as deciding between Maxwell's expression B 2 /87T 

 and, for instance, the expression 27rl 2 , which has also been 

 given as the value of the tractive force §. 



In order to complete the test it was necessary to continue 

 the experiments to such high inductions that the magnetic 

 force H was a considerable part, numerically, of the induction 

 H + 4ttI. 



* Partly communicated to the Physikalische Gesellschaft of Berlin on 

 June 28, 1895. 



t Communicated by the Author, in continuation of the paper on 

 a Electromagnetic Stress," Phil. Mag. March 1895. 



% E. T. Jones, Phil. Mag., March 1895 j Wie&.Ann. liv. p. 641 (1895). 



§ Stefan, Wien. Ber. lxxxi. 2 Abth. p. 89 (1880). 



Phil Mag. S. 5. Vol. 41. No. 250. March 1896. M 



