Determinations of Magnetic Susceptibility. 



445 



tribution becomes nearly, if not altogether, solenoidal, when the force 

 is made so high as to give the wire the maximum magnetisation. 

 More or less similar facts can be arrived at from the results for other 

 wires, and also those for the bars. 



These facts are truly interesting, seeing that they entirely agree 

 with theoretical considerations. Indeed they have been pointed out 

 theoretically by Sir William Thomson,* and indicated experimentally 

 by Rowland. f But I believe my experiments are the first, the results 

 of which have brought out those facts so clearly as not only to leave 

 no room for doubt, but also to enable us to see the law by which the 

 change in the distribution of magnetism in a cylindrical rod due to 

 the change of magnetising force to which it is subjected, is governed ; 

 and I hope they will be of service in guiding the future investigators 

 of electro-magnetism or otherwise. 



It is impossible for me to conclude this paper without expressing 

 my most grateful thanks to Sir William Thomson for the very kind 

 guidance and instruction he has given me in the course of these 

 experiments. 



* Papers on " Electricity and Magnetism," § GG7. 

 f " Phil. Mag.," August, 1873, p. 142, 



