Manchester Memoirs, Vol. Iviii. (19 14), No. 11. 3 



this intrinsic field cannot be readily explained according 

 to recognised laws. If such a field exists its lines of force, 

 if uniform, apparently do not extend to the outside of the 

 magnet, and the fact that a very small reverse applied 

 force easily demagnetises a magnet is a difficulty in 

 accepting the idea of an intrinsic field of large magnitude. 



It is therefore desirable to look for additional evidence 

 either for or against the existence of such a field and the 

 following experiment supplies further information on the 

 question. 



Let two iron wires of the same structure dip into the 

 limbs of a U-tube filled with a suitable electrolyte. If one 

 of the limbs be placed between the poles of an electro- 

 magnet an electro-motive force is established between the 

 wires of such kind that the magnetised wire acts to the 

 unmagnetised like copper to zinc in a simple cell. This 

 can be explained by considering the iron ions as tending 

 to pass into solution, but where there is a magnetic field 

 the magnetic ions are held back and thus more positively 

 charged iron ions pass from the unmagnetised than from 

 the magnetised electrode into the solution, and hence the 

 current is from the unmagnetised to the magnetised 

 electrode through the solution. 



The experiment arranged in this way has been carried 

 out in recent years by Hurmuzescu* in fields up to 7,000 

 gausses, and by R, Paillot^ in fields up to 30,000 gausses 

 with concordant results. The latter finds a maximum of 

 electro-motive force developed in afield of 25,000 gausses. 



Assuming that the electro-motive force arises from the 

 magnetisation of the iron the experiment can be sub- 

 mitted to calculation by applying the hypothesis that the 

 electrical work is the equivalent of the magnetic work. 



V- dePkys., (3), t. iv., p. ii8. 1895. 

 ^ Comptes Rendus, 131, pp. 1 194-5. 1900. 



