'228 



Mr. H. Tomlinsou.' The Influence of [Mar. 31, 



lity seems to occur at nearly the same point of magnetic intensity 

 for different specimens of well-annealed iron of good magnetic permea- 

 bility, but not at the same point of magnetising force. 



23. When an iron wire has received previous magnetisation the point 

 of maximum permeability occurs with a higher and higher magnetising 

 force as the previous permanent magnetisation increases. 



The point of maximum permeability also occurs at a higher degree 

 of magnetic intensity when the wire has been previously subjected to 

 a high magnetising force. 



24. Besides a point of maximum total permeability there is a point 

 of maximum temporary permeability which occurs a little before the 

 first-mentioned point. 



24 and 23 are in accordance with Maxwell's extension of Weber's 

 theory. 



25. The temporary permeability is diminished by previous per- 

 manent or subpermanent magnetisation in the same direction. The 

 effect above mentioned may be very considerable, provided the mag- 

 netising force lies between certain limits. 



26. When the wire is well shaken after having been previously 

 magnetised by a strong force the temporary permeability is consider- 

 ably restored, and is, moreover, much more nearly a constant for 

 different values of the magnetising force than it was either previously 

 to shaking or previously to suffering permanent magnetisation. 



27. More than 90 per cent, of the whole magnetisation imparted 

 by a given force to annealed iron maybe permanent or subpermanent 

 provided the magnetising force has a certain moderate value.* When, 

 however, the force is very large the percentage of permanent mag- 

 netism is much diminished. 



28. When an iron wire is loaded to a certain limit longitudinal 

 magnetisation has no effect on the thermo-electrical qualities of the 

 metal. 



The limit of loading mentioned above seems to be the same for a 

 given magnetising force, as that at which magnetisation has no effect 

 on the dimensions of the wire. 



29. The general features of the curves showing the relation 

 between temporary magnetic permeability and load are the same for 

 nickel as for iron. 



30. There are two critical points of loading at which the load has 

 no effect on the temporary magnetic permeability of nickel. 



31. The load at the first critical point diminishes with diminution 

 of the magnetising force and finally vanishes. 



* This has been already noticed by Ewing ('Phil. Trans.,' 1885, Part II), in 

 whose important memoir other points of interest connected with magnetic induction 

 wLich are mentioned in this paper have been also discussed. 



