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Mr. H. Tomlinson. The Influence of [Mar. 31, 



7. The minimum temporary permeability increases with the mag- 

 netisingforce tip to a certain limit of the latter, but beyond this limit 

 decreases. 



8. The permanent magnetic permeability is increased by loading, the 

 amount of increase per cent, being very large for small magnetising 

 forces and moderate loads, but diminishing as the magnetising force 

 increases. 



9. The increase of permanent magnetic permeability mentioned in 

 8 rises in greater proportion than the load up to a certain limit of 

 the latter. Beyond this limit it rises in less proportion than the load, 

 and eventually ceases to rise with increase of load ; the value of the 

 load at which this last occurs decreases as the magnetising force is 

 increased. 



10. For a wide range of loading, the effect of the stress on the 

 permanent permeability is opposite in direction to the effect on the 

 temporary permeability. Consequently loading may be found to pro- 

 duce either increase or decrease of permeability according as the 

 permeability we are considering is temporary or permanent. 



Similarly the total magnetic permeability, since it includes both 

 temporary and permanent permeabilities, may be affected by loading 

 in the contrary direction to the temporary magnetic permeability, and 

 the more so as the effects of loading on the permanent magnetic 

 permeability are very much larger than those on the temporary 

 magnetic permeability for a rather wide range both of loading and of 

 magnetising force. 



11. The effect of loading — even when carried to a great extent — on 

 the temporary permeability of unannealed piano-steel is very small, 

 provided the wire be not permanently stretched by the load. 



12. The effect of loading on the magnetic permeability of annealed 

 iron varies very considerably with the amount of previous strain to 

 which the metal has been subjected. 



13. When the magnetising force is very considerable and the load 

 small, permanent extension, resulting from previous loading, causes 

 the diminution of temporary permeability produced by the load to be 

 much increased ; also the maximum diminution which can be tempo- 

 rarily produced by loading is increased. 



When, however, the temporary load exceeds a certain limit, the 

 diminution of temporary permeability produced by the load is lessened 

 by permanent extension. Further, the load which produces maximum 

 diminution of temporary permeability may be considerably lessened 

 by permanent extension. 



14, When the magnetising force is small the permanent strain may 

 change increase of temporary magnetic permeability resulting from 

 loading to decrease, provided the load does not exceed a certain 

 limit. 



