26 MR. H. TOMLINSON ON THE INFLUENCE OF STRESS AND STRAIN, ETC. 



of the amplitude even for the very minutest torsional deformations ; but, since it ha8 

 been proved that any magnetic stress, however small, must produce some molecular 

 permanent set, the difficulty vanishes.] 



Summary. 



1. When the deformations produced by the oscillations are small the internal 

 friction of a torsionally vibrating wire is not affected by sustained longitudinal mag- 

 netisation of moderate amount. The internal friction is also not affected by sustained 

 magnetisation, even when carried nearly to the point of saturation, provided the 

 magnetising current be, previously to experimenting, reversed a great number of times. 



2. When the deformations are large the internal friction is increased by sustained 

 magnetisation of large amount. 



3. The torsional elasticity is entirely independent of any sustained longitudinally 

 magnetising stress which may be acting upon the wire, provided the deformations 

 produced by the torsional oscillations be small. When the deformations are large the 

 torsional elasticity is very slightly decreased by sustained longitudinal magnetisation 

 of large amount. 



4. When the magnetising current is interrupted, and, to a greater extent, when it 

 is reversed repeatedly whilst the wire is oscillating, the internal friction is increased 

 provided the magnetising stress be of moderate amount. The increase of internal 

 friction may become very considerable when the magnetising stress is great. 



5. When the deformations produced by the oscillations are small the torsional 

 elasticity is not affected by either repeatedly interrupted or reversed magnetisation, 

 even when the magnetising current is very large. 



6. There exists a limit of magnetic stress within which the magnetic elasticity is 

 sensibly perfect, but a mathematically true magnetic elastic limit does not exist. 



7. The passage of an electric current through a torsionally vibrating wire does not 

 affect, except by heating, either the internal friction or the torsional elasticity, provided 

 the deformations produced by the oscillations be small. 



8. The effect of longitudinal magnetisation, even when carried to the point of 

 saturation, on the longitudinal oscillations of an iron or steel wire is nil. 



9. The passage of an electric current through a longitudinally oscillating iron or 

 steel wire does not, except by heating, affect the oscillation-frequency. 



10. When the deformations produced in a torsionally oscillating wire do not exceed 

 a certain limit the internal friction mainly depends upon the sub-permanent rotation 

 to and fro of the molecules about their axes. 



