1886.] Stress and Sti'ain and the Properties of Matter, 447 



experimenting here, therefore, was to take the rhythm of the heart, or 

 the excitability of the nerve, immediately before screwing up the 

 apparatus, and again immediately after taking it down. I was thus 

 unable to observe the effects of the pressure during the time that it 

 was being actually applied ; but as it only took me a quarter of a 

 minute to unship the chamber and turn its contents out on the table, 

 if the 150 atmospheres had exerted any marked influence on the 

 excitability of the tissues, it would probably have been easily detected 

 by this method. Yet neither the heart nor the nerve showed any 

 change after an exposure of five minutes to this great increase of 

 pressure. 



VI. " The Influence of Stress and Strain on the Physical Pro- 

 perties of Matter. Part L Elasticity — continued. The 

 Effect of Magnetisation on the Elasticity and the Internal 

 Friction of Metals." By Herbert Tomlinson, B.A. Com- 

 municated by Professor W. Grylls Adams, M.A., F.R.S. 

 Received May 18, 1886. 



(Abstract.) 



The principal object of this investigation was to test the sound- 

 ness of the view advanced by Professor G. Wiedemann respecting 

 the cause of the internal friction of a torsionally oscillating wire.* 

 According to this view the internal friction is mainly due to per- 

 manent rotation to-and-fro of the molecules about their axes ; it 

 seemed probable, therefore, that experiments on the effects of 

 magnetising a wire either longitudinally with a helix or circularly 

 by passing a current through it would aid in elucidating the matter. 



In the experiments on the effects of longitudinal magnetisation 

 arrangements were made so that the heat generated in the magne- 

 tising helix should not reach the wire, whilst the effect of the heat 

 generated in the wire when an electric current was passed through 

 it was eliminated in a manner which is fully described in the paper. 



Besides the experiments on the effect of magnetisation on the 

 internal friction and on the torsional elasticity of metals, others 

 were made relating to the longitudinal elasticity of metals. The 

 following are the principal results which have been obtained : — 



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

 the internal friction of a torsionally vibrating wire of iron or steel is 

 not affected by sustained longitudinal magnetisation of moderate 

 amount. The internal friction is also not affected by the sustained 

 magnetisation even when the latter is carried to the point of satura- 



* " Wiedemann's Annaleu," N.F., Bd. vi, p. 485. 



