1883.] Prof. D. E. Hughes. On' a Magnetic Balance. 167 



December 20, 1883. 



THE PRESIDENT in the Chair. 



The Right Hon. Lord Justice Sir Edward Pry was admitted into 

 the Society. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read :— 



I. " On a Magnetic Balance, and Experimental Researches made 

 therewith." By Professor D. E. HUGHES, F.R.S. Received 

 December 10, 1883. 



In a paper " On the Molecular Rigidity of Tempered Steel,"* I 

 advanced the theory that the molecules of soft iron were comparatively 

 free as regards motion amongst themselves, whilst in hard iron or 

 steel they were extremely rigid in their relative positions. 



I have since widened the field of inquiry by observing the effects of 

 mechanical compression and strains, as well as annealing and tem- 

 pering, upon the magnetic capacity of sixty varieties of iron and steel, 

 ranging from the softest Swedish iron to the hardest tempered cast 

 steel. 



We know already that soft iron will take a higher degree of tempo- 

 rary magnetism than steel, and that tempered steel retains magnetism 

 more than soft iron ; consequently, we might believe that by the aid 

 of an instrument which should give correct measurements, we might 

 be able to include all varieties of iron and steel between the two 

 extremes of softness, as in annealed iron, and hardness, as in high- 

 tempered cast steel. This proved, however, not to be the case, if the 

 iron and steel were not all annealed to one absolute standard, and if 

 magnetised to or near saturation. 



In a late paper upon the theory of magnetism,f I said : — 

 " During these researches I have remarked a peculiar property of 

 magnetism, viz., that not only can the molecules be rotated through 

 any degree of arc to its maximum, or saturation, but that, whilst it 

 requires a comparatively strong force to overcome its rigidity or ± 

 resistance to rotation, it has a small field of its own through which it 

 can move with excessive freedom, trembling, vibrating, or rotating 



* " Proceedings Institution of Mechanical Engineers," January, 1883. 

 f Society of Telegraph Engineers, May 24, 1883. 

 VOL. XXXVi. N 



