136 CORRELATION OF PHYSICAL FORCES. 



universe would be the same as at present, but it would really 

 be the same result as though there were no energy at all, as 

 none could act, all would be in a state of unchanging stable 

 equilibrium ' and everything be nought.' 



As with heat, light, and electricity, daily accumulating 

 observations tend to show that each change in the phenomena 

 to which these names are given is accompanied by a change 

 either temporary or permanent in the matter affected by them ; 

 so many experiments on magnetism have connected magnetic 

 phenomena with a molecular change in the subject-matter. 

 In addition to the cases previously given the following may be 

 mentioned out of many. M. Wertheim has shown that the 

 elasticity of iron and steel is altered by magnetisation ; the 

 coefficient elasticity of in iron being temporarily, in steel per- 

 manently diminished. 



He has also examined the effects of torsion upon mag- 

 netised iron, and concludes, from his experiments, that in a 

 bar of iron arrived at a state of magnetic equilibrium, tem- 

 porary torsion diminishes the magnetism, and that the 

 untwisting or return to its primitive state restores the original 

 degree of magnetisation. 



M. Guillemin observed that a bar slightly curved by its 

 own weight is straightened by being magnetised. Mr. Page 

 and Mr. Marrion discovered that a sound is emitted when iron 

 or steel is rapidly magnetised or demagnetised ; and Mr. 

 Joule found that a bar of iron is slightly elongated by mag- 

 netisation. 



Again, with regard to diamagnetic bodies. M. Matteucci 

 found that the mechanical compression of glass altered the 

 rotatory power of magnetism upon a ray of polarised light 

 which the glass transmitted. He further considered that a 

 change took place in the temper of portions of glass which he 

 submitted to the influence of powerful magnets. 



The same arguments which have been submitted to the 

 reader as to the other affections of matter being modes of 

 molecular motion, are therefore equally applicable to mag- 

 netism. 



