FARADAV. 



that be required net, and it was not till 1845 that he entered on his 

 iwt period of research, in which he discovered the effect of magnetism 

 on poluJMid light, and the phenomena of diamagnetism. 



Faraday had for a long time kept in view the possibility of using a ray 

 of polarised light as a means of investigating the condition of transparent 

 bediss when acted on by electric and magnetic forces. Dr Bence Jones (Life 

 tf Parmiay, voL L p. 362) gives the following note from his laboratory book, 

 I0th September, 1822: 



ray of lamp-light by reflexion, and endeavoured to ascertain whether any depolarizing 

 (WM) curted on it by water placed between the poles of a voltaic battery and in a glass 

 . MW WoUMton'* trough tiled; the fluids decomposed were pure water, weak solution of 

 at cafe, and strong mlphuric acid; none of them had any effect on the polarized light, 

 out of or to the voltaic circuit, so that IK> particular arrangement of particles could be 

 in Uii* way." 



yean afterwards we find another entry in his note-book, on 2nd 

 May, 1833 (Lift by Dr Bence Jones, vol. ii. p. 29). He then tried, not only 

 the effect of a steady current, but the effect on making and breaking contact. 



" I do not think, therefore, that decomposing solutions or substances will be found to have (as 

 MMtyMM of decomposition or arrangement for the time) any effect on the polarized ray. Should 

 now tnr noa-dceofnponng bodies, as solid nitre, nitrate of silver, borax, glass, etc. whilst solid, to see 

 if aay iatanud cut* induced, which by decomposition is destroyed, Le. whether, when they cannot 

 any *Ute of electrical tension is present My borate of glass good, and common electricity 

 Uun voltaic." 



On May 6 he makes further experiments, and concludes " Hence I see 

 no reason to expect that any kind of structure or tension can be rendered 

 evident, either in decomposing or non-decomposing bodies, in insulating or con- 

 ducting states." 



:riments similar to the last-mentioned have recently been made by Dr 

 Kerr, of Glasgow, who considers that he has obtained distinct evidence of 

 action on a ray of polarized light when the electric force is perpendicular to 

 the ray and inclined 45* to the plane of polarization. Many physicists, how- 

 ever, have found themselves unable to obtain Dr Kerr's result. 



At last, in 1845, Faraday attacked the old problem, but this time with 



wnplete success. Before we describe this result we may mention that in 



he made the relation between magnetism and light the subject of his 



5ry last experimental work. He endeavoured, but in vain, to detect any 



