ROTATIXO A DIELECTRIC IN A MAGNETIC FIELD. 137 



The results obtained are consequently in complete agreement with MAXWELL'S 

 electromagnetic theory, as developed by H. A. LORKNTZ and LARMOR. 



According to HKRTZ'S form of MAXWKLL'S theory the induced electromotive force 

 in a dielectric is equal to that in a conductor. The experiment descril>ed may 

 consequently l)e i-egarded as a crucial exj>eriment deciding in favour of LORKXTZ and 

 LARMOR'S theory and against HKRTX'S theory. 



In conclusion, 1 wish to say that I am indebted to Professor LARMOR for valuable 

 advice and help with regard tx> the theory of the experiment. My best thanks are 

 also due to Professor J. J. THOMSON for his never failing encouragement and valuable 

 suggestions given throughout the course of the work, which was done in the Cavendish 

 Laboratory. 



Vol.. (VI V. - A. 



