as affected by Induced Currents in an Iron Cylinder. 445 



periodic time, such a body would have to rotate at 7 x 10 14 revolu- 

 tions per second. 



I wish to thank Messrs. Siemens Bros, and Co. for the loan of the 

 field magnet, which was altered for the purpose of these experiments. 



I have pleasure in acknowledging the help I have received from 

 Mr. F. S. Robertson and Messrs. H. A. Skelton, R. M. Wartze, and 

 M. S. Duffitt. Mr. Skelton has spent a great deal of time in the 

 working out of the results. Mr. T. Jones has also rendered valuable 

 assistance. 



Table I. 



VOL. LXIX. 



2 I 



