■i)2'6 Dr. A. 0. Rankine and Dr. E. B. Young on the 

 where the expansion of the typical S.F. element is 



S(#-2arp + f*)=2(?~, or a ~)l.( M ), . (11) 



= P«+ L -/*P, = mP. -P,,-! = Ph +i-P, -] 



H » + 1 2;j + 1 



(12) 



Dr. Bromwich's recurring- relations for his S„, S,/ (Phil. 

 Mag. July, p. 159), are then the equivalent of the definition 

 of C n (x) in § 1, or of the differential ecj nation (5) in § 1, 

 written in a sequence equation, as in (3) § 13. 



1 Staple Inn, W.C. 1. 



Auprust 11, 1919. 



LI I. On the Magnetic Effects of Vibration in Iron Rods. 

 By A. 0. Rankine, D.Sc, and F. B. Young, D.Sc. 9 



IN ' Magnetic Induction in Iron and other Metals ' (p. 227) 

 Ewing describes an experiment by means of which may 

 be demonstrated the variation in the magnetic state of iron 

 which accompanies mechanical strain. A knowledge of the 

 electrical and magnetic changes produced by mechanical 

 vibration in iron being required in connexion with certain 

 investigations, the following experiments, suggested by 

 Ewing's work, were carried out. 



Method of Experiment. 



A cylindrical solid rod K of mild steel G ft. long and 1 inch 

 in diameter was clamped at its centre. A conductor of low 

 resistance connected the two ends to form a closed circuit 

 which could, however, be open at will by means of the 

 included switch S. At one end of the rod and at right 

 angles to it was fixed a short brass lever L. By striking 

 with a lead bar the lever, the end of the rod or the side of 

 the rod, the latter could be thrown into torsional, longi- 

 tudinal or lateral vibration respectively. 



Observations were made with a small search-coil G. 5 inches 



* Communicated by Professor J. C. McLennan, Ph.D.. F.R.S. 



