﻿THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



NOVEMBER 1894. 



LII. Wave-Lengths of Electricity on Iron Wires. 

 By Charles E. St. John, A.M.* 



[Plate XII.] 



THE question whether the magnetic properties of iron are 

 called into play under extremely rapid alternations of 

 the magnetizing forces is an interesting one, and has received 

 various answers. 



Hertz found negative results when he replaced one side of 

 a rectangular copper resonator f by an equal iron wire ; and 

 in a later paper, on the " Finite Velocity of Electromagnetic 

 Action "t, when he compares the rate of propagation along 

 copper and iron wires, he concludes " that the rate of propa- 

 gation in all wires is the same, and we are justified in speaking 

 of it as a definite velocity. Even iron wires are no exception 

 to this general rule ; hence the magnetic properties of the iron 

 are not called into play by such rapid disturbances w § . 



Dr. Oliver J. Lodge attacked the question by means of his 

 experiment on the alternate path. In his * Lightning Con- 

 ductors and Lightning Guards' (1892), he remarks : — " But 

 everyone will say — and I should have said before trying — 

 surely iron has more self-induction than copper. A current 



* Communicated by Prof. J. Trowbridge. 



t Wied. Ann. xxxi. p. 429 (1887). % Ibid, xxxiv. p. 351 (1888). 



§ 'Electric Waves,' p. 113. 



Phil. Mag. S. 5. Vol. 38. No. 234. Nov. 1894. 2 G 



