446 Mr. W. Sturgeon on the Theory of Magnetic Electricity. 



To convince any person of the influence of the modulus of 

 elasticity of metals on the musical sound produced by them, 

 let them have a tuning-fork made of bell-metal, of the same 

 length and thickness as a fork made of steel : they will find 

 the note given by the bell-metal fork a fifth lower than the 

 note from steel. 



The stiffness of gold, against taking a permanent set or 

 flexure, I find about fths of that of brass; £th of the stiffness 

 of wrought iron, and £th of that of untempered steel. 

 I am, Gentlemen, yours truly, 



B. Bevan. 



LXXV. On the Theory of Magnetic Electricity . By Mx.Wm. 

 Sturgeon, Member of the British Association for the Pro- 

 motion of Science ; Lecturer at the Hon. East India Com- 

 pany's Military Academy, Addiscombe, fyc. fyc. 



[Concluded from p. 371.] 



T N the positions which I have advanced for exhibiting the 

 -*- proximate laws of magnetic electricity, I have carefully 

 avoided every consideration that could possibly embarrass the 

 mind, or prevent them from being understood. They would 

 virtually, however, have been but very little affected by taking 

 into account the magnetism of the metal as an intermediate 

 agent in the process of excitation ; but they are much simpli- 

 fied by omitting those remote laws, which would be better ex- 

 hibited separately, and as a distinct class, which may be admit- 

 ted, or rejected, at pleasure, without affecting the calculations 

 of the experimenter. 



Position 7, with its illustrations, will explain the apparent 

 anomalies in the direction of the electric current in wires, when 

 excited at various parts of the surface of the magnet; and will 

 show that, with respect to the exciting polar magnetic lines, the 

 direction of the current is constantly the same. 



The electrical vortices also, both simple and compound, as 

 I have discovered them to be exhibited by plates and discs, 

 whether rotating on an axis, or moving in right lines, may very 

 easily be explained by the same position. 



The simple vortex represented in fig. 24. (Plate I. vol. i.) 

 may be regarded as the ring with its exciting polar lines, in 

 fig. 7 and 8. PL I. of the present volume, in an inverted order; 

 having the marked ends of the exciting lines downwards in- 

 stead of upwards, which is the case in all the figures of the 

 former plate. 



In fig. 23. (Plate I. vol. i.) the ring may be supposed to be 



