UPON MAGNETISATION, AND CONVERSELY, IN IRON, STEEL, AND NICKEL. 515 



independent field (which may be zero) are essentially the same as those produced by 

 purely mechanical vibrations. 



Within the limits stated under (1), (2), and (3), the effects of vibrations upon 

 magnetisation exhibit striking differences between iron, steel, and nickel in the annealed 

 and in the quenched conditions, which involve, more especially under (3) with cyclic 

 fields, a complete study of the curves in each case (see summary of experimental 

 results). The investigation cannot in any sense be regarded as exhaustive. Many 

 additional inquiries present themselves, among which the following may be mentioned : 

 — If the vibrations were such as to exhaust the possible increase of induction with 

 increasing field, would hysteresis loss (for instance) be decreased instead of increased 

 for the same value of low field at cyclic extremes ? Under the same conditions, would 

 residual magnetisation in quenched nickel be decreased instead of increased for the 

 same value of low induction at cyclic extremes ? The induction reached when 

 vibrations are superposed (A conditions) is greater in nickel, less in iron and steel, 

 than one-half the induction change on reversals when vibrations are superposed 

 (B conditions). Does this fact throw any light on the relative inter-molecular 

 controlling forces as they exist in these different metals ? 



In conclusion, this investigation was, as has already been pointed out, directly 

 suggested by previous work on the effects of electric oscillations upon magnetisation, 

 with which it is intimately associated. The results and suggestions obtained with 

 purely mechanical vibrations undoubtedly facilitate further investigation in its 

 theoretical and practical aspects (magnetic detectors) dealing with the primary objects 

 of those researches for which the Royal Society of London placed at my disposal a 

 Government grant, which I desire to acknowledge. 



I also desire to express my indebtedness to Dr Peddie for advice kindly given at all 

 times ; and to Professor Macgregor for facilities to quench the wires, which I did not 

 possess. 



(Read December 17, 1906.) 



In a paper* on "The Effect of Electric Oscillations on Iron in a Magnetic 

 Field," read to the Physical Society on 22nd June 1906, Dr Eccles, in referring to my 

 paper (Proc. R.S.E., vol. xxvi. p. 33) on the same subject, states : " Russell applied 

 to his iron the oscillations passing through a coil connected directly in series with a 

 small induction coil. This last method appears to the writer to subject the iron to 

 very violent treatment of a nature not easily described accurately ; for how far the 

 mere surgings of secondary current overwhelm in importance the genuine oscillations, it 

 will be difficult to say." 



I formally assumed that the effects upon magnetisation of oscillations produced as 

 above described would not differ essentially from oscillations produced in wires by 

 means of Hertz waves. 



* Phil. Mag., August 1906 ; Electrician, August 24, 1906. 



TRANS. ROY. SOC. EDIN., VOL. XLY. PART II. (NO. 17). 72 



