492 MR JAMES RUSSELL ON THE SUPERPOSITION OF MECHANICAL VIBRATIONS 



vibrations and field. Change of field may be superposed upon continuously acting 

 vibrations of uniform intensity for the time being. Moreover, if the tapping be 

 described as " vigorous," it may be assumed that its effect upon magnetisation will have 

 reached a limiting value. If, however, we wish to investigate the effect of vibrations 

 within this limiting value, tapping the magnetic metal would afford a very imperfect 

 method of so doing. 



Many questions arise to which, so far as I know, no definite answers have been given. 



For instance : — What is the effect of superposing vibrations upon magnetisation, 

 relative to the effect of superposing magnetic change upon magnetic metals kept in 

 a state of continuous vibration ? What is the effect of superposing vibrations of 

 various intensities at all stages of cyclic fields ? If the vibrations be continuous, how 

 does the energy loss during a magnetic cycle vary with maximum field, how with 

 maximum induction ? In what metal, or in what condition of that metal, is any given 

 effect a maximum, or any given effect a minimum ? 



Further, it may well be asked whether the reduction of residual magnetisation by 

 vibration is a necessary consequence of the molecular theory of magnetisation. In the 

 present state of theoretical knowledge, would some such deduction as the following not 

 be equally valid ? Vibrations will give the molecular magnets intervals of freedom and 

 allow them to assume more stable positions when the magnetic force is acting, so 

 that when the force is withdrawn the residual magnetisation will be increased. 



The above queries indicate the scope of the present investigation. They were in 

 the first instance suggested by experiments upon the effects of electric oscillations on 

 the magnetic properties of iron.* Little doubt existed in the mind of the author that 

 the effects of mechanical vibrations would be found to be very similar to the effects of 

 electric oscillations, provided that in the experimental methods employed the same 

 distinction between the two methods of relative superposition of vibrations and field 

 — the importance of which was insisted upon — also obtained. 



Apparatus. 



To obtain satisfactory quantitative measurements, the vibrations must be produced 

 in such a way that they can readily be put " on " and " off," and that when on they 

 remain constant in character and intensity. Such a result was very approximately 

 attained by experimenting with wires attached to the gong of an ordinary electric bell 

 of substantial construction. The wires were hooked at their ends, and one extremity of 

 a wire could be linked into a small hole drilled near the edge of the gong, the other end 

 being linked to the vertical arm of an L-shaped lever, either directly or, preferably, by 

 means of a short length of thread. The latter method eliminates a possible source of 

 uncertainty in the results due to minute torsional effects, which were much greater in 



* " Notes on the Effect of Electric Oscillations (co-directional and transverse) on the Magnetic Properties of Iron," 

 Proc. R.S.E., vol. xxvi. p. 33, 1905. 



