Mechanical Vibrations upon Magnetization. 475 



the same in both cases facilitates comparison. Under both 

 the A and B conditions (omitting minor differences between 

 codirectional and transverse oscillations) the similarity extends 

 to details. 



Conclusion. 



A Conditions. — The effects of mechanical vibrations (sum- 

 marized above) or of electric oscillations, superposed at all 

 stages of the normal loop, are, generally speaking, to lessen 

 those differences of magnetization to which hysteresis without 

 vibrations lias already given rise. 



B Conditions. — When change of field is superposed upon 

 permanently acting mechanical vibrations or electric oscil- 

 lations, the results (summarized above, in the case of vibra- 

 tions) cannot be concisely stated in terms of hysteresis. 

 They are, however, subject to this condition, that vibrations 

 or oscillations increase the differential permeability in low 

 fields, decrease it in high fields. In sufficiently high fields 

 vibrations or oscillations must delay demagnetization. 



This investigation affords a general survey of the effects 

 of vibrations upon magnetization under two distinct methods 

 of relative superposition of vibrations and field, and cannot 

 be regarded in any sense as exhaustive. It was directly 

 suggested by previous work on the effect of electric oscilla- 

 tions upon magnetism, with which it is intimately associated. 

 The results obtained with vibrations undoubtedly facilitate 

 further investigation in its theoretical and practical aspects 

 (magnetic detectors) dealing with the primary objects of 

 these researches, for which the Royal Society of London 

 placed at my disposal a Government grant, which I desire to 

 acknowledge. 



Addendum. 



In a paper on " The Effect of Electric Oscillations on Iron 

 in a Magnetic Field w * 5 read to the Physical Society on 

 June 22, 1906, Dr. Eccles, referring to my previous paper 

 (mentioned above), calls attention to the fact that I applied 

 to the iron " the oscillations passing through a coil connected 

 directly in series with a small induction-coil/'' On July 14 

 and 15 last I experimented with oscillations produced in the 

 usual way by means of two small Leyden jars, induction-coil, 

 spark-gap, and oscillation -transformer. The oscillations 



* Phil. Mag. August 1906. ' The Electrician,' August 24, 1906. 

 ' Science Abstracts,' vol. ix. A. Abstract 1619. 



