The Stress in Magnetised Iron

Abstract

DR. CHREE will meet, I think, with general support in his opposition to the view that there is of necessity, or even usually, an actual stress in a magnetised rod tending to shorten it; but in maintaining, as I understand him to do, the opposite view that the magnetic tension along the lines of force is necessarily accompanied by a mechanical stress of pull and the associated extension, he appears to me to be on more disputable ground. Dr. Chree's conception of the Maxwell distribution of stress seems, if I may venture to say so, to be too materialistic. What Maxwell really showed, of course, was that such a distribution would produce on every element of matter in the field the mechanical force which it was known actually to experience. It was not suggested, however, that these stresses were to be considered as transmitted by the matter by virtue of its mechanical properties, indeed this could clearly not be the case where the matter was liquid or gaseous; and so there are no grounds for supposing that the matter would exhibit strains directly associated with these stresses. The stresses, in fact, must be considered as transmitted by the ether which pervades the field, and it is in the ether that the associated strains are to be looked for.