The Stress in Magnetised Iron

Abstract

I AM glad that Dr. Chree, in his letter published in NATURE of January 23, has raised a discussion of this matter, regarding which, as he says, the most contradictory statements are to be found. For some time I have been aware that the passage referred to in my book on “Magnetic Induction in Iron” requires correction. The magnetic stress, B²/8π, in a long rod or ring uniformly magnetised, is there spoken of as if it were of the same nature as a simple longitudinal stress of compression, producing a contraction of the length in consequence of the elasticity of the metal. Dr. Chree, if I understand him rightly, would treat it as of the same nature as a simple longitudinal stress of tension, producing an elongation of the iron.