XXV. Contributions to the molecular theory of induced magnetism

A S the facts of induced magnetism become better known, increasing interest attaches to molecular theories and increasing difficulty attends the theories that are current.Weber's fundamental conception that the molecules of iron or nickel or cobalt are always magnets, and tha~ the process of magnetizing consists in turning them from many directions towards one direction, has been strongly confirmed by the now well-established fact that there is a true saturation value, a finite limit to the intensity of magnetism, which may be reached or very closely approached by using a strong magnetic forcer.Without going further back, to enquire (with Amphre) how the molecules come to be magnets, we may take this conception as the natural starting-point of a theory.But when we go on to examine the conditions of constraint on the part of the rotatable molecules which have been suggested to make the theory square with what is known about permeability, about residual magnetism and other effects of magnetic hysteresis, about the effects of stress, of temperature, of mechanical vibration, and so forth, we find a mass of arbitrary assumptions which still leave the subject Communicated by the Author, having