Although determinations of the magnetic permeability of nickel have been made by Rowland and others, there appears to be no published investigation of the effect of cyclic magnetising processes. The study of such processes is interesting not only in its direct bearing on the relation of magnetisation to magnetising force, but indirectly as yielding data from which one may calculate the dissipation of energy that occurs in reversal or other variation of magnetism, in consequence of hysteresis in the relation of magnetisation to magnetising force. Cyclic processes have been very fully examined for various kinds of iron and steel, and one object of the following experiments was to obtain information of the same kind with regard to nickel. Another object was to examine the effects of longitudinal stress on the magnetisation of this metal in the same manner as they had been examined in iron by one of the writers. Sir William Thomson’s early results in this subject had shown that, when subjected to longitudinal pull, nickel undergoes much change of magnetism, of a kind opposite to that which ordinarily occurs in iron, and it seemed that a fuller investigation of the effects of stress might be useful. The experiments, with the exception of one group described at the end of this paper, were made with specimens of nickel wire supplied by Messrs. Johnson and Matthey. The wire was 0.068 cm. in diameter, and was supplied in what appeared to be a hard-drawn state, in which its magnetic susceptibility was decidedly less than when the wire was annealed. Its magnetic quality was examined both when in this hard-drawn state and after annealing. The direct magnetometric method was employed, in the same manner as in the experiments on iron referred to above.