In June of last year one of us gave before the Society a short account of certain preliminary experiments on the volume effects of magnetisation. These experiments had been made in Japan; and the results obtained evidently called for a more thorough investigation. The facilities of the Physical Laboratory of Edinburgh University were kindly placed at our disposal by Professor Tait. Five tubes of Swedish iron, all cut from the same original bar but made with different bores, were prepared for study in much the same manner as formerly. Many experimental difficulties encountered us; and only now have these been satisfactorily overcome. For it must be remembered that the effect to be observed is very minute, and can be measured only in one way, viz., by the motion of the meniscus along the narrow capillary tube which is in connection with the iron tube, the whole being filled with fluid. But such an arrangement is obviously a very delicate thermometer; and, as a matter of fact, we have seldom got the meniscus really steady. Generally it is moving at a rate which, though as inappreciable to the naked eye as the motion of an hour hand, is only too evident under the microscopic power necessary for the observation of the magnetic effect.