LONDON. Physical Society, January 22.—Prof. Ayrton, Vice-President, in the chair.—Mr. Croft gave an exhibition of some simple apparatus. The exhibition included an ingenious form of clip to fit on an upright retort stand; a Nicol used for projecting the rings and brushes in crystals, with which it is sufficient to use the ordinary condenser of the lantern, the source of light having been moved further away from the lens than is usual; some photographs showing caustics, conical refraction, and diffraction; a stand for magnets, &c, when demonstrating the attraction and repulsion of poles; a stand for the suspension of objects for experiments on diamagnetism; a holder for X-ray tubes consisting of a spiral of wire fitting round the exhaustion tube of the bulb; an X-ray photograph taken by means of a Wimshurst machine; a model of Michelson's interference experiment; an arrangement to show subjective colours, in which a double lantern is arranged to give two partly over-lapping discs.