Paper, 'On the superficial viscosity of water' by Lord Rayleigh [John William Strutt] Strutt writes: 'The idea that liquids are endowed with a viscosity peculiar to the surface is to be found in the writings of Descartes and Rumford; but it is to Plateau that its general acceptance is due. His observations related to the behaviour of a compass needle, turning freely upon a point, and mounted in the centre of a cylindrical glass vessel of diameter not much more than sufficient to allow freedom of movement. By means of an external magnet the needle was deflected 90° from the magnetic meridian.' Annotations in pencil and ink. Subject: Physics Received 15 May 1890. Read 5 June 1890. A version of this paper was published in volume 48 of the Proceedings of the Royal Society as 'On the superficial viscosity of water'. 1890