Paper, 'Some measures of Young's modulus for crystals, &c' by A [Arnulph] Mallock Mallock writes: 'The Table at the end of this communication contains the results of: experiments made in October, 1889—February, 1890, on the elasticity of various bodies. The measures relating to crystalline bodies are, I believe, new. The method used to obtain these results was applicable to very small specimens. This was a necessary condition in the case of most crystals, because of the difficulty of getting large specimens without flaws. In the experiments now to be described, I am dealing only with the values of Young's modulus, but by a modification of the apparatus measures can be made of the simple rigidity, which will, I hope, form the subject of a future communication.' Annotations in pencil and ink. Includes 15 diagrams of experimental apparatus and results. Subject: Physics / Crystallography Received 9 March 1891. Read 19 March 1891. Communicated by Lord Rayleigh [John William Strutt]. A version of this paper was published in volume 49 of the Proceedings of the Royal Society as 'Some measures of Young’s modulus for crystals, &c'. 1891