Unpublished paper, 'On the velocities of two distinct groups of secondary corpuscular rays produced by a homogeneous Röntgen radiation and their absorption coefficients in various gases' by Lewis Simons The object of the paper is to investigate the absorption coefficients of the secondary corpuscular rays in various cases and to find, if possible, a velocity distribution, from the maximum downwards, of the particles about the radiator. Annotations in pencil and ink throughout. Subject: Physics Received 14 October 1918. Communicated by [Owen Willans] Richardson. A version of this paper was published by Simons in the Transactions of the Royal Society of South Africa: Simons, Lewis. 'On the velocities of two distinct groups of secondary corpuscular rays produced by a homogeneous Röntgen radiation and their absorption coefficients in various gases.' The Transactions of the Royal Society of South Africa, volume 8, number 1 (1919), pp. 73-86. 1918