Letter from Frederick Soddy, FRS, Chemical Laboratory, Glasgow University, to James Mackenzie Davidson Informs Mackenzie Davidson that the initial gamma rays from the thorium deposit will be the same as that from radium in a tube, though they decay rapidly. Notes that the same applies for the beta rays, while the alpha rays will be present in a lesser amount than that from the radium. Discusses the decay time of thorium emanation. 28 November 1911