Letter from J. H. Gardiner, 59 Wroughton Road, Balham, to James Mackenzie Davidson Proposes that he and Mackenzie Davidson agree upon a common nomenclature. Suggests calling Mackenzie Davidson's rays Mural rays (M rays), those that are produced upon the walls of the tube by the action of paracathodic rays, while x-rays will be those generated where the focus of the cathode stream falls. Notes that his own progress is slow, with the double bulb tube taking a long time to make. Describes to Mackenzie Davidson a small, 'first step' experiment on paracathodic rays that he has set up in the meantime. Provides a small illustration of the experimental tube he is using. 30 January 1912