Copy Letter from James Mackenzie Davidson, 26 Park Crescent, to William [Ramsay], FRS Asks William Ramsay for advice on a vacuum tube he wants made, particularly, on how best to get a stream of cathode rays outside a Crookes tube to be used on patients. Notes that he had a tube made to experiment with, however, it was imperfect and he is unsure how to be sure any rays got through the thin glass. Provides a sketch of what he envisions the tube to look and perform like. 29 October 1913