DR. KARL, T. COMPTON, while professor of physics in Princeton University, performed and inspired a great deal of work on the phenomena of the electric discharge in gases, on the emission of electrons from surfaces and on ionization by electron impact. He is now president of the Massachusetts Institute of Technology. His article on “The Electron: its Intellectual and Social Significance” published as a supplement in this issue (p. 229) contains a survey, written in general terms, of the development of our knowledge of the electron since its discovery at the end of last century. The discovery of the electron, and the application of the electron ideas, first to gas discharges, then to radioactivity, spectroscopy and atomic structure, opened a most rapid advance in physical science, leading up to contemporary views of atomic structure and of chemistry. Applied to technical sciences, particularly in the communication industries, the electron has assumed great commercial and social significance.