With the minimum amount of simple mathematics, the author has compiled in this small volume a splendid series of articles on the fundamental nature of electricity. A physician having an elementary knowledge of college physics should enjoy reading about some of the recently advanced theories concerning electricity. Electromagnetic radiation, roentgen rays, light, photo-electrical effects and the electron are dealt with in simple, readable language. The scientific aspects of the problems have not been unduly strained for simplicity's sake. A physician specializing in roentgen therapy or ultraviolet radiation therapy will probably find this volume a worth while addition to his library.