This book might be termed a textbook on radiation. The effects of radiant energy have been coordinated with the physics of the subject, making a combination that should be helpful both in biologic research and in therapeutic practice. The important subjects discussed include: solar radiation, effects of spectral energy, reflection of ultraviolet radiation, transmitting mediums, infra red radiation, permanency of materials, incandescent solids, measurement of ultraviolet radiation and electric arcs. The final chapter deals with the utilization of lighting for the best effects. This book is interesting and well written, and should be of value not only to the physician interested principally in electrotherapy, but to any one who wishes a thorough knowledge of the field of radiant energy.