A LECTURE on the “Photographic Analysis of Motion” was delivered at the Royal Institution on December 11 by Mr. E. R. Davies, director of research, Messrs. Kodak, Ltd. He said that the value of photography in the analysis of movements too rapid for the eye to follow was demonstrated, and the method successfully applied, in the classical investigations of Muybridge and Marey before the introduction of the dry plate in 1871. The great convenience of the new process compared with the laborious wet-plate technique, and its enhanced sensitivity, brought about many triumphs towards the end of the nineteenth century. The movements of animals and the flight of birds were analysed ; projectiles travelling at speeds in excess of that of sound photographed ; and the propagation of flames in gaseous combustion was followed. Modern progress had depended to a large extent upon the introduction of the cold cathode discharge tube in place of the far less luminous electric spark ; on advances in the design of cinematographic and other types of camera ; on the introduction of photographic materials of greatly increased sensitivity ; and on the application of the photo-electric cell and the microphone to the problem of synchronizing the action with the camera exposure. Instantaneous photographs can now be taken with exposures of less than a millionth of a second and cinematograph pictures with a frequency in excess of 4,000 a second. A valuable tool has become available to science and industry, and has proved its worth in many fields. Its use in the design and testing of high-speed machinery is of particular importance at the present time.