THE Council of the Physical Society has awarded the fourteenth Duddell Medal to Walter G. Cady, professor of physics at the Wesleyan University, Middletown, Connecticut, U.S.A., for his work on piezo-electric resonators and oscillators as standards of frequency. Prof. Cady's pioneer work on the subject was published in 1922 (Proc. Inst. Radio Eng., 10, 83) and the value of the device may be judged from the fact that it stimulated research work on the subject in all parts of the world, more than a thousand papers having been published on the properties of piezo-eleotric crystals since the appearance of Cady's first paper. Of course, these are not all due to Cady's work, for Langevin had previously used piezo-electric crystals as vibrators for underwater signalling, but Cady's particular contribution- the use of the quartz resonator as a standard of time or frequency-has quite obviously inspired most of the work. The use of these resonators as standard vibrators has made it possible to measure frequency and intervals of time with an accuracy not previously attained. It is scarcely necessary to emphasize the importance to physics of increased accuracy in such fundamental measurements. Among the applications which have already been made the following may be mentioned: (1) The quartz-clock now used as standard in some observatories. It is in some respects superior to the pendulum clocks, and in any event is a most valuable supplement to them. (2) The measurement and control of the frequency of alternating currents in connexion with measurements of dielectric constant, 'absolute' electrical measurements, etc. (3) The measurement of the velocity of ultrasonic sound waves. Duddell, who was responsible for so much elegant instrumental work, would have been the first to recognize the beauty of Prof. Cady's device, and it will be a source of great satisfaction to all scientific workers to know that the value of Prof. Cady's work has been recognized in such an appropriate manner.