Some Observations on the Rotating Pendulum

Abstract

THE observations by Lythgoe¹ on the ‘rotating pendulum’ are almost entirely in accord with the hypothesis that the ‘latent period’ of vision varies in the same sense as the concentration of photochemical substance in the retina of the eye, and is controlled mainly, if not entirely, by this concentration. The concentration of photochemical substance is decreased (a) by a general increase in illumination of the field of view ; (b) by the contemporaneous presence of one or more glare sources in the field of view; (c) by the previous presence of glare sources in the field of view. In case (c), of course, the concentration of photochemical substance is steadily returning to its equilibrium value in the absence of glare sources.