on his own subject; in this book the reader will not be disappointed. Moreover, the translation from the original French, with the inclusion of some new material, suffers from few of the defects so frequently seen, for it reads fluently and spontaneously as if it were the original text. The first chapter deals with the nature of light and its relation to other forms of radiant energy: a succinct and interesting review, followed by a full description of different types of illuminants including the various types of artificial lighting and natural lighting from the sun. This is followed by a description of the physiology of vision and the functioning of the eye shown by experiments carried out on the human eye by physical methods. This part comprises a full discussion of such problems as photometry, the illumination of the retina, luminance efficiency and the duality of the retina, colorimetry and the trivariance of the retina, colour vision and its anomalies, and the various thresholds, time effects, and the spatial interactions affecting vision. The second section of the book is more physiological and speculative. It is introduced by a description of the relevant anatomy of the eye, the photochemistry and electrophysiology of vision, the various theories of colour vision, and a physiological interpretation of the visual thresholds. The book is easy and good to read and gives a fair and critical exposition of its subject. It should be useful not only to the ophthalmologist but also to the physiologist and physicist.