Factors which determine the Occurrence of the Green Ray

Abstract

THE recent discussion of the green ray which has been appearing in NATURE prompts me to put on record a new theory of the phenomenon which occurred to me several years ago, but which I have refrained from publishing in the hope of securing proof. First let me say most emphatically that the phenomenon is real and not an illusion or after-image. No person trained in the observation of optical effects, both real and subjective, who has seen the phenomenon at its best, will have any doubt about its reality. There is also no question in my mind but that the usual explanation (atmospheric dispersion) is quite correct. The main question to answer is, Why is it seen so seldom, even under conditions which appear to be the most favourable ?