On light-sensations and the theory of forced vibrations

Every hypothesis, whether mechanical, photo-chemical, or ionic, concerning the connection between the light-waves and the sensations they evoke, must of necessity rest ultimately on the theory of forced vibrations. It seemed probable, therefore, that a model illustrating the production of forced vibrations over a range comparable with that of a light-sensation might be of service for teaching purposes, and might prove suggestive in studying the phenomena of vision. The apparatus now described was made for me in May, 1909, by Mr. H. Davis, the Assistant for Manual Instruction at University College, Reading, and was used in my lectures both in Reading and in Oxford, but no account of it has been published. From a light wooden bar, A (fig. 1), pivoted at the two ends, bang a number of grey silk ribbons, varying in length from 11 to 44 cm. The longest, which represent the red end of the spectrum, have therefore a period twice as long as that of the shortest, which correspond to violet. Each ribbon is weighted at the end with a strip of lead.