In a Flash of Light

The belief that the human eye sometimes shines with an internal fire of its own, is based upon fact. One of the most interesting experiments ever tried by that exceedingly interesting man, Prof. Helmholtz, related to this question of the luminosity of the eye. Going into a room that was totally dark he was actually able to see his arm by means of the light issuing from the retina of his own eyes. The success of this remarkable experiment has been ascribed to the intense activity of the experimenter’s brain. In referring to this strange incident, Nikola Tesla remarked that probably only a few men could satisfactorily repeat it, as the light seen was a sort of “fluorescence of brain action” produced by the activity of a mind of very uncommon power. Mr. Tesla, at the same time, recalled the fact that a flash of light is sometimes perceived when an image suddenly presents itself to the intellect. Thus it sometimes happens that scientific investigation not only confirms old popular notions, apparently of fanciful origin, but also makes them appear even more wonderful than before.