The Action Of The Eye

Saturday, October 28, 1893
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The Action of the Eye# NTKOLA TESLA. It can be taken as afact, which the theory of the action of the eye implies, that for each external im- pression, that is, for each image produced on the retina, the ends of the visual nerves concerned in the convey- ance of the impression to the mind must he under a peculiar stress or in a vibratory state. It now does not seem improbable that, when by the power of thought an image is evoked, a distant retlex action, no matter how weak, i.s exerted upon certain ends of the visual nerves, and, therefore, upon the retina. Will it ever be within human power to analyze the condition of the retina when disturbed by thought or rellex action, by the help of some optical or other means of such sensi- tiveness that a clear idea of its state might be gained at any time Y If this were possible, then the problem of reading onels thoughts with precision, like the characters of an open book, might be much easier to solve than many problems belonging to the domain of positive physical science, in the solution of which many if not the majority of scientific men implicitly believe. Helmholtz has shown that the fundi of the eyes are themselves luminous, and he was able to see, in total darkness, the movement of his arm by the light of his own eyes. This is one of the most remark- able experiments recorded in the history of science, and probably only a few men could satisfactorily re- peat it, for it is very likely that the luminosity of the eyes is associated with uncommon activity of the brain and great imaginative power. It is Huorescence of brain action, as it were. Another fact having a bearing on this subject which has probably been noted by many, since it is stated in popular expressions, but which I cannot recollect to have found chronicled as a positive result of observa- tion, is that at times, when a sudden idea or image presents itself to the intellect, there is a distinct and sometimes painful sensation ot' luminosity produced in the eye, observable even in broad daylight. Two facts about the eye must forcibly impress the mind of the physicist, notwithstanding he may think or say that it is an imperfect optical instrument, for- getting that the very conception of that which is per- fect, or seems so to him, has been gained through this same instrument. First, the eye is, as far as our positive knowledge goes, the only organ which is directly affected by that subtile medium which, as science teaches us, must till all space; secondly, it is _ ‘Extract from paper on the “Action of tho Eye," rand before Franklin Institute. OCTOBER 14, l8Q3.;| 245 the most sensitive of our organs, incomparably more sensitive to external impressions than any other. This divine organ of sight, this indispensable instru- ment for thought and all intellectual enjoyment, which lays open to ns the marvels of this universev through which we have acquired what knowledge we possess, and which prompts us to and controls all our physical and mental activity-by what is it affected ? By lightl What is light? It is beyond the scope of my lecture to dwell upon the subject of light in general, my object being merely to bring presently to your notice a certain class of light effects and a number of phenomena observed in pursuing the study of these effects. But to he consis- tent in my remarks it is necessary to state that accord- ing to the idea now accepted by the majority of .scien- tific men as a positive result of theoretical and experi- mental investigation. the various forms of nmnifesta- tion of energy which were generally designated as “electric," or more precisely “electro-magnetic." are energy manifestations of the same nature as those of radiant heat and light. Therefore the phenomena of light and heat, and others besides these, may be called electrical phenomena. Thus electrical science has be- come the mother science of all, and its study has be- come all-important. The day when we shall know exactly what “electricity " is, will chronicle an event probably greater and more important than any other recorded in the history of the human race.