EYES. 



By W. E. Watt. 



Why was the sight 

 To such a tender ball as th' eye confined, 

 So obvious and so easy to be quenched, 

 And not, as feeling, through all parts diffused; 

 That she might look at will through every pore ? — M11.TON. 



But bein' only eyes, you see, my wision's limited." — Sam WellER. 



HE REASON we know any- 

 M thing at all is that various 



(J forms of vibration are capa- 



ble of affecting our organs 

 of sense. These agitate the brain, the 

 mind perceives, and from perception 



arise the 

 Perhaps the 



higher 



forms of thought, 

 most important of the 

 senses is sight. It ranges in power 

 from the mere ability to perceive the 

 difference between light and darkness 

 up to a marvelous means of knowing 

 the nature of objects of various forms 

 and sizes, at both near and remote 

 range. 



One the simplest forms of eyes is 

 found in the Sea-anemone. It has a 

 colored mass of pigment cells and 

 refractive bodies that break up the 

 light which falls upon them, and 

 it is able to know day and night. An 

 examination of this simple organ leads 

 one to think the scientist not far wrong 

 who claimed that the eye is a develop- 

 ment from what was was once merely 

 a particular sore spot that was sensitive 

 to the action of light. The protophyte, 

 Eiiglena varidis^ has what seems to be 

 the least complicated of all sense 

 organs in the transparent spot in the 

 front of its body. 



We know that rays of light have 

 power to alter the color of certain 

 substances. The retina of the eye is 

 changed in color by exposure to con- 

 tinued rays of light. Frogs in whose 

 eyes the color of the retina has 



apparently been all changed by sun- 

 shine are still able to take a fly accu- 

 rately and to recognize certain colors 



Whether the changes produced by 

 light upon the retina are all chemical 

 or all physical or partly both remains 

 open to discussion. 



An interesting experiment was per- 

 formed by Professor Tyndall provin.^ 

 that heat rays do not affect the eye 

 optically. He was operating along 

 the line of testing the power of the 

 eye to transmit to the sensorium the 

 presence of certain forms of radiant 

 energy. It is well known that certain 

 waves are unnoticed by the eye but 

 are registered distinctly by the photo- 

 graphic plate, and he first showed 

 beyond doubt that heat waves as such 

 have no effect upon the retina. By 

 separating the light and heat rays from 

 an electric lantern and focusing the 

 latter, he brought their combined 

 energy to play where his own eye 

 could be placed directly in contact 

 with them, first protecting the exterior 

 of his eye from the heat rays. There 

 was no sensation whatever as a result, 

 but when, directly afterward, he 

 placed a sheet of platinum at the 

 convergence of the dark rays it quickly 

 became red hot with the energy whicli 

 his eye was unable to recognize. 



The eye is a camera obscura with a 

 very imperfect lens and a receiving 

 plate irregularly sensitized; but it has 

 marvelous powers of quick adjust 



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