JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. IV AUGUST 19, 1914 No. 14 



PHYSICS. — The axial chromatic aberration of the human eye. 

 P. G. Nutting, Eastman Research Laboratory, Rochester, 

 N. Y. 



A bright object viewed directly by a normal human eye shows 

 no perceptible colored fringes. From this it has been assmiied by 

 some that the eye is fairly well corrected chromatically — at least 

 for the most luminous constituents of white Ught. On the other 

 hand, if the same object be viewed through a filter transmitting 

 only the extreme red and blue, it will appear with either a red or 

 blue fringe, showing that for these extreme rays the eye is not 

 corrected. 



Helmholtz^ passed monochromatic light through a small hole 

 and found that when red light was used the hole appeared in best 

 focus when viewed from a distance of about 8 feet. With blue 

 illumination it appeared brightest at about 1^ feet, and with 

 extreme violet but a few inches (nur einige Zolle). With these 

 rough determinations of Helmholtz the question appears to have 

 rested. 



With the aid of very simple apparatus it was found possible to 

 obtain rather precise determinations of axial focal length. The 

 test object used was the image of the slit of a monochromatic 

 illuminator (*S, fig. 1) formed by a movable lens L of about 20 

 cm. focal length. At a fixed distance (about 20 cm.) back of this 

 was the observer's eye, E. In order to fix the accommodation 



iPhysiolog. Optik, 3rd edition, 1: 147. 1909. 



385 



