{ 
£.. L. Nichols—Color Impressions upon the Retina. 249 
would be much flattened, at any rate toward the violet, and its 
values would be more nearly in inverse proportion to the dura- 
tion of the retinal images, in series A, B, and C, 
To determine whether the general form of the curve for the 
duration of color-impressions was the same for all eyes, Mr. 
Wilson Sterne, of Texas, who had been assisting the writer in 
the measurements already described, made the following set of 
readings. The conditions were the same as those under which 
series B had been obtained. As may be seen from the follow- 
ing table and from the corresponding curve (D), the variations 
in the duration of the image upon Mr. Sterne’s retina are very 
different from those represented in series A, B, and C. he 
impression of yellow lasts longer, while the green and blue 
images fade more rapidly. These measurements were repeated 
many times, the curve always taking the general form shown 
in carve D. 
Series D. , 
Conditions, those of Series B; Wilson Sterne observing. 
ions ~ Interval between Duration of 
Spectral region. per minute. exposures of retina. exposure, 
_ 7420 (red 176 0°0831 seconds. 0°00226 seconds. 
- 6463 (orange 214 0683  ¥ OGERG © 6 Sc, 
6025 tyelleey} 238 ROL a 000167 
5415 (green) 224 00653... * 000178 = * 
4724 rin 190 OTTO 000210 == * 
4382 violet) 148 0°0988 0:00270 % 
of the variation. Perhaps unusual sensitiveness of the eye to 
certain portions of the spectrum may lessen the duration of the 
Corresponding color-impressions, just as the increased brightness 
of the ray itself is known to do. If this be true, the phenome- 
hon stands closely related to color-blindness; the precise nature 
the ray producing them; but that it depends, like color itself, 
wholly upon the character of the nerves affected. When the 
in the violet, the image of the yellow and green portions disap- 
peared first, leaving behind it a dark violet band extending the 
