258 O.N. Rood on Combination of Light of different tints, 
pression a neutral one, when the method by rotation shows that — 
this is not truly the case. This is illustrated in a striking man- 
an experiment previously published by me, which] haye 
lately repeated a number of times with the same result. A yel- 
low glass is held before one of the eyes, a blue glass before the 
other, when, as Briicke rightly states, a landscape thus viewed, — 
seems of a neutral gray if the attention be equally directed to 
the two impressions. When, however, the two glasses are 
tached to opposite openings in a blackened card dise, and set in 
rapid rotation so that the tints are truly mixed and a true result 
ant obtained, this is found (with the glasses I employed), to bea 
_ strong purple, though nothing of this kind is seen or sugg 
in the binocular use of the glasses. It is probably this tendency 
to consider the resultant neutral, that makes it so easy to com 
bine, in binocular vision, tints produced by polarized light, and 
to perceive that the resultant is white. : 
t may be remarked in passing, that when the stereoscope 8 
held as  poaca before the two halves of the colored dise, and ee 
the latter is caused to revolve slowly, that the aperture in the 
card board appears extraordinarily lustrous, so much so that 1b 
would be possible by a little artistic arrangement of the access 
ries to deceive persons with the belief that they were looking # 
the surface of a polished metallic mirror. 
Binocular union of complementary tints produced by polarized light. : | 
For the purpose of experimenting on this point, I arranged + : 
m 
late of polish 
. 
in blac 
employed on account of the rapid change of the tint b 
inclination. As the colors were exactly complementary, 
sultant by binocular vision should always be pure W ite. 
card board. Films of common mica cannot We 
Results with polarized light. 
readiness to make a white. The same was true of i 
the 8rd order; here the resultant white was very easily © 
order, gave a good result. The same tints o 
readily neutralized each other. 
* 
Senay ieee Sp Resi aes 
nero’ Sus 
objects, plates of selenite were used, fastened behind apertures 
black eo 
y the least a 
Ast, Red with greenish blue of 2nd order combined wae SS 
