Note 22 — Chapter IV
Reading edition
The perception of lustre as a single quality seems to illustrate a like error. There is good reason to suppose that this impression arises through, a difference of brightness in the two retinal images due to the regularly reflected light. And so when this inequality of retinal impression is imitated, as it may easily be by combining a black and a white surface in a stereoscope, we imagine that we are looking at one lustrous surface. (See Helmholtz, Physiologische Optik, p. 782, etc., and Populäre wissenschaftliche Vorträge, 2tes Heft, p. 80.)