Note 3 — Chapter V · ON THE EXISTENCE OR NON-EXISTENCE OF A LUNAR ATMOSPHERE.
Reading edition
Irradiation is an ocular phenomenon in virtue of which all strongly illuminated objects appear to the eye to be larger than they really are. The impression produced by light upon the retina appears to extend itself around the focal image formed by the lenses of the eye. It is from the effect of irradiation that a white disc on a black ground looks larger than a black disc of the same size on a white ground.