The late Rev. Dr. Scoresby explained with much minuteness and skill
the varying phenomena which presented themselves to him after gazing
intently for some time on strongly-illuminated objects,--as the sun,
the moon, a red or orange or yellow wafer on a strongly-contrasted
ground, or a dark object seen in a bright field. The doctor explained,
upon removing the eyes from the object, the early appearance of the
picture or image which had been thus “photographed on the Retina,” with
the photochromatic changes which the picture underwent while it still
retained its general form and most strongly-marked features; also, how
these pictures, when they had almost faded away, could at pleasure, and
for a considerable time, be renewed by rapidly opening and shutting the
eyes.