the two. We invite the reader to call to mind the following facts as bearing on our present view.
250.
Grey objects appear lighter on a black than on a white ground (33); they appear as a light on a black ground, and larger; as a dark on the white ground, and smaller. (16.)
251.
The darker the grey the more it appears as a faint light on black, as a strong dark on white, and vice versâ; hence the accessory images of dark-grey on black are faint, on white strong: so the accessory images of light-grey on white are faint, on black strong.
252.
Grey on black, seen through the prism, will exhibit the same appearances as white on black; the edges are coloured according to