9/26 The full treatment of this subject would form a chapter in itself; here I can only touch on its main features. Yet it manages to produce a pretty strong illusion. It illustrates in a striking manner the ease with which the eye conceives relations of depth or relief and solidity. If, for example, on a carpet, wall-paper, or dress, bright lines are laid on a dark colour as ground, we easily imagine that they are advancing. The reason of this seems to be that in our daily experience advancing surfaces catch and reflect the light, whereas retiring surfaces are in shadow.[38] The same principle is illustrated in one of the means used by the artist to produce a strong sense of relief, namely, the cast shadow. |