the diagrams in the original have no connection with the text.]
255.
If several luminous bodies are seen from a great distance although they are really separate they will appear united as one body.
256.
If several objects in shadow, standing very close together, are seen against a bright background they will appear separated by wide intervals.
257.
Of several bodies of equal size and tone, that which is farthest will appear the lightest and smallest.
258.
Of several objects equal in size, brightness of background and length that which has the flattest surface will look the largest. A bar of iron equally thick throughout and of which half is red hot, affords an example, for the red hot part looks thicker than the rest.
259.
Of several bodies of equal size and length, and alike in form and in depth of shade, that will