If you look at a luminous body in the far distance through a smallhole it will seem to grow less, and if you look at it near at hand it will not undergo any change. That is that if you look at this light atadistance of one or two braccia from the aforesaid hole it will not undergo any change whether you are looking at it through this hole or outside of it.

Every body that moves rapidly seems to colour its path with the impression of its hue. The truth of this proposition is seen from experi-ence; thus when the lightning moves among dark clouds the speedofits sinuous flight makes its whole course resemble a luminous snake.So in like manner if you wave a lighted brand its whole course will seem a ring of flame. This is because the organ of perception acts more rapidly than the judgment.

Light is the chaser away of darkness. Shade is the obstruction of light. Primary light is that which falls on objects and causes light and shade. And derived lights are those portions of a body which are illuminated by the primary light. A primary shadow is that side of a body on which the light cannot fall.

All bodies together, and each by itself, give off to the surrounding air an infinite number of images which are all-pervading and each complete, each conveying the nature, colour and form of the body which produces it.

The eye which finds itself in the centre between the shadows and the lights that surround the shaded bodies, will see in these bodies thegreater shadows that are in them meeting themselves within equal angles that is of the visual incidence.

The eye transmits its own image through the air to all the objects which face it, and also receives them on its own surface, whence the "sensus communis" takes them and considers them.