All the minutest parts of the image intersect each other without interfering with each other. To prove this let _r_ be one of the sides of the hole, opposite to which let _s_ be the eye which sees the lower end _o_ of the line _n o_. The other extremity cannot transmit its image to the eye _s_ as it has to strike the end _r_ and it is the same with regard to _m_ at the middle of the line. The case is the same with the upper extremity _n_ and the eye _u_. And if the end _n_ is red the eye _u_ on that side of the holes will not see the green colour of _o_, but only the red of _n_ according to the 7th of this where it is said: Every form projects images from itself by the shortest line, which necessarily is a straight line, &c. [Footnote: 13. This probably refers to the diagram given under No. 66.] 271. OF PAINTING. The surface of a body assumes in some degree the hue of those around it. The colours of illuminated objects are reflected from the surfaces of one to the other in various spots, according to the various positions of those objects. Let _o_ be a blue object in full light, facing all by itself the space _b c_ on the white sphere _a b e d e f_, and it will give it a blue tinge, _m_ is a yellow body reflected onto the space _a b_ at the same time as _o_ the blue body, and they give it a green colour (by the 2nd [proposition] of this which shows that blue and yellow make a beautiful green &c.) And the rest will be set forth in the Book on Painting. In that Book it will be shown, that, by transmitting the images of objects and the colours of bodies illuminated by sunlight through a small round perforation and into a dark chamber onto a plane surface, which itself is quite white, &c. But every thing will be upside down. Combination of different colours in cast shadows. 272. That which casts the shadow does not face it, because the shadows are produced by the light which causes and surrounds the shadows. The shadow caused by the light _e_, which is yellow, has a blue tinge, because the shadow of the body _a_ is cast upon the pavement at _b_, where the blue light falls; and the shadow produced by the light _d_, which is blue, will be yellow at _c_, because the yellow light falls there and the surrounding background to these shadows _b c_ will, besides its natural colour, assume a hue compounded of yellow and blue, because it is lighted by the yellow light and by the blue light both at once. Shadows of various colours, as affected by the lights falling on them. That light which causes the shadow does not face it. [Footnote: In the original diagram we find in the circle _e_ "_giallo_" (yellow) and the cirle _d_ "_azurro"_ (blue) and also under the circle of shadow to the left "_giallo_" is written and under that to the right "_azurro_". In the second diagram where four circles are placed in a row we find written, beginning at the left hand, "_giallo_" (yellow), "_azurro_" (blue), "_verde_" (green), "_rosso_" (red).]