Page:A Treatise on Painting.djvu/348

 and B C. I say, that the sides of the visual angles (which contain these central rays) will see the space G D, behind the object C. The eye A will see all



the space FD, and the eye B all the space G E. Therefore the two eyes will see behind the object C all the space F E; for which reason that object C becomes as it were transparent, according to the definition of transparent bodies, behind which nothing is hidden. This cannot happen if an object were seen with one eye only, provided it be larger than the eye. From all that has been said, we may conclude, that a painted object, occupying all the space it has behind, leaves no possible way to see any part of the ground, which it covers entirely by its own circumference. Rh