If we repeat the preceding experiments with _two eyes_ in place of _one_, the building or statue will have a different appearance; surfaces and parts, formerly invisible, will become visible, and the body will be better seen because we see more of it; but then the parts thus brought into view being seen, generally speaking, with one eye, will have less brightness than the rest of the picture. But though we see more of the body in binocular vision, it is only parts of vertical surfaces perpendicular to the line joining the eyes that are thus brought into view, the parts of similar horizontal surfaces remaining invisible as with one eye. It would require a pair of eyes placed vertically, that is, with the line joining them in a vertical direction, to enable us to see the horizontal as well as the vertical surfaces; and it would require a pair of eyes inclined at all possible angles, that is, a ring of eyes 2½ inches in diameter, to enable us to have a perfectly symmetrical view of the statue. These observations will enable us to answer the question, whether or not a reduced copy of a statue, of precisely the same form in all its parts, will give us, either by monocular or binocular vision, a better view of it as a work of art. As it is the outer parts or surfaces of a large statue that are invisible, its great outline and largest parts must be best seen in the reduced copy; and consequently its relief, or third dimension in space, must be much greater in the reduced copy. This will be better understood if we suppose a _sphere_ to be substituted for the statue. If the sphere exceeds in diameter the distance between the pupils of the right and left eye, or 2½ inches, we shall not see a complete hemisphere, unless from an infinite distance. If the sphere is very much larger, we shall see only a segment, whose relief, in place of being equal to the radius of the sphere, is equal only to the versed sine of half the visible segment. Hence it is obvious that a reduced copy of a statue is not only better seen from more of its parts being visible, but is also seen in stronger relief. _On the Proper Position of the Sitter._ With these observations we are now prepared to explain the proper method of taking binocular portraits for the stereoscope.