28 Sir David Brewster on a Binocular Camera, §c. 



If we now suppose the building or statue to be reduced in the 

 most perfect manner, — to half its size, for example, — then it is ob- 

 vious that these two perfectly similar solids will afford a different 

 picture, whether viewed by the eye or by the telescope. In the 

 reduced eopv, the inner surfaces visible in the original will dis- 

 appear, and the outer surfaces become visible ; and, as formerly, 

 it will depend on the nature of the building or the statue whether 

 the reduced or the original copy gives the best picture. 



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 only one- half the illumination of the rest 

 of the picture. But, though we see more of the body in bin- 

 ocular 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 eve. 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 2i inches in diameter, to enable us to have a 

 perfectly symmetrical view of the statue. 



These observations will enable us to answer the question, 

 wdiether or not a reduced copy of a statue, of precisely the same 

 form in all its parts, will give us, either by monocular or bin- 

 ocular 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 2i inches, we shall not 

 see a complete hemisphere unless from an infinite distance. If 

 the sphere is 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 ob- 

 vious 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. 



With these observations, we shall be able to determine the 

 best method of obtaining dissimilar plane drawings of full-length 

 and colossal statues, &c, in order to reproduce them in three 

 dimensions by means of the stereoscope. Were a painter called 

 upon to take drawings of a statue, as seen by each eye, he would 



