J. LeConte on Binocular Vision. 5 
is not possible, to bring out the inverse perspective distinctly. — 
he reason is that it violates other kinds of perspective, and 
sometimes sets at defiance the known properties of bodies. It 
is most distinct when other kinds of perspective are least dis- 
tinct. In natural vision there are many kinds of perspective, 
or many modes of judging of the relative distance of objects ; 
viz. aertal perspective or increasing dimness with increasing dis- 
tance; mathematical perspective or decreasing size with increas- 
ing distance; change of focal adjustment necessary for distinct 
vision of near and distant objects; change of axial adjust- 
ment necessary for s’ngle vision of near and distant objects. 
The first three of these are monocular, the last is binocular. The 
painter can give only the first two. The stereoscope gives also 
the last, and its surprising effects are due to this cause. In 
natural vision alone all kinds concur. Now in reversing the 
binocular perspective we do not affect the other kinds. ere 
is therefore, a discordance between this and the other kinds, and 
when they exist it must overpower them. This it cannot do 
when the mathematical perspective is strongly marked. us 
the curious effects of inverse perspective is best seen when the 
other forms of perspective, particularly the mathematical, are 
least marked. It is impossible to see it in cases of long build- 
ings or long rows of buildings taken in perspective. In such 
cases the mathematical overpowers the binocular perspective. 
But in buildings and grounds seen directly in front it is very 
evident. I now combine with the naked eye stereoscopic 
