is the line required.
[p14]
][COROLLARY I.]
If the line A B is in a plane parallel to that of the picture, one end of the line A B must be at the same direct distance from the eye of the observer as the other.
Therefore, in that case, D T is equal to D′ T.
Then the construction will be as in [Fig. 7.]; and the student will find experimentally that
a b
is now parallel to A B.[Footnote 11] ]
Fig. 7.
And that