The Elements of Perspective / arranged for the use of schools and intended to be read in connection with the first three books of Euclid

by John Ruskin

a c

, drawn in position, as in [Fig. 21.]

Fig. 21.

And because A B C D is a square, C D ([Fig. 20.]) is parallel to A B.

And all parallel lines have the same vanishing-point. (Note to [Problem III.])

Therefore, V is the vanishing-point of C D.

Similarly, V′ is the vanishing-point of B D.

Therefore, from

b