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

to cut the line of sight in N.

Fig. 14.

Then as X R′ is parallel to M N, and

a

R′ is equal to

a

X, V N must, by similar triangles, be equal to V M (equal to V T in [Fig. 13.]).

Therefore, on whichever side of V we measure the distance V T, so as to obtain either the point M, or the point N, if we measure the sight-magnitude

a