Ruskin, John; Cook, Edward T. [Editor]: The works of John Ruskin: The elements of drawing. The elements of perspective. And the laws of Fésole (London, 1904)

280 THE ELEMENTS OF PERSPECTIVE

the points A B c D are the four points of the circles
contact.
On E & describe a half square, E L; draw the semicircle
K A L; and from its centre, R, the diagonals R E, R G, cutting
the circle in a?, p.
From the points a? p, where the circle cuts the diagonals,
raise perpendiculars, a? p, ?/ Q, to E G.
From p and Q draw p p', Q Q', to the vanishing-point of
G F, cutting the diagonals in ??&, and
o, jp.
Then 77^, 7a, o, p are four other points
in the circle.
Through these eight points the circle
may be drawn by the hand accurately
enough for general purposes; but any
number of points required may, of course,
be determined, as in Problem XI.
The distance E p is approximately
one seventh of E G, and may be assumed to be so in quick
practice, as the error involved is not greater than would be

B


HP' B Q' F


incurred in the hasty operation of drawing the circle and
diagonals.
It may frequently happen that, in consequence of associated