on the rectangle’s sides.
Any number of points in the curve may be thus determined, and the curve drawn through the series; in most cases, three or four will be enough. Practically, complicated curves may be better drawn in perspective by an experienced eye than by rule, as the fixing of the various points in haste involves too many chances of error; but it is well to draw a good many by rule first, in order to give the eye its experience.[Footnote 22] ]
COROLLARY.
If the curve required be a circle, [Fig. 30.], the rectangle which incloses it will become a square, and the curve will have four points of contact, A B C D, in the middle of the sides of the square.
Fig. 30.
Draw the square, and as a square may be drawn about a circle in any position, draw it with its nearest side, E G, parallel to the sight-line.
Let E F, [Fig. 31.], be the square so drawn.
[p40]
]Draw its diagonals E F, G H; and through the center of the square (determined by their intersection) draw A B to the vanishing-point of G F, and C D parallel to E G. Then the points A B C D are the four points of the circle’s contact.
