Join the extremities a and b (Fig. 191), and from f, the given projection of the moulding, draw/0 at right angles to the fillets; from b draw bh at right angles to a b; bisect a b in c; join f and c, and upon c, with the radius cf, describe the arc fh, cutting bh in h; through c draw de parallel with the fillets; make dc and ce each equal to bh; then de and a b will be conjugate diameters of the required ellipse. To describe the curve by intersection of lines, proceed as directed at Art.

Fig. 194.

Fig. 195.

The Grecian Echinus

551 and note; by a trammel, see Art. 549; and to find the foci, in order to describe it with a string, see Art. 548.