Let a b be the transverse or longest diameter ; c d the conjugate or shortest diameter; and o the point of their intersection, that is, the centre of the ellipse. Take the distance O C or O D; and, taking A as one point, mark that distance a e upon the line a o. Divide O E into three equul parts, and take from a f, a distance E F, equal to one of those parts. Make O G equul to O F. With the radius F G and F and G as centres, strike arcs which shall intersect each other in the points I and H. Then draw the lines H f k, h G m, and I F L, I G N. With F as a centre, and the radius A F, describe the arc l a k ; and, from G as a centre. with the same radius, describe the arc m b n. With the radius H C, and h as a centre, describe the arc k c m; and, from the point I, with the radius I d, describe the arc l d m. The figure a c b d is an ellipse, formed of four arcs of circles.

Fig. 36.