Appleton's cyclopædia of drawing, designed as a textbook for the mechanic, architect, engineer, and surveyor (1866)
Worthen, William Ezra, 1819-1897, [from old catalog] ed, Appleton, firm, publishers, New York. (1866. D. Appleton & co.) [from old catalog] · New York, D. Appleton and company · leaf 96
the other focus F by a cord shorter than thewliolc hlio-lh V \X of the ruler by the given difference ; then a pencil Pkeci)ing tliis cord always stretched, and at tlie same time pressing againstthe edge of the ruler, will, as the ruler revolves around F, describe anliyperbohi, of which F F arc the… … On r P lay off P^ equal to F P ; connect F^;>, and from P let fall apeiiDendicnlar on this line F^;>, andit will be the tangent required. The three curves, the ellipse,the parabola, and the hyperbola,are called conic sections, as theyare formed by the intersections of aplane with the surface…
