Construction Of A Parabola
An illustration showing how to construct a parabola. "Given the axis of ordinate B, and vertex A. Take A as a center and describe a semicircle from B which gives the focus of the parabola at f. Draw any ordinate y at right angle to the abscissa Ax, take a as radius and the focus f as a center, then intersect the ordinate y, by a circle-arc in P which will be a point in the parabola. In the same manner the whole Parabola is constructed."
Albert A. Hopkins Scientific America: Handy Book Of Facts And Formulas (New York: Munn & Co., Inc., 1918) 39
Courtesy the private collection of Roy Winkelman