There is probably no construction in geometry which is so readily acceptable as that of drawing the straight line. Although Euclid postulated this construction in 300 B.C., it was not until over 2000 years had elapsed that a mechanical device was invented for making the construction. Euclidian geometry is based upon two fundamental postulates: first, that it is possible to draw a straight line between two points, second, that a circle can be drawn with any point as center and any line as radius. The second construction (postulate 3) is easy to make. Take any object, however irregular its shape, preferably fiat but not necessarily so; choose any point on its surface, such as A, and thereafter cause that point to remain fixed at the required center in the plane. Choose another point B at the required distance from the first; cause the second point to move freely about the first, and the locus described by it will be a circle with A as center and AB as radius. (See figure 1.)