Book I: discusses construction of certain geometric figures using instruments, compares basic elements of geometry to basic operations in arithmetic; Book II: proves that the set of curved figures described by the range of 3rd order equations is limited to the known set of surfaces (circle, ellipse, hyperbola, parabola); also makes references to his own Dioptrique; Book III: "But it is not my purpose to write a large book. I am trying rather to include much in a few words.... I hope that posterity will judge me kindly, not only as to the things which I have explained, but also as to those which I have intentionally omitted so as to leave others the pleasure of discovery." ( )