Chapter 2 HOW TO DRAW A STRAIGHT LINE The straight line is a stronger and more profound expression than the curve. Piet Mondrian This chapter heading comes from a book by A. B. Kempe, How to Draw a Straight Line: A Lecture on Linkages (Kempe 1877). The charm and gentle tone of the book suggest that the origi- nal lectures must have been a delightful experience. If you ask most people what a straight line is their answer will probably involve `the shortest distance between two points'. Of course they do not always mean this since the shortest distance to the Antipodes from Yorkshire is downwards through the centre of