There is much more to be said about the chain of circles that can be inscribed into an Archimedes' arbelos (shoemaker's knife), but just getting the construction done is a challenge. Further study could investigate the relation between the diameter of each of the circles in the chain and the distance from the centre of each circle to the base line of the arbelos ([i]distance[/i] = [i]n[/i] * [i]diameter[/i], where [i]n[/i] is the number of the circle in the chain).