In 1646 the 17-year-old Christiaan Huygens proved that the hanging chain did not take the shape of a parabola, as was commonly thought at the time. Forty-four years later, no one had yet described the actual shape of the chain, so Jakob Bernoulli posed the problem publicly in 1690. Huygens then studied several aspects of this curve, which he called the catenary, and published them in a short article one year later. We will quickly review the earlier work of Huygens and concentrate on the work from his notebooks in 1691.

This talk is a continuation of the story begun at PASHoM in April 2009, although attendance at that talk is not a prerequisite for this one.