Tait worked across boundaries, and is especially known for his work on the mathematics of knots and a book written with Thomson. He and his friend from schooldays on, Maxwell, lived intertwined lives, with their friend Thomson often a third strand. Dewar was another collaborator. Hamilton, correspondent and friend, was an important influence. Inclined to let heart rule head, Tait got into unwinnable arguments with Cayley, Tyndall, Heaviside and (in print) Clausius. He played golf with Helmholtz (baffled by it), and with Huxley and Crum Brown (whose hand got burned by their phosphorescent night-time ball).