As relaxation from his political and religious polemics, Napier amused himself with the study of mathematics and science, with the result that four products of his genius are now recorded in the history of mathematics. These are (1) the invention of logarithms; (2) a clever mnemonic, known as the rule of circular parts, for reproducing the formulas used in solving right spherical triangles; (3) at least two trigonometric formulas of a group of four known as Napier's analogies, useful in the solution of oblique spherical triangles; and, (4) the invention of a device, called Napier's rods, or Napier's bones, used for mechanically multiplying, dividing, and taking square roots of numbers. We turn now to the first, and most remarkable, of these four contribution; for a discussion of the other three, see problem Studies 9.2