The problem of designing cams or centrodes to produce any given motion in one plane is one of some practical importance; and it seems worth while to illustrate by examples some simple methods by which the solution can in certain cases be arrived at. These methods are founded, for the most part, on the use of the so-called Pedal Equation (or p-r-equation), which has great advantages in the present investigation, inasmuch as it depends on the form but not on the position of the ourve which it represents.