217 and 218. These are parts of the same movement, which has been used for giving the roller motion in wool-combing machines. The roller to which wheel, F (218), is secured is required to make one third a revolution backward, then two thirds of a revolution forward, when it must stop until another length of combed fiber is ready for delivery. This is accomplished by the grooved heart-cam, C, D, B, e (217), the stud, A, working in the said groove; from C to D it moves the roller backward, and from D to e it moves it forward, the motion being transmitted through the catch, G, to the notch-wheel, F, on the roller-shaft, H. When the stud, A, arrives at the point, e, in the cam, a projection at the back of the wheel which carries the cam strikes the projecting piece on the catch, G, and raises it out of the notch in the wheel, F, so that, while the stud is traveling in the cam from e to C, the catch is passing over the plain surface between the two notches in the wheel, F, without imparting any motion; but when stud, A, arrives at the part, C, the catch has dropped in another notch, and is again ready to move wheel, F, and roller as required.