I. Let me first notice the results obtained with the first class of bodies. These, again, are reducible to two forms. The Od-subject may either be of a regular figure and equal thickness throughout—as a piece of money, for instance; or it may be of an irregular figure, with an unequal mass of matter at one part—as, for instance, when it consists of an aggregate of several pieces of money variously arranged. I shall first treat of the first and simpler case. * * * * * It does not matter how you face in making these experiments. The influence of your person makes the various meridians of the Od-subject. The movements which we have first to examine are the results of holding the odometer over the middle of various uniform discs, such as I have supposed. They consist of two series of oscillations—one directed longitudinally to and from the experimenter; the other transversal, or in a plane at right angles to the plane of the first series of oscillations. Then it is highly convenient to have terms denoting the four cardinal points at which these oscillations cut the edge of the circular disc. These points may be termed _distal_, _proximal_, _dextral_, _sinistral_. It will likewise be found convenient to have terms to denote the direction of the motions manifested. The terms _distad_, _proximad_, _dextrad_, _sinistrad_, will serve our purpose. These terms refer to the person of the experimenter. Two other terms are still wanting; sometimes rotatory motion supervenes, which maybe either in the direction of the motion of the hands of a watch, or the reverse. I call the first of these two motions _clock-rotation_, the second _versed-rotation_. The present class of Od-subjects present the following remarkable differences among themselves:— Over one class, including gold, zinc, and polished glass, a circular mass of bicarbonate of soda, the odometer primarily oscillates _longitudinally_. With the other class, which includes pearl, ground glass, copper, a circular mass of tartaric acid, the odometer held over the centre primarily oscillates _transversely_. Over polished glass, an odometer of resin oscillates transversely; over ground glass longitudinally. Each of these movements is replaced by the other, when the thumb is brought into contact with the odometer-finger. (See figs. 1 and 2, in which the continuous line represents the primary motion; the dotted line, the secondary or complementary or reversed motion.) * * * * * II. Analysis of the forces, or currents conducing to, or implicated in the movements of the odometer just described. It has been said that the above movements manifest themselves when the odometer is held over the centre of the Od-subject. Let us now examine the consequences of holding the odometer extra-marginally to, or beyond the edge of, the Od-subject. [Illustration: Diagram showing figs. 1-8] [Illustration: Diagram showing figs. 9-14]