When the short lines upon the curve are close together, it shows that the saddle and rider are being checked proportionately as these lines are less than one-eighth of an inch apart. On the other hand, when the normal pace of the momentum of the heavier parts is slower than that of the wheels, it is shown by the lines being more than an eighth of an inch apart. In this case there is a tendency to increase the momentum instead of decreasing it,—a state of affairs not so much to be deplored if it were not evident that it is equally checked at some other point. We know, in practice with the Ordinary, that the loss of momentum by sudden checking can only happen to the full extent when the pace is reasonably slow; should the momentum be too great it will simply refuse to be interfered with in its forward course, and the rear wheel will leave the ground with a result and in a manner quite well known. In the safer forms of bicycles,—those from which a header is improbable,—without proper springs, the rider will simply slide forward on the saddle, causing considerable loss of momentum besides that due to vibration, since he must afterwards slide himself back again. Referring to the diagrams, Fig. 1 shows the Ordinary bicycle with a fifty-two-inch front and an eighteen-inch rear wheel. The front wheel mounts the obstacle with some difficulty, the curve upward being rather sudden in its change of direction from the base line, thus showing that the momentum is checked very rapidly; see the short vertical lines upon the curves, which are about one-half the distance apart of those on the base line between the curves and at the ends. Also notice that _F_ (the front wheel) carries three-fourths of the weight, one curve being about three times as high as the other. Particular attention is called to the easy and gradual curve shown by the mounting of the small rear wheel _R_; it would seem to show that the great clamor of theorists for large rear wheels in the Ordinary is somewhat unwarranted; the drop down and back in rolling off the obstacle will be seen to be quite sudden, but notice not very much more so than in Fig. 2, which shows the Rational, so called, with a fifty-two-inch driver and twenty-four-inch rear wheel. The large rear wheel affects the drop to some extent, but in all obstacles under four inches in height there is no perceptible benefit derived, at least not such as to warrant the extra weight and disarrangement of the steering.