In the first place, the rider is placed over the main wheel, as in the bicycle, but much further forward. There are around him, on or near the ground, four little wheels, two before and two behind, supported in a manner the ingenuity of which calls for the utmost admiration. Turning the steering handle not only causes the front and rear pairs to turn opposite ways, but owing to their swiveling about an inward pointing axis, the machine is compelled to lean over toward the inside of the curve; not only is this the case, but each pair rises and falls with every inequality of the road, if the rider chooses that they run on the ground; but he can, if he pleases, arrange that in general they ride in the air, any one touching at such times as are necessary to keep him on the top of the one wheel, on which alone he is practically riding. He can, if he likes, at any time lift the main wheel off the ground and run along on the others only. The very few machines of the kind which I have seen have been provided with foot straps, to enable the rider to pull as well as push, which is a great advantage when climbing a hill, but this is on every machine except the Otto, of which I shall speak later, considered a dangerous practice. Some of the objections to the bicycle to which I have referred were sufficient to prevent many, especially elderly men, from dreaming of becoming cyclists. So long as the tricycle was a crude and clumsy machine, there was no chance of cycling becoming a part, as it almost is and certainly soon will be, of our national life. The tricycle has been brought to such a state of perfection that it is difficult to imagine where further progress can be made. Perhaps it will be well to mention what is necessary in order that a three-wheeled machine may be made to roll freely in a straight line, and also round curves. At all times each wheel must be able to travel in its own plane in spite of the united action of the other two. To run straight, the axes of all the wheels must obviously be parallel. To run round a curve, the axis of each must, if continued, pass through the center of curvature of the curve. If two wheels have a common axis, the intersection of the two lines forming the axes can only meet in one point. To steer such a combination, therefore, the plane of the third wheel only need be turned. If the axis of no two are common, then the planes of two of the wheels must be turned in order that the three axes may meet in a point. Not only does free rolling depend on the suitable direction of the planes of the wheels, each wheel must be able to run at a speed proportional to its distance from the point of intersection of the three axes, i.e., from the ever-shifting center of curvature.